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Analytical and Bioanalytical Chemistry (v.384, #1)
Analytical and bioanalytical chemistry in white waters: 2006 and beyond
by Sylvia Daunert (pp. 1-3).
Analytical and bioanalytical chemistry in white waters: 2006 and beyond
by Sylvia Daunert (pp. 1-3).
Sharing instrumentation globally
by Alanah Fitch; Ward Mavura; Michael Kishimba; Alice Muriithi (pp. 7-10).
Sharing instrumentation globally
by Alanah Fitch; Ward Mavura; Michael Kishimba; Alice Muriithi (pp. 7-10).
K.C. Thompson, C.P. Nathanail: Chemical analysis of contaminated land
by Helene Budzinski; Philippe Garrigues (pp. 21-21).
K.C. Thompson, C.P. Nathanail: Chemical analysis of contaminated land
by Helene Budzinski; Philippe Garrigues (pp. 21-21).
C. Chan, H. Lam, Y.C. Lee, X.-M. Zhang (eds): Analytical method validation and instrument performance verification
by Thomas Lazar (pp. 22-23).
C. Chan, H. Lam, Y.C. Lee, X.-M. Zhang (eds): Analytical method validation and instrument performance verification
by Thomas Lazar (pp. 22-23).
Ultrasensitive and rapid nanodevices for analytical immunoassays
by Maria Magliulo; Elisa Michelini; Patrizia Simoni; Massimo Guardigli; Aldo Roda (pp. 27-30).
Ultrasensitive and rapid nanodevices for analytical immunoassays
by Maria Magliulo; Elisa Michelini; Patrizia Simoni; Massimo Guardigli; Aldo Roda (pp. 27-30).
Micellar electrokinetic chromatography–mass spectrometry: combining the supposedly incompatible
by Govert W. Somsen; Roelof Mol; Gerhardus J. de Jong (pp. 31-33).
Micellar electrokinetic chromatography–mass spectrometry: combining the supposedly incompatible
by Govert W. Somsen; Roelof Mol; Gerhardus J. de Jong (pp. 31-33).
On-chip sample preconcentration for integrated microfluidic analysis
by Simon Song; Anup K. Singh (pp. 41-43).
On-chip sample preconcentration for integrated microfluidic analysis
by Simon Song; Anup K. Singh (pp. 41-43).
Glow discharge spectroscopy for depth profile analysis: from micrometer to sub-nanometer layers
by Jorge Pisonero (pp. 47-49).
Glow discharge spectroscopy for depth profile analysis: from micrometer to sub-nanometer layers
by Jorge Pisonero (pp. 47-49).
Miniaturization of an analytical system using immobilized biomolecules for high-throughput screening
by Masaru Kato; Kumoko Saka-Kato; Toshimasa Toyo’oka (pp. 50-52).
Miniaturization of an analytical system using immobilized biomolecules for high-throughput screening
by Masaru Kato; Kumoko Saka-Kato; Toshimasa Toyo’oka (pp. 50-52).
Separation science in perfume analysis
by Carlo Bicchi; Patrizia Rubiolo; Chiara Cordero (pp. 53-56).
Separation science in perfume analysis
by Carlo Bicchi; Patrizia Rubiolo; Chiara Cordero (pp. 53-56).
Chemoinformatics: a new field with a long tradition by Johann Gasteiger (pp. 57-64).
Chemoinformatics is the application of informatics methods to solve chemical problems. Although this term was introduced only a few years ago, this field has a long history with its roots going back more than 40 years. Work on chemical structure representation and searching, quantitative structure–activity relationships, chemometrics, molecular modeling as well as computer-assisted structure elucidation and synthesis design was initiated in the 1960s. These different origins have now merged into a discipline of its own that is in full bloom. All areas of chemistry from analytical chemistry to drug design can benefit from chemoinformatics methods. And there are still many challenging chemical problems waiting for solutions through the further development of chemoinformatics.
Keywords: Chemical structure representation; Property prediction; Chemometrics; Drug design; Structure elucidation; Synthesis design
Chemoinformatics: a new field with a long tradition by Johann Gasteiger (pp. 57-64).
Chemoinformatics is the application of informatics methods to solve chemical problems. Although this term was introduced only a few years ago, this field has a long history with its roots going back more than 40 years. Work on chemical structure representation and searching, quantitative structure–activity relationships, chemometrics, molecular modeling as well as computer-assisted structure elucidation and synthesis design was initiated in the 1960s. These different origins have now merged into a discipline of its own that is in full bloom. All areas of chemistry from analytical chemistry to drug design can benefit from chemoinformatics methods. And there are still many challenging chemical problems waiting for solutions through the further development of chemoinformatics.
Keywords: Chemical structure representation; Property prediction; Chemometrics; Drug design; Structure elucidation; Synthesis design
Enhancing the blood compatibility of ion-selective electrodes by Vasilis G. Gavalas; Maria J. Berrocal; Leonidas G. Bachas (pp. 65-72).
In vivo monitoring of various analytes is important for many bioanalytical and biomedical applications. The crucial challenge in this type of applications is the interaction of the sensor with the host environment, which is qualitatively described by the term biocompatibility. This review discusses recent advances in methods and materials used for the improvement of the biocompatibility of ion-selective electrodes especially as it relates to their interaction with blood components.
Keywords: Ion-selective electrodes; Biocompatibility; Hemocompatibility; Blood–membrane interactions
Enhancing the blood compatibility of ion-selective electrodes by Vasilis G. Gavalas; Maria J. Berrocal; Leonidas G. Bachas (pp. 65-72).
In vivo monitoring of various analytes is important for many bioanalytical and biomedical applications. The crucial challenge in this type of applications is the interaction of the sensor with the host environment, which is qualitatively described by the term biocompatibility. This review discusses recent advances in methods and materials used for the improvement of the biocompatibility of ion-selective electrodes especially as it relates to their interaction with blood components.
Keywords: Ion-selective electrodes; Biocompatibility; Hemocompatibility; Blood–membrane interactions
Bacillus anthracis: toxicology, epidemiology and current rapid-detection methods by Katie A. Edwards; Harriet A. Clancy; Antje J. Baeumner (pp. 73-84).
B. anthracis, the causative agent for anthrax, has been well studied for over 150 years. Due to the genetic similarities among various Bacillus species, as well as its existence in both a spore form and a vegetative state, the detection and specific identification of B. anthracis have been proven to require complex techniques and/or laborious methods. With the heightened interest in the organism as a potential biological threat agent, a large number of interesting detection technologies have recently been developed, including methods involving immunological and nucleic acid-based assay formats. The technologies range from culture-based methods to portable Total Analysis Systems based on real-time PCR. This review with 170 references provides a brief background on the toxicology and epidemiology of B. anthracis, discusses challenges associated with its detection related to genetic similarities to other species, and reviews immunological and, with greater emphasis, nucleic acid-based detection systems.
Keywords: Bacillus anthracis ; Detection; Biosensor; Toxicology; Epidemiology; Review
Bacillus anthracis: toxicology, epidemiology and current rapid-detection methods by Katie A. Edwards; Harriet A. Clancy; Antje J. Baeumner (pp. 73-84).
B. anthracis, the causative agent for anthrax, has been well studied for over 150 years. Due to the genetic similarities among various Bacillus species, as well as its existence in both a spore form and a vegetative state, the detection and specific identification of B. anthracis have been proven to require complex techniques and/or laborious methods. With the heightened interest in the organism as a potential biological threat agent, a large number of interesting detection technologies have recently been developed, including methods involving immunological and nucleic acid-based assay formats. The technologies range from culture-based methods to portable Total Analysis Systems based on real-time PCR. This review with 170 references provides a brief background on the toxicology and epidemiology of B. anthracis, discusses challenges associated with its detection related to genetic similarities to other species, and reviews immunological and, with greater emphasis, nucleic acid-based detection systems.
Keywords: Bacillus anthracis ; Detection; Biosensor; Toxicology; Epidemiology; Review
From fundamentals to applications: recent developments in atmospheric pressure photoionization mass spectrometry by Suzanne J. Bos; Suze M. van Leeuwen; Uwe Karst (pp. 85-99).
Only five years after the first publication on atmospheric pressure photoionization (APPI), this technique has evolved rapidly as a very useful complement to established ionization techniques for liquid chromatography/mass spectrometry (LC/MS). This is reflected in a rapidly increasing number of publications in this field. On the one hand, thorough studies into the photoionization mechanism have provided deep insights into the roles and influences of the solvent, the dopant and other additives. On the other hand, a large number of new and attractive applications have recently been introduced. New instrumental developments have resulted in combined APPI/ESI (PAESI) and APPI/APCI sources and a microfabricated APPI source. In this review, the most important developments within the field are summarized, focusing in particular on the applications of the technique.
Keywords: Photoionization; Atmospheric pressure photoionization; Liquid chromatography/mass spectrometry; Photoionization mechanism
From fundamentals to applications: recent developments in atmospheric pressure photoionization mass spectrometry by Suzanne J. Bos; Suze M. van Leeuwen; Uwe Karst (pp. 85-99).
Only five years after the first publication on atmospheric pressure photoionization (APPI), this technique has evolved rapidly as a very useful complement to established ionization techniques for liquid chromatography/mass spectrometry (LC/MS). This is reflected in a rapidly increasing number of publications in this field. On the one hand, thorough studies into the photoionization mechanism have provided deep insights into the roles and influences of the solvent, the dopant and other additives. On the other hand, a large number of new and attractive applications have recently been introduced. New instrumental developments have resulted in combined APPI/ESI (PAESI) and APPI/APCI sources and a microfabricated APPI source. In this review, the most important developments within the field are summarized, focusing in particular on the applications of the technique.
Keywords: Photoionization; Atmospheric pressure photoionization; Liquid chromatography/mass spectrometry; Photoionization mechanism
Raman spectroscopy in astrobiology by Susana E. Jorge Villar; Howell G. M. Edwards (pp. 100-113).
Raman spectroscopy is proposed as a valuable analytical technique for planetary exploration because it is sensitive to organic and inorganic compounds and able to unambiguously identify key spectral markers in a mixture of biological and geological components; furthermore, sample manipulation is not required and any size of sample can be studied without chemical or mechanical pretreatment. NASA and ESA are considering the adoption of miniaturised Raman spectrometers for inclusion in suites of analytical instrumentation to be placed on robotic landers on Mars in the near future to search for extinct or extant life signals. In this paper we review the advantages and limitations of Raman spectroscopy for the analysis of complex specimens with relevance to the detection of bio- and geomarkers in extremophilic organisms which are considered to be terrestrial analogues of possible extraterrestial life that could have developed on planetary surfaces.
Keywords: Raman spectroscopy; Astrobiology; Extremophile; Biomarkers; Geomarkers
Raman spectroscopy in astrobiology by Susana E. Jorge Villar; Howell G. M. Edwards (pp. 100-113).
Raman spectroscopy is proposed as a valuable analytical technique for planetary exploration because it is sensitive to organic and inorganic compounds and able to unambiguously identify key spectral markers in a mixture of biological and geological components; furthermore, sample manipulation is not required and any size of sample can be studied without chemical or mechanical pretreatment. NASA and ESA are considering the adoption of miniaturised Raman spectrometers for inclusion in suites of analytical instrumentation to be placed on robotic landers on Mars in the near future to search for extinct or extant life signals. In this paper we review the advantages and limitations of Raman spectroscopy for the analysis of complex specimens with relevance to the detection of bio- and geomarkers in extremophilic organisms which are considered to be terrestrial analogues of possible extraterrestial life that could have developed on planetary surfaces.
Keywords: Raman spectroscopy; Astrobiology; Extremophile; Biomarkers; Geomarkers
Microorganisms in inorganic chemical analysis by Beata Godlewska-Żyłkiewicz (pp. 114-123).
There are innumerable strains of microbes (bacteria, yeast and fungi) that degrade or transform chemicals and compounds into simpler, safer or less toxic substances. These bioprocesses have been used for centuries in the treatment of municipal wastes, in wine, cheese and bread making, and in bioleaching and metal recovery processes. Recent literature shows that microorganisms can be also used as effective sorbents for solid phase extraction procedures. This review reveals that fundamental nonanalytical studies on the parameters and conditions of biosorption processes and on metal–biomass interactions often result in efficient analytical procedures and biotechnological applications. Some selected examples illustrate the latest developments in the biosorption of metals by microbial biomass, which have opened the door to the application of microorganisms to analyte preconcentration, matrix separation and speciation analysis.
Keywords: Biosorption; Microorganisms; Trace metals; Preconcentration/separation; Speciation
Microorganisms in inorganic chemical analysis by Beata Godlewska-Żyłkiewicz (pp. 114-123).
There are innumerable strains of microbes (bacteria, yeast and fungi) that degrade or transform chemicals and compounds into simpler, safer or less toxic substances. These bioprocesses have been used for centuries in the treatment of municipal wastes, in wine, cheese and bread making, and in bioleaching and metal recovery processes. Recent literature shows that microorganisms can be also used as effective sorbents for solid phase extraction procedures. This review reveals that fundamental nonanalytical studies on the parameters and conditions of biosorption processes and on metal–biomass interactions often result in efficient analytical procedures and biotechnological applications. Some selected examples illustrate the latest developments in the biosorption of metals by microbial biomass, which have opened the door to the application of microorganisms to analyte preconcentration, matrix separation and speciation analysis.
Keywords: Biosorption; Microorganisms; Trace metals; Preconcentration/separation; Speciation
The clinical chemistry laboratory: current status, problems and diagnostic prospects by Erwin Schleicher (pp. 124-131).
Although increased automation, advanced analytical techniques and sophisticated information technology have greatly improved the performance and quality in medical laboratory testing, several studies show that significant amounts of errors occur. Detailed analysis revealed that most of the errors occur in the preanalytical phase, while fewer errors occur in the intra- and post-analytical phase. The majority of errors are caused by wrong sampling or occur during transport to the laboratory. This review focuses on the analytical procedures in a large central laboratory. Possible problems are described by following samples from the patient to the laboratory and back. Finally, the advantages and disadvantages of point-of-care testing versus central laboratory are compared.
Keywords: Errors; Problems; Laboratory medicine; Selectivity; POCT
The clinical chemistry laboratory: current status, problems and diagnostic prospects by Erwin Schleicher (pp. 124-131).
Although increased automation, advanced analytical techniques and sophisticated information technology have greatly improved the performance and quality in medical laboratory testing, several studies show that significant amounts of errors occur. Detailed analysis revealed that most of the errors occur in the preanalytical phase, while fewer errors occur in the intra- and post-analytical phase. The majority of errors are caused by wrong sampling or occur during transport to the laboratory. This review focuses on the analytical procedures in a large central laboratory. Possible problems are described by following samples from the patient to the laboratory and back. Finally, the advantages and disadvantages of point-of-care testing versus central laboratory are compared.
Keywords: Errors; Problems; Laboratory medicine; Selectivity; POCT
CE determination of small ions: methods and techniques by Audrius Padarauskas (pp. 132-144).
This paper provides an overview on the current status of capillary electrophoresis (CE) in the analysis of inorganic and charged small organic species. The various CE strategies used to improve the separation of ionic analytes are summarized. Technical developments in the design of improved detection systems are described. A brief account of their advantages and limitations is given. The potential use of these devices for miniaturized CE systems is also described. Finally, special attention is focused on the on-capillary preconcentration techniques developed in attempts to overcome the poor detectability of CE. Recent review articles are frequently cited to provide readers with a source of information about pioneering work, theoretical treatments, and specific applications.
Keywords: Capillary electrophoresis; Small ions; Separation principles; Detection; Preconcentration
CE determination of small ions: methods and techniques by Audrius Padarauskas (pp. 132-144).
This paper provides an overview on the current status of capillary electrophoresis (CE) in the analysis of inorganic and charged small organic species. The various CE strategies used to improve the separation of ionic analytes are summarized. Technical developments in the design of improved detection systems are described. A brief account of their advantages and limitations is given. The potential use of these devices for miniaturized CE systems is also described. Finally, special attention is focused on the on-capillary preconcentration techniques developed in attempts to overcome the poor detectability of CE. Recent review articles are frequently cited to provide readers with a source of information about pioneering work, theoretical treatments, and specific applications.
Keywords: Capillary electrophoresis; Small ions; Separation principles; Detection; Preconcentration
Delimitation of squamous cell cervical carcinoma using infrared microspectroscopic imaging by Wolfram Steller; Jens Einenkel; Lars-Christian Horn; Ulf-Dietrich Braumann; Hans Binder; Reiner Salzer; Christoph Krafft (pp. 145-154).
Infrared (IR) spectroscopic imaging coupled with microscopy has been used to investigate thin sections of cervix uteri encompassing normal tissue, precancerous structures, and squamous cell carcinoma. Methods for unsupervised distinction of tissue types based on IR spectroscopy were developed. One-hundred and twenty-two images of cervical tissue were recorded by an FTIR spectrometer with a 64×64 focal plane array detector. The 499,712 IR spectra obtained were grouped by an approach which used fuzzy C-means clustering followed by hierarchical cluster analysis. The resulting false color maps were correlated with the morphological characteristics of an adjacent section of hematoxylin and eosin-stained tissue. In the first step, cervical stroma, epithelium, inflammation, blood vessels, and mucus could be distinguished in IR images by analysis of the spectral fingerprint region (950–1480 cm−1). In the second step, analysis in the spectral window 1420–1480 cm−1 enables, for the first time, IR spectroscopic distinction between the basal layer, dysplastic lesions and squamous cell carcinoma within a particular sample. The joint application of IR microspectroscopic imaging and multivariate spectral processing combines diffraction-limited lateral optical resolution on the single cell level with highly specific and sensitive spectral classification on the molecular level. Compared with previous reports our approach constitutes a significant progress in the development of optical molecular spectroscopic techniques toward an additional diagnostic tool for the early histopathological characterization of cervical cancer.
Keywords: Cervix uteri; Squamous cell carcinoma; Infrared imaging; Cluster analysis; Tissue classification
Delimitation of squamous cell cervical carcinoma using infrared microspectroscopic imaging by Wolfram Steller; Jens Einenkel; Lars-Christian Horn; Ulf-Dietrich Braumann; Hans Binder; Reiner Salzer; Christoph Krafft (pp. 145-154).
Infrared (IR) spectroscopic imaging coupled with microscopy has been used to investigate thin sections of cervix uteri encompassing normal tissue, precancerous structures, and squamous cell carcinoma. Methods for unsupervised distinction of tissue types based on IR spectroscopy were developed. One-hundred and twenty-two images of cervical tissue were recorded by an FTIR spectrometer with a 64×64 focal plane array detector. The 499,712 IR spectra obtained were grouped by an approach which used fuzzy C-means clustering followed by hierarchical cluster analysis. The resulting false color maps were correlated with the morphological characteristics of an adjacent section of hematoxylin and eosin-stained tissue. In the first step, cervical stroma, epithelium, inflammation, blood vessels, and mucus could be distinguished in IR images by analysis of the spectral fingerprint region (950–1480 cm−1). In the second step, analysis in the spectral window 1420–1480 cm−1 enables, for the first time, IR spectroscopic distinction between the basal layer, dysplastic lesions and squamous cell carcinoma within a particular sample. The joint application of IR microspectroscopic imaging and multivariate spectral processing combines diffraction-limited lateral optical resolution on the single cell level with highly specific and sensitive spectral classification on the molecular level. Compared with previous reports our approach constitutes a significant progress in the development of optical molecular spectroscopic techniques toward an additional diagnostic tool for the early histopathological characterization of cervical cancer.
Keywords: Cervix uteri; Squamous cell carcinoma; Infrared imaging; Cluster analysis; Tissue classification
Absorption and scattering characterization of airborne microparticulates by a cavity ringdown technique by Valery Bulatov; Yuheng Chen; Aktam Khalmanov; Israel Schechter (pp. 155-160).
Nonresonant cavity ringdown laser absorption spectroscopy (CRLAS) was applied for detection and characterization of airborne particulates. Sensitive detection of a variety of aerosols under ambient conditions was achieved. The method provides, for the first time, time-resolved absolute aerosol concentration, with spatial resolution (along a line). The first report on absorption spectroscopy of monodispersed aerosols (in the size range 100–200 nm) is provided, and comparisons are made with the bulk data. The results indicate the possibility of applying CRLAS for selective analysis of aerosols. A new method for estimating the aerosol refraction index is also obtained from the ringdown data.
Keywords: Cavity ringdown; Aerosols; Laser Spectroscopy
Absorption and scattering characterization of airborne microparticulates by a cavity ringdown technique by Valery Bulatov; Yuheng Chen; Aktam Khalmanov; Israel Schechter (pp. 155-160).
Nonresonant cavity ringdown laser absorption spectroscopy (CRLAS) was applied for detection and characterization of airborne particulates. Sensitive detection of a variety of aerosols under ambient conditions was achieved. The method provides, for the first time, time-resolved absolute aerosol concentration, with spatial resolution (along a line). The first report on absorption spectroscopy of monodispersed aerosols (in the size range 100–200 nm) is provided, and comparisons are made with the bulk data. The results indicate the possibility of applying CRLAS for selective analysis of aerosols. A new method for estimating the aerosol refraction index is also obtained from the ringdown data.
Keywords: Cavity ringdown; Aerosols; Laser Spectroscopy
A new approach for fast, simultaneous NO/NO2 analysis: application of basic features of multiphoton-induced ionization and dissociation of NOx by A. Bornschlegl; R. Weishaeupl; U. Boesl (pp. 161-168).
A new method of simultaneously recording NO and NO2 concentrations in complex gas mixtures is described. This method is based on resonance enhanced multiphoton ionization (REMPI), on time-of-flight mass analysis, and on monitoring the kinetic energy released upon dissociation of NO2. Its benefits are high speed and high flexibility. NO/NO2 analysis can therefore be combined with the simultaneous monitoring of other components. For instance, NH3 is a compound of interest when studying the chemical reactions of NOx in catalytic converters of combustion engines. The spectroscopic excitation schemes used for this new method are discussed in detail. Its reliability has been demonstrated by performing measurements at an industrial motor test facility. This novel technique performs well in comparison with conventional NOx analysis using chemiluminescence detection. Figure NOx-analysis of Diesel engine exhaust. Simultaneous fast detection of NO and NO2 by LAMS (laser mass spectrometry). Comparison of LAMS(NOx) with conventional CLD (chemiluminescence detection)
Keywords: NOx analysis; Fast chemical analysis; Resonance enhanced multiphoton ionization; Kinetic energy release; Laser mass spectrometry
A new approach for fast, simultaneous NO/NO2 analysis: application of basic features of multiphoton-induced ionization and dissociation of NOx by A. Bornschlegl; R. Weishaeupl; U. Boesl (pp. 161-168).
A new method of simultaneously recording NO and NO2 concentrations in complex gas mixtures is described. This method is based on resonance enhanced multiphoton ionization (REMPI), on time-of-flight mass analysis, and on monitoring the kinetic energy released upon dissociation of NO2. Its benefits are high speed and high flexibility. NO/NO2 analysis can therefore be combined with the simultaneous monitoring of other components. For instance, NH3 is a compound of interest when studying the chemical reactions of NOx in catalytic converters of combustion engines. The spectroscopic excitation schemes used for this new method are discussed in detail. Its reliability has been demonstrated by performing measurements at an industrial motor test facility. This novel technique performs well in comparison with conventional NOx analysis using chemiluminescence detection. Figure NOx-analysis of Diesel engine exhaust. Simultaneous fast detection of NO and NO2 by LAMS (laser mass spectrometry). Comparison of LAMS(NOx) with conventional CLD (chemiluminescence detection)
Keywords: NOx analysis; Fast chemical analysis; Resonance enhanced multiphoton ionization; Kinetic energy release; Laser mass spectrometry
On-column labeling for capillary electrophoretic analysis of individual mitochondria directly sampled from tissue cross sections by Hossein Ahmadzadeh; LaDora V. Thompson; Edgar A. Arriaga (pp. 169-174).
This technical note reports on a new procedure to on-column-label organelles sampled from a tissue cross section into a fused silica capillary. These organelles are then analyzed by capillary electrophoresis with postcolumn laser-induced fluorescence detection. In this procedure, the fluorescent label does not come in contact with the tissue, which facilitates visualization of the sampled tissue cross section. In addition, on-column labeling allows for better control of the reaction time and fluorescent label concentrations. As a proof-of-principle, we show results of mitochondria from rat gastrocnemius muscle cross sections that were on-column-labeled with 10-N-nonyl acridine orange (NAO), a mitochondrion-specific probe, and compare them with results for NAO in-tissue labeling of the same tissue. The new organelle labeling procedure reported here may easily be extended to the analysis of individual organelles in other biological samples and may become a valuable tool in studies investigating the role of mitochondria in muscle aging and exercise physiology.
Keywords: On-column labeling; Capillary electrophoresis; Fluorescence; Mitochondria; Muscle
On-column labeling for capillary electrophoretic analysis of individual mitochondria directly sampled from tissue cross sections by Hossein Ahmadzadeh; LaDora V. Thompson; Edgar A. Arriaga (pp. 169-174).
This technical note reports on a new procedure to on-column-label organelles sampled from a tissue cross section into a fused silica capillary. These organelles are then analyzed by capillary electrophoresis with postcolumn laser-induced fluorescence detection. In this procedure, the fluorescent label does not come in contact with the tissue, which facilitates visualization of the sampled tissue cross section. In addition, on-column labeling allows for better control of the reaction time and fluorescent label concentrations. As a proof-of-principle, we show results of mitochondria from rat gastrocnemius muscle cross sections that were on-column-labeled with 10-N-nonyl acridine orange (NAO), a mitochondrion-specific probe, and compare them with results for NAO in-tissue labeling of the same tissue. The new organelle labeling procedure reported here may easily be extended to the analysis of individual organelles in other biological samples and may become a valuable tool in studies investigating the role of mitochondria in muscle aging and exercise physiology.
Keywords: On-column labeling; Capillary electrophoresis; Fluorescence; Mitochondria; Muscle
A fluorescence-based microplate assay to quantify DOM-induced catabolic activity by Y. Dudal; R. Holgado; K. Knoth; M. Debroux (pp. 175-179).
This note describes a novel method to quickly quantify the dissolved organic matter (DOM)-induced catabolic activity from low-volume samples. The concept is based on the catabolic response profiles (CRP) assay and is described as an inverse CRP, where the reactivity of a complex and diverse mixture of organic compounds towards single strains of bacteria is quantified. A strain of Pseudomonas fluorescens was grown and then transferred to an organic carbon-free mineral salt medium. 90 μL of a fluorogenic redox indicator was added to 90 μL of the bacterial suspension in a well on a 96-well microplate. The DOM sample (90 μL) was added to the well and the fluorescence emitted by the reduced indicator was read over the period of incubation. Only 0.8 mL of the DOM sample, including controls and replicates, was required to quantify the activity of each sample. Results are presented for a surface soil DOM sample and they were compared to glucose samples of various concentrations. The detection limit was reached for samples containing as little as 55 μM of glucose (0.3 mg C L−1). The assay showed that only 9% of the total carbon of the soil surface DOM sample was readily biodegradable.
A fluorescence-based microplate assay to quantify DOM-induced catabolic activity by Y. Dudal; R. Holgado; K. Knoth; M. Debroux (pp. 175-179).
This note describes a novel method to quickly quantify the dissolved organic matter (DOM)-induced catabolic activity from low-volume samples. The concept is based on the catabolic response profiles (CRP) assay and is described as an inverse CRP, where the reactivity of a complex and diverse mixture of organic compounds towards single strains of bacteria is quantified. A strain of Pseudomonas fluorescens was grown and then transferred to an organic carbon-free mineral salt medium. 90 μL of a fluorogenic redox indicator was added to 90 μL of the bacterial suspension in a well on a 96-well microplate. The DOM sample (90 μL) was added to the well and the fluorescence emitted by the reduced indicator was read over the period of incubation. Only 0.8 mL of the DOM sample, including controls and replicates, was required to quantify the activity of each sample. Results are presented for a surface soil DOM sample and they were compared to glucose samples of various concentrations. The detection limit was reached for samples containing as little as 55 μM of glucose (0.3 mg C L−1). The assay showed that only 9% of the total carbon of the soil surface DOM sample was readily biodegradable.
Optimizing integrated optical chips for label-free (bio-)chemical sensing by R. E. Kunz; K. Cottier (pp. 180-190).
Label-free sensing is an important method for many (bio-)chemical applications in fields such as biotechnology, medicine, pharma, ecology and food quality control. The broad range of applications includes liquid refractive index sensing, molecule detection, and the detection of particles or cells. Integrated optics based on the use of waveguide modes offers a great potential and flexibility to tailor the sensor properties to these applications. In this paper, the results of a numerical study are presented, showing that this flexibility is founded on the many degrees of freedom that can be used for the integrated optical chip design, in contrast to other technologies such as those based on surface plasmon resonance, for which the materials' properties limit the range of choices. The applications that are explicitly considered and discussed include (1) bulk refractometry, (2) thin-layer sensing, for example biosensors monitoring molecular adsorption processes occurring within some 10 nm of the chip's surface, (3) thick-layer sensing with processes involving molecules or ions to be monitored within a sensing matrix extending to some 100 nm from the chip's surface, for example hydrogel-based layers and chemo-optically sensitive membranes, and (4) particle sensing with particles or, for example, biological cells to be monitored within probe volumes extending to some 1,000 nm from the chip's surface. The peculiarities for the different types of applications will be discussed, and suitable modeling methods presented. Finally, the application-specific design guidelines supplied will enable the optimization of various types of integrated optical sensors, including interferometers and grating-based sensors.
Keywords: Label-free sensing; (Bio-)chemical sensors; Evanescent-wave sensors; Integrated optical sensor chip; Waveguides
Optimizing integrated optical chips for label-free (bio-)chemical sensing by R. E. Kunz; K. Cottier (pp. 180-190).
Label-free sensing is an important method for many (bio-)chemical applications in fields such as biotechnology, medicine, pharma, ecology and food quality control. The broad range of applications includes liquid refractive index sensing, molecule detection, and the detection of particles or cells. Integrated optics based on the use of waveguide modes offers a great potential and flexibility to tailor the sensor properties to these applications. In this paper, the results of a numerical study are presented, showing that this flexibility is founded on the many degrees of freedom that can be used for the integrated optical chip design, in contrast to other technologies such as those based on surface plasmon resonance, for which the materials' properties limit the range of choices. The applications that are explicitly considered and discussed include (1) bulk refractometry, (2) thin-layer sensing, for example biosensors monitoring molecular adsorption processes occurring within some 10 nm of the chip's surface, (3) thick-layer sensing with processes involving molecules or ions to be monitored within a sensing matrix extending to some 100 nm from the chip's surface, for example hydrogel-based layers and chemo-optically sensitive membranes, and (4) particle sensing with particles or, for example, biological cells to be monitored within probe volumes extending to some 1,000 nm from the chip's surface. The peculiarities for the different types of applications will be discussed, and suitable modeling methods presented. Finally, the application-specific design guidelines supplied will enable the optimization of various types of integrated optical sensors, including interferometers and grating-based sensors.
Keywords: Label-free sensing; (Bio-)chemical sensors; Evanescent-wave sensors; Integrated optical sensor chip; Waveguides
A microfluidic SELEX prototype by Glen Hybarger; Joseph Bynum; Robert F. Williams; James J. Valdes; James P. Chambers (pp. 191-198).
Aptamers are nucleic acid binding species capable of recognizing a wide variety of targets ranging from small organic molecules to supramolecular structures, including organisms. They are isolated from combinatorial libraries of synthetic nucleic acid by an iterative process referred to as SELEX (Systematic Evolution of Ligands by Exponential Enrichment). Here we describe an automated microfluidic, microline-based assembly that uses LabView-controlled actuatable valves and a PCR machine, and which is capable of the selection and synthesis of an anti-lysozyme aptamer as verified by sequence analysis. The microfluidic prototype described is 1) a simple apparatus that is relatively inexpensive to assemble, making automated aptamer selection accessible to many investigators, and 2) useful for the continued “morphing” of macro→meso→microfabricated structures until a convergence to a few functional systems evolves and emerges, partly or completely achieving simpler, smaller and more rapid SELEX applications.
Keywords: SELEX; Microfluidic; Miniaturized; Aptamer; Prototype
A microfluidic SELEX prototype by Glen Hybarger; Joseph Bynum; Robert F. Williams; James J. Valdes; James P. Chambers (pp. 191-198).
Aptamers are nucleic acid binding species capable of recognizing a wide variety of targets ranging from small organic molecules to supramolecular structures, including organisms. They are isolated from combinatorial libraries of synthetic nucleic acid by an iterative process referred to as SELEX (Systematic Evolution of Ligands by Exponential Enrichment). Here we describe an automated microfluidic, microline-based assembly that uses LabView-controlled actuatable valves and a PCR machine, and which is capable of the selection and synthesis of an anti-lysozyme aptamer as verified by sequence analysis. The microfluidic prototype described is 1) a simple apparatus that is relatively inexpensive to assemble, making automated aptamer selection accessible to many investigators, and 2) useful for the continued “morphing” of macro→meso→microfabricated structures until a convergence to a few functional systems evolves and emerges, partly or completely achieving simpler, smaller and more rapid SELEX applications.
Keywords: SELEX; Microfluidic; Miniaturized; Aptamer; Prototype
Development of a high-throughput method for the determination of itraconazole and its hydroxy metabolite in human plasma, employing automated liquid–liquid extraction based on 96-well format plates and LC/MS/MS by Constantinos Kousoulos; Georgia Tsatsou; Constantinos Apostolou; Yannis Dotsikas; Yannis L. Loukas (pp. 199-207).
A semi-automated liquid chromatography–tandem mass spectrometry (LC/MS/MS) method was developed for the simultaneous quantification of the antifungal drug itraconazole (ITZ) and its coactive metabolite hydroxyitraconazole (OH-ITZ) in human plasma. The plasma samples underwent liquid–liquid extraction (LLE) in 2.2 mL 96 deepwell plates. ITZ, OH-ITZ and the internal standard (IS) R51012 were extracted from plasma, using a mixture of acetonitrile (ACN) and methyl t-butyl ether (MTBE) as the organic solvent. This specific mixture, due to its composition, had a significant impact on the performance of the assay. All liquid transfer steps, including preparation of calibration standards and quality control samples as well as the addition of the IS, were performed automatically using robotic liquid handling workstations for parallel sample processing. After vortexing, centrifugation and freezing, the supernatant organic solvent was evaporated. The analytes and IS were dissolved in a small volume of a reconstitution solution, an aliquot of which was analyzed by combined reversed phase LC/MS/MS, with positive ion electrospray ionization and a TurboIonSpray interface, using multiple reactions monitoring (MRM). The method was shown to be sensitive and specific to both ITZ and OH-ITZ, it revealed excellent linearity for the range of concentrations 2–500 ng mL−1 for ITZ and 4–1000 ng mL−1 for OH-ITZ, it was very accurate and it gave very good inter- and intra-day precisions. The proposed high-throughput method was employed in a bioequivalence study after per os administration of two 100 mg tablets of ITZ, and it allowed this study to be completed in under four days.
Keywords: Itraconazole; Bioequivalence; Mass spectrometry; 96-well
Development of a high-throughput method for the determination of itraconazole and its hydroxy metabolite in human plasma, employing automated liquid–liquid extraction based on 96-well format plates and LC/MS/MS by Constantinos Kousoulos; Georgia Tsatsou; Constantinos Apostolou; Yannis Dotsikas; Yannis L. Loukas (pp. 199-207).
A semi-automated liquid chromatography–tandem mass spectrometry (LC/MS/MS) method was developed for the simultaneous quantification of the antifungal drug itraconazole (ITZ) and its coactive metabolite hydroxyitraconazole (OH-ITZ) in human plasma. The plasma samples underwent liquid–liquid extraction (LLE) in 2.2 mL 96 deepwell plates. ITZ, OH-ITZ and the internal standard (IS) R51012 were extracted from plasma, using a mixture of acetonitrile (ACN) and methyl t-butyl ether (MTBE) as the organic solvent. This specific mixture, due to its composition, had a significant impact on the performance of the assay. All liquid transfer steps, including preparation of calibration standards and quality control samples as well as the addition of the IS, were performed automatically using robotic liquid handling workstations for parallel sample processing. After vortexing, centrifugation and freezing, the supernatant organic solvent was evaporated. The analytes and IS were dissolved in a small volume of a reconstitution solution, an aliquot of which was analyzed by combined reversed phase LC/MS/MS, with positive ion electrospray ionization and a TurboIonSpray interface, using multiple reactions monitoring (MRM). The method was shown to be sensitive and specific to both ITZ and OH-ITZ, it revealed excellent linearity for the range of concentrations 2–500 ng mL−1 for ITZ and 4–1000 ng mL−1 for OH-ITZ, it was very accurate and it gave very good inter- and intra-day precisions. The proposed high-throughput method was employed in a bioequivalence study after per os administration of two 100 mg tablets of ITZ, and it allowed this study to be completed in under four days.
Keywords: Itraconazole; Bioequivalence; Mass spectrometry; 96-well
Determination of ibuprofen and tetrazepam in human urine by micellar electrokinetic capillary chromatography by J. J. Berzas Nevado; J. Rodríguez Flores; G. Castañeda Peñalvo; R. M. Rodríguez Dorado (pp. 208-214).
A new micellar electrokinetic capillary chromatography method (MEKC) is proposed for the determination of ibuprofen and tetrazepam in human urine samples over a concentration range of therapeutic interest. A fused silica capillary (60 cm × 75 μm) is used. Ibuprofen and tetrazepam are detected via UV detection at 220 and 228 nm, respectively. Separation is performed at 25 °C and at a separation voltage of 30 kV, with 15 mM borate buffer (pH 10.2) containing 40 mM sodium dodecylsulfate as the electrolyte solution. Under these conditions the analytes were separated in <11 min. Sulfamethazine is used as an internal standard. Prior to determination, the samples are purified and enriched by means of an extraction–preconcentration step with a preconditioned C18 cartridge and by eluting the compounds with methanol. Good linearity, accuracy, precision, robustness and solution stability were achieved for the technique. Detection limits of 200 μg L−1 for ibuprofen and 300 μg L−1 for tetrazepam were obtained. These analytes were then determined in real urine using the technique.
Keywords: Ibuprofen; Tetrazepam; Capillary electrophoresis; Robustness; Urine
Determination of ibuprofen and tetrazepam in human urine by micellar electrokinetic capillary chromatography by J. J. Berzas Nevado; J. Rodríguez Flores; G. Castañeda Peñalvo; R. M. Rodríguez Dorado (pp. 208-214).
A new micellar electrokinetic capillary chromatography method (MEKC) is proposed for the determination of ibuprofen and tetrazepam in human urine samples over a concentration range of therapeutic interest. A fused silica capillary (60 cm × 75 μm) is used. Ibuprofen and tetrazepam are detected via UV detection at 220 and 228 nm, respectively. Separation is performed at 25 °C and at a separation voltage of 30 kV, with 15 mM borate buffer (pH 10.2) containing 40 mM sodium dodecylsulfate as the electrolyte solution. Under these conditions the analytes were separated in <11 min. Sulfamethazine is used as an internal standard. Prior to determination, the samples are purified and enriched by means of an extraction–preconcentration step with a preconditioned C18 cartridge and by eluting the compounds with methanol. Good linearity, accuracy, precision, robustness and solution stability were achieved for the technique. Detection limits of 200 μg L−1 for ibuprofen and 300 μg L−1 for tetrazepam were obtained. These analytes were then determined in real urine using the technique.
Keywords: Ibuprofen; Tetrazepam; Capillary electrophoresis; Robustness; Urine
Pyridinium-based ionic liquid matrices can improve the identification of proteins by peptide mass-fingerprint analysis with matrix-assisted laser desorption/ionization mass spectrometry by Masoud Zabet-Moghaddam; Elmar Heinzle; Maria Lasaosa; Andreas Tholey (pp. 215-224).
Matrix-assisted laser desorption/ionization mass spectrometry has become an indispensable tool for identification of proteins by peptide mass-fingerprint analysis. Selection of the matrix, addition of matrix additives, and sample-preparation techniques are known to affect the quality of the spectra and hence protein identification. We investigated the effect of pyridine as matrix additive for the commonly used crystalline matrix α-cyano-4-hydroxycinnamic acid (CCA), forming a pyridinium based ionic liquid matrix, on the mass spectra of synthetic peptides and tryptic protein digests. Beside the equimolar mixture of CCA and pyridine, the effect of addition of substoichiometric amounts of the base to the acid was tested. Optimum results in terms of signal-to-noise ratios, reduction of chemical noise, and reduced formation of alkali adducts and matrix clusters were observed for the matrix CCA–pyridine in the molar ratio 2:1. The optimized ionic liquid matrix was used for identification of tryptic digests of six model proteins and for identification of a protein extracted from a two-dimensional gel with the proteome of the bacterium Corynebacterium glutamicum, and shown to facilitate protein identification, yielding higher scores and increased sequence coverage compared with pure CCA. Thus CCA–Py 2:1 is a potential alternative for identification and characterization of proteins by peptide mass-fingerprint analysis.
Keywords: Ionic liquid matrices; Limit of detection; Mass spectrometry; Matrix additives; Proteomics
Pyridinium-based ionic liquid matrices can improve the identification of proteins by peptide mass-fingerprint analysis with matrix-assisted laser desorption/ionization mass spectrometry by Masoud Zabet-Moghaddam; Elmar Heinzle; Maria Lasaosa; Andreas Tholey (pp. 215-224).
Matrix-assisted laser desorption/ionization mass spectrometry has become an indispensable tool for identification of proteins by peptide mass-fingerprint analysis. Selection of the matrix, addition of matrix additives, and sample-preparation techniques are known to affect the quality of the spectra and hence protein identification. We investigated the effect of pyridine as matrix additive for the commonly used crystalline matrix α-cyano-4-hydroxycinnamic acid (CCA), forming a pyridinium based ionic liquid matrix, on the mass spectra of synthetic peptides and tryptic protein digests. Beside the equimolar mixture of CCA and pyridine, the effect of addition of substoichiometric amounts of the base to the acid was tested. Optimum results in terms of signal-to-noise ratios, reduction of chemical noise, and reduced formation of alkali adducts and matrix clusters were observed for the matrix CCA–pyridine in the molar ratio 2:1. The optimized ionic liquid matrix was used for identification of tryptic digests of six model proteins and for identification of a protein extracted from a two-dimensional gel with the proteome of the bacterium Corynebacterium glutamicum, and shown to facilitate protein identification, yielding higher scores and increased sequence coverage compared with pure CCA. Thus CCA–Py 2:1 is a potential alternative for identification and characterization of proteins by peptide mass-fingerprint analysis.
Keywords: Ionic liquid matrices; Limit of detection; Mass spectrometry; Matrix additives; Proteomics
Synthesis of polyacrylamide gel beads with electrostatic functional groups for the molecular imprinting of bovine serum albumin by Xingshou Pang; Guoxiang Cheng; Shulai Lu; Erjun Tang (pp. 225-230).
Synthetic materials capable of recognizing proteins are important in separation, biosensors and biomaterials. In this study, bovine serum albumin-imprinted soft-wet polyacrylamide gel beads were prepared via inverse-phase suspension polymerization, using acrylamide and N,N′-methylene diacrylamide as polymeric matrix components and methacrylic acid as functional monomer. The adsorption study showed, through the imprinting process, that the imprinted gel beads had much higher adsorption capacity than the nonimprinted gel beads, and that the matching of the surface zeta-potential between the templates and the imprinted gel beads can enhance the imprinting effect. Adsorption kinetics indicated that the adsorption process could be described as an apparent first-order kinetic process for the gel beads. From the adsorption isotherm curve, we found that the adsorption of the imprinted gel beads was in agreement with the Langmuir adsorption model. Moreover, selectivity testing of the imprinted gel beads showed that imprinted gel beads exhibited good recognition for BSA as compared to the control protein. We speculate that the formation of complementary shapes and multiple-point electrostatic interactions between the imprinting cavities and the template proteins are the two factors that lead to the imprinting effect.
Keywords: Polyacrylamide gel beads; Bovine serum albumin; Molecular imprinting; Methacrylic acid
Synthesis of polyacrylamide gel beads with electrostatic functional groups for the molecular imprinting of bovine serum albumin by Xingshou Pang; Guoxiang Cheng; Shulai Lu; Erjun Tang (pp. 225-230).
Synthetic materials capable of recognizing proteins are important in separation, biosensors and biomaterials. In this study, bovine serum albumin-imprinted soft-wet polyacrylamide gel beads were prepared via inverse-phase suspension polymerization, using acrylamide and N,N′-methylene diacrylamide as polymeric matrix components and methacrylic acid as functional monomer. The adsorption study showed, through the imprinting process, that the imprinted gel beads had much higher adsorption capacity than the nonimprinted gel beads, and that the matching of the surface zeta-potential between the templates and the imprinted gel beads can enhance the imprinting effect. Adsorption kinetics indicated that the adsorption process could be described as an apparent first-order kinetic process for the gel beads. From the adsorption isotherm curve, we found that the adsorption of the imprinted gel beads was in agreement with the Langmuir adsorption model. Moreover, selectivity testing of the imprinted gel beads showed that imprinted gel beads exhibited good recognition for BSA as compared to the control protein. We speculate that the formation of complementary shapes and multiple-point electrostatic interactions between the imprinting cavities and the template proteins are the two factors that lead to the imprinting effect.
Keywords: Polyacrylamide gel beads; Bovine serum albumin; Molecular imprinting; Methacrylic acid
Two- and three-dimensional mapping of the iron distribution in the apoplastic fluid of plant leaf tissue by means of magnetic resonance imaging by Jörg Lambert; Peter Lampen; Alex von Bohlen; Roland Hergenröder (pp. 231-236).
A three-dimensional nuclear magnetic resonance imaging (MRI) technique for non-invasive mapping of iron in the apoplastic fluid of plant compartments was developed. The new technique was applied to a leaf of red stem dogwood (Cornus stolonifera). The results are compared with MRI measurements of iron distributions in two dimensions and with total reflection X-ray fluorescence results.
Keywords: Magnetic resonance imaging; Iron; Plant leaves; Apoplastic fluid
Two- and three-dimensional mapping of the iron distribution in the apoplastic fluid of plant leaf tissue by means of magnetic resonance imaging by Jörg Lambert; Peter Lampen; Alex von Bohlen; Roland Hergenröder (pp. 231-236).
A three-dimensional nuclear magnetic resonance imaging (MRI) technique for non-invasive mapping of iron in the apoplastic fluid of plant compartments was developed. The new technique was applied to a leaf of red stem dogwood (Cornus stolonifera). The results are compared with MRI measurements of iron distributions in two dimensions and with total reflection X-ray fluorescence results.
Keywords: Magnetic resonance imaging; Iron; Plant leaves; Apoplastic fluid
Establishing a chromium-reactor design for measuring δ2H values of solid polyhalogenated compounds using direct elemental analysis and stable isotope ratio mass spectrometry by Wolfgang Armbruster; Katja Lehnert; Walter Vetter (pp. 237-243).
2H/1H isotope ratios of polyhalogenated compounds were determined by elemental analysis and isotope ratio mass spectrometry (EA-IRMS). Initial measurements with standard EA-IRMS equipment, which used high-temperature pyrolysis to convert the organic compounds into hydrogen, did not achieve significant signals for polychlorinated pesticides and related compounds, presumably due to the formation of HCl instead of hydrogen. To reverse this problematic reaction, a chromium reactor was incorporated into the element analyzer system, which scavenged Cl, forming chromium chloride and releasing hydrogen again in the form of H2. The optimized system therefore allowed the δ2H values of polyhalogenated compounds to be determined. A quality assurance program was developed based on several parameters. (i) Each compound was analyzed using a sequence of five injections, where the first measurement was discarded. (ii) Recovery of H (when calculated relative to acetanilide) had to be >90% for all replicates in a sequence. (iii) All δ-values within a sequence had to vary by less than 10‰. (iv) Results had to be reproducible on another day with a different sample scheme. Once this reproducibility had been established, variabilities in the δ2H values of organohalogen standards were investigated using the technique. The highest δ2H value of +75‰ was found for o,p´-DDD, whereas the strongest depletion in deuterium was found for Melipax (–181‰). The most important results for comparable compounds were as follows. DDT-related compounds gave δ2H values of between +59 and +75‰ (technical DDT, o,p´- and p,p´-DDD) or in the range of approximately −1‰, indicative of the different sources/methods of producing this compound. Four HCH isomers from the same supplier showed relatively similar hydrogen isotope distributions, whereas two lindane (γ–HCH) standards from other sources had 39‰ less deuterium. This difference is likely due to different purification steps during the isolation of pure lindane from the technical HCH mixture. An even greater difference was observed between the δ2H values of Toxaphene (US product dating from 1978) and Melipax (product from the former East Germany, dating from 1979), which gave δ2H values of –101‰ and –181‰, respectively, meaning that both products were easily distinguished via δ2H-IRMS. Fractioning of hydrogen isotopes in the atmospheric water cycle was suggested as one reason for the different values. In this theory, the water (which had different δ2H values depending on where it was taken from) was incorporated during the biosynthesis of camphene, which is the natural product used to produce both products. These results indicate that hydrogen isotope-specific analysis can be a valuable tool for tracing the origins of a compound in certain cases.
Keywords: Stable hydrogen isotope ratios; EA-IRMS; δ2H; Chromium reactor; Polyhalogenated compounds
Establishing a chromium-reactor design for measuring δ2H values of solid polyhalogenated compounds using direct elemental analysis and stable isotope ratio mass spectrometry by Wolfgang Armbruster; Katja Lehnert; Walter Vetter (pp. 237-243).
2H/1H isotope ratios of polyhalogenated compounds were determined by elemental analysis and isotope ratio mass spectrometry (EA-IRMS). Initial measurements with standard EA-IRMS equipment, which used high-temperature pyrolysis to convert the organic compounds into hydrogen, did not achieve significant signals for polychlorinated pesticides and related compounds, presumably due to the formation of HCl instead of hydrogen. To reverse this problematic reaction, a chromium reactor was incorporated into the element analyzer system, which scavenged Cl, forming chromium chloride and releasing hydrogen again in the form of H2. The optimized system therefore allowed the δ2H values of polyhalogenated compounds to be determined. A quality assurance program was developed based on several parameters. (i) Each compound was analyzed using a sequence of five injections, where the first measurement was discarded. (ii) Recovery of H (when calculated relative to acetanilide) had to be >90% for all replicates in a sequence. (iii) All δ-values within a sequence had to vary by less than 10‰. (iv) Results had to be reproducible on another day with a different sample scheme. Once this reproducibility had been established, variabilities in the δ2H values of organohalogen standards were investigated using the technique. The highest δ2H value of +75‰ was found for o,p´-DDD, whereas the strongest depletion in deuterium was found for Melipax (–181‰). The most important results for comparable compounds were as follows. DDT-related compounds gave δ2H values of between +59 and +75‰ (technical DDT, o,p´- and p,p´-DDD) or in the range of approximately −1‰, indicative of the different sources/methods of producing this compound. Four HCH isomers from the same supplier showed relatively similar hydrogen isotope distributions, whereas two lindane (γ–HCH) standards from other sources had 39‰ less deuterium. This difference is likely due to different purification steps during the isolation of pure lindane from the technical HCH mixture. An even greater difference was observed between the δ2H values of Toxaphene (US product dating from 1978) and Melipax (product from the former East Germany, dating from 1979), which gave δ2H values of –101‰ and –181‰, respectively, meaning that both products were easily distinguished via δ2H-IRMS. Fractioning of hydrogen isotopes in the atmospheric water cycle was suggested as one reason for the different values. In this theory, the water (which had different δ2H values depending on where it was taken from) was incorporated during the biosynthesis of camphene, which is the natural product used to produce both products. These results indicate that hydrogen isotope-specific analysis can be a valuable tool for tracing the origins of a compound in certain cases.
Keywords: Stable hydrogen isotope ratios; EA-IRMS; δ2H; Chromium reactor; Polyhalogenated compounds
Enhancement of enzymatic digestion of Antarctic krill and successive extraction of selenium organic compounds by ultrasound treatment by Mariana Siwek; Amir Bari Noubar; Jan Bergmann; Bernd Niemeyer; Boris Galunsky (pp. 244-249).
In a previous work we described the isolation of selenium organic species from Antarctic krill after enzymatic hydrolysis. In this paper we present the results of the influence of ultrasonication on the enzymatic treatment and the successive isolation of selenomethionine. We showed that ultrasound-assisted enzymatic digestion leads to quantitative release of selenium in the soluble fraction and recovery of selenomethionine from the krill protein within a time 2 orders of magnitude shorter. The solubilised sample was analysed by size-exclusion chromatography and the selenomethionine content was quantified by high-performance liquid chromatography–inductively coupled plasma mass spectrometry. In total, 99% of the selenomethionine in the krill hydrolysate was recovered from the chromatographic fractions. It corresponds to 35% of the total selenium content in Antarctic krill. Monitoring by microscopy of the changes in the structure of the krill samples during ultrasonication suggested that the enhancement of the ultrasound-assisted enzymatic reaction was mainly due to decrease of mass transfer limitations. A reference experiment for ultrasound-assisted enzymatic digestion of cell-free protein in a homogeneous system does not exclude direct influence of the ultrasound energy on the enzyme–substrate interaction.
Keywords: Enzymatic digestion; High-performance liquid chromatography–inductively coupled plasma mass spectrometry; Krill; Selenium organic compounds; Ultrasonication
Enhancement of enzymatic digestion of Antarctic krill and successive extraction of selenium organic compounds by ultrasound treatment by Mariana Siwek; Amir Bari Noubar; Jan Bergmann; Bernd Niemeyer; Boris Galunsky (pp. 244-249).
In a previous work we described the isolation of selenium organic species from Antarctic krill after enzymatic hydrolysis. In this paper we present the results of the influence of ultrasonication on the enzymatic treatment and the successive isolation of selenomethionine. We showed that ultrasound-assisted enzymatic digestion leads to quantitative release of selenium in the soluble fraction and recovery of selenomethionine from the krill protein within a time 2 orders of magnitude shorter. The solubilised sample was analysed by size-exclusion chromatography and the selenomethionine content was quantified by high-performance liquid chromatography–inductively coupled plasma mass spectrometry. In total, 99% of the selenomethionine in the krill hydrolysate was recovered from the chromatographic fractions. It corresponds to 35% of the total selenium content in Antarctic krill. Monitoring by microscopy of the changes in the structure of the krill samples during ultrasonication suggested that the enhancement of the ultrasound-assisted enzymatic reaction was mainly due to decrease of mass transfer limitations. A reference experiment for ultrasound-assisted enzymatic digestion of cell-free protein in a homogeneous system does not exclude direct influence of the ultrasound energy on the enzyme–substrate interaction.
Keywords: Enzymatic digestion; High-performance liquid chromatography–inductively coupled plasma mass spectrometry; Krill; Selenium organic compounds; Ultrasonication
Capillary-channeled polymer (C-CP) fibers as a stationary phase in microbore high-performance liquid chromatography columns by Rayman D. Stanelle; Massimiliano Mignanelli; Phil Brown; R. Kenneth Marcus (pp. 250-258).
Microbore columns utilizing polypropylene capillary-channeled polymer (C-CP) fibers as the stationary phase in high-performance liquid chromatography (HPLC) have been investigated. The polypropylene C-CP fiber diameter is ∼50 μm, with eight channels along the periphery of the fiber ranging in diameter from ∼12 to 35 μm. The polypropylene C-CP fibers were packed into fluorinated ethylene propylene (FEP) tubing, 1.3 mm inner diameter, with lengths of 500, 750, and 1,000 mm, to examine the effects of increased column length with regards to plate height, resolution and analysis time. The low backpressures characteristic of the C-CP fiber stationary phases allow the length of the column to be increased without significantly decreasing the specific permeability. The high specific permeability (∼5×10−8 cm2) of the C-CP packed microbore columns yields a relatively low backpressure of 2.35 MPa at the highest flow rate of 17 μL/s (54 mm/s) for a 1,000 mm column. Radial compression of the soft-walled FEP tubing is accomplished by pulling the 1.7 mm o.d. column through a 1.4 mm diameter orifice. Reducing the inner diameter of the column from 1.3 to 1.0 mm lowered the interstitial fraction from 47% to 42%, decreased the A-term contributions to band broadening, resulted in a significant decrease in average plate height (∼30%), and increased resolution (∼36%) at identical linear velocities. Although the lower void volume of the radially compressed column increased the backpressure from 0.57 to 2.11 MPa at a linear velocity of ∼20 mm/s, the specific permeability only decreased from ∼7×10−8 to 4×10−8 cm2.
Keywords: Liquid chromatography; Capillary-channeled polymer; Fiber; Microbore; Radial compression
Capillary-channeled polymer (C-CP) fibers as a stationary phase in microbore high-performance liquid chromatography columns by Rayman D. Stanelle; Massimiliano Mignanelli; Phil Brown; R. Kenneth Marcus (pp. 250-258).
Microbore columns utilizing polypropylene capillary-channeled polymer (C-CP) fibers as the stationary phase in high-performance liquid chromatography (HPLC) have been investigated. The polypropylene C-CP fiber diameter is ∼50 μm, with eight channels along the periphery of the fiber ranging in diameter from ∼12 to 35 μm. The polypropylene C-CP fibers were packed into fluorinated ethylene propylene (FEP) tubing, 1.3 mm inner diameter, with lengths of 500, 750, and 1,000 mm, to examine the effects of increased column length with regards to plate height, resolution and analysis time. The low backpressures characteristic of the C-CP fiber stationary phases allow the length of the column to be increased without significantly decreasing the specific permeability. The high specific permeability (∼5×10−8 cm2) of the C-CP packed microbore columns yields a relatively low backpressure of 2.35 MPa at the highest flow rate of 17 μL/s (54 mm/s) for a 1,000 mm column. Radial compression of the soft-walled FEP tubing is accomplished by pulling the 1.7 mm o.d. column through a 1.4 mm diameter orifice. Reducing the inner diameter of the column from 1.3 to 1.0 mm lowered the interstitial fraction from 47% to 42%, decreased the A-term contributions to band broadening, resulted in a significant decrease in average plate height (∼30%), and increased resolution (∼36%) at identical linear velocities. Although the lower void volume of the radially compressed column increased the backpressure from 0.57 to 2.11 MPa at a linear velocity of ∼20 mm/s, the specific permeability only decreased from ∼7×10−8 to 4×10−8 cm2.
Keywords: Liquid chromatography; Capillary-channeled polymer; Fiber; Microbore; Radial compression
Analysis of alkyl polyglucosides in industrial products by capillary electrophoresis with pulsed amperometric detection by Jane Hübner; Anh Nguyen; Florin Turcu; David Melchior; Hans-Willi Kling; Siegmar Gäb; Oliver J. Schmitz (pp. 259-264).
Pulsed amperometric detection following micellar electrokinetic chromatography has been applied successfully to the direct detection of alkyl polyglucosides (APGs) in shampoos and other industrial products without prior conversion to highly absorbing or fluorescing derivatives. For electrochemical detection, it is necessary to dissociate the hydroxyl groups of the APGs. Thus, we used 0.1 M NaOH in the outlet vial to dissociate the APGs. The main problems associated with the combination of electrochemical detection and capillary electrophoresis are the need to isolate the detector from the electric field used in the capillary electrophoresis separation and the difficulty of aligning the working electrode with the end of the capillary. To overcome these problems, a simple capillary-electrode holder was constructed. This holder automatically aligns the capillary and the electrode in a wall-jet configuration without the aid of micropositioners and facilitates the replacement of electrodes and capillaries without reconstruction of the entire capillary/electrode setup. Special microcylindrical gold electrodes have been produced by sealing 300-μm-diameter gold wire into borosilicate-glass capillaries.
Keywords: Capillary electrophoresis; Alkyl polyglucosides; Electrochemical detection; Tensides; Pulsed amperometric detection
Analysis of alkyl polyglucosides in industrial products by capillary electrophoresis with pulsed amperometric detection by Jane Hübner; Anh Nguyen; Florin Turcu; David Melchior; Hans-Willi Kling; Siegmar Gäb; Oliver J. Schmitz (pp. 259-264).
Pulsed amperometric detection following micellar electrokinetic chromatography has been applied successfully to the direct detection of alkyl polyglucosides (APGs) in shampoos and other industrial products without prior conversion to highly absorbing or fluorescing derivatives. For electrochemical detection, it is necessary to dissociate the hydroxyl groups of the APGs. Thus, we used 0.1 M NaOH in the outlet vial to dissociate the APGs. The main problems associated with the combination of electrochemical detection and capillary electrophoresis are the need to isolate the detector from the electric field used in the capillary electrophoresis separation and the difficulty of aligning the working electrode with the end of the capillary. To overcome these problems, a simple capillary-electrode holder was constructed. This holder automatically aligns the capillary and the electrode in a wall-jet configuration without the aid of micropositioners and facilitates the replacement of electrodes and capillaries without reconstruction of the entire capillary/electrode setup. Special microcylindrical gold electrodes have been produced by sealing 300-μm-diameter gold wire into borosilicate-glass capillaries.
Keywords: Capillary electrophoresis; Alkyl polyglucosides; Electrochemical detection; Tensides; Pulsed amperometric detection
Rapid separation of strychnine and brucine on a dynamically modified poly(dimethylsiloxane) microchip followed by electrochemical detection by Q. L. Zhang; J. J. Xu; H. Z. Lian; X. Y. Li; H. Y. Chen (pp. 265-270).
A method has been developed for rapidly separating and detecting strychnine and brucine using a poly(dimethysiloxane) (PDMS) microchip and electrochemical (EC) detection. PDMS microchannels dynamically modified by Brij35 are shown to be more efficient than native ones. The two analytes are well separated within 90 s in 70 mmol/L acetate buffer (pH 5.5) containing 0.01% (v/v) Brij35. Detection limits were found to be 1.0 μmol/L for strychnine and 0.2 μmol/L for brucine at S/N=3. The method was used to determine trace strychnine and brucine in rat serum, and the results obtained correlate well with those obtained via high-performance liquid chromatography (HPLC).
Keywords: PDMS microchip; Electrochemical detection; Strychnine; Brucine; Carbon fiber microcolumn electrode
Rapid separation of strychnine and brucine on a dynamically modified poly(dimethylsiloxane) microchip followed by electrochemical detection by Q. L. Zhang; J. J. Xu; H. Z. Lian; X. Y. Li; H. Y. Chen (pp. 265-270).
A method has been developed for rapidly separating and detecting strychnine and brucine using a poly(dimethysiloxane) (PDMS) microchip and electrochemical (EC) detection. PDMS microchannels dynamically modified by Brij35 are shown to be more efficient than native ones. The two analytes are well separated within 90 s in 70 mmol/L acetate buffer (pH 5.5) containing 0.01% (v/v) Brij35. Detection limits were found to be 1.0 μmol/L for strychnine and 0.2 μmol/L for brucine at S/N=3. The method was used to determine trace strychnine and brucine in rat serum, and the results obtained correlate well with those obtained via high-performance liquid chromatography (HPLC).
Keywords: PDMS microchip; Electrochemical detection; Strychnine; Brucine; Carbon fiber microcolumn electrode
Studying variations in the PCDD/PCDF profile across various food products using multivariate statistical analysis by Jean-Philippe Antignac; Philippe Marchand; Christel Gade; Gilles Matayron; El Mostafa Qannari; Bruno Le Bizec; François Andre (pp. 271-279).
Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) are widely recognized by the scientific community as persistent organic pollutants due to their toxicity and adverse effects on wildlife and human health. The actual regulation dedicated to the monitoring of dioxins in food is based on the measurement of 17 congener concentrations. The final result is reported as a toxic equivalent value that takes into account the relative toxicity of each congener. This procedure can minimize the qualitative information available from the abundances of each PCDD/PCDF congener: the characteristic contamination profile of the sample. Multivariate statistical techniques, such as principal component analysis (PCA) or linear discriminant analysis (LDA), represent an interesting way to investigate this qualitative information. Nevertheless, they have only been applied to the analysis of contamination data from food products and biological matrices infrequently. The objective of the present study was to analyze a large data set from dioxin analyses performed on various food products of animal origin. The results demonstrate the existence of differences in congener-specific patterns between the analyzed samples. Variability was first demonstrated in terms of the food type (fish, meat, milk, fatty products). Then a variability was observed that was related to the specific animal species for meat and milk samples (bovine, ovine, porcine, caprine and poultry). Some practical applications of these results are discussed. The origin(s) of the observed differences, as well as their significance, now remain to be investigated, both in terms of environmental factors and transfer through living organisms. A better knowledge of the relation between a contamination profile and its specific source and/or food product should be of great interest to scientists working in the fields of contaminant analysis, toxicology and metabolism, as well as to regulatory bodies and risk assessors in charge of final decisions regarding the eventual hazards associated with theses substances.
Keywords: Dioxins; PCDD; PCDF; Contamination profile; Food
Studying variations in the PCDD/PCDF profile across various food products using multivariate statistical analysis by Jean-Philippe Antignac; Philippe Marchand; Christel Gade; Gilles Matayron; El Mostafa Qannari; Bruno Le Bizec; François Andre (pp. 271-279).
Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) are widely recognized by the scientific community as persistent organic pollutants due to their toxicity and adverse effects on wildlife and human health. The actual regulation dedicated to the monitoring of dioxins in food is based on the measurement of 17 congener concentrations. The final result is reported as a toxic equivalent value that takes into account the relative toxicity of each congener. This procedure can minimize the qualitative information available from the abundances of each PCDD/PCDF congener: the characteristic contamination profile of the sample. Multivariate statistical techniques, such as principal component analysis (PCA) or linear discriminant analysis (LDA), represent an interesting way to investigate this qualitative information. Nevertheless, they have only been applied to the analysis of contamination data from food products and biological matrices infrequently. The objective of the present study was to analyze a large data set from dioxin analyses performed on various food products of animal origin. The results demonstrate the existence of differences in congener-specific patterns between the analyzed samples. Variability was first demonstrated in terms of the food type (fish, meat, milk, fatty products). Then a variability was observed that was related to the specific animal species for meat and milk samples (bovine, ovine, porcine, caprine and poultry). Some practical applications of these results are discussed. The origin(s) of the observed differences, as well as their significance, now remain to be investigated, both in terms of environmental factors and transfer through living organisms. A better knowledge of the relation between a contamination profile and its specific source and/or food product should be of great interest to scientists working in the fields of contaminant analysis, toxicology and metabolism, as well as to regulatory bodies and risk assessors in charge of final decisions regarding the eventual hazards associated with theses substances.
Keywords: Dioxins; PCDD; PCDF; Contamination profile; Food
Automatic determination of phylloquinone in vegetables and fruits using on-line photochemical reduction and fluorescence detection via solid phase extraction and flow injection by Tomás Pérez-Ruiz; Carmen Martínez-Lozano; Jesús Martín; Maria Dolores García (pp. 280-285).
A very simple, rapid and highly sensitive flow injection fluorimetric method was developed for the determination of phylloquinone. The assay was based on the on-line reduction of phylloquinone in dodecylsulfate micelles after irradiation with UV light. The micellar medium enhanced the fluorescence and stability of the reduced phylloquinone. Under optimum experimental conditions, the range of application of the technique was between 0.09 and 45.0 μg mL−1 and the detection limit was 0.05 μg mL−1. The sample throughput was 90 injections per hour. The reliability of the method for the routine analysis of phylloquinone in vegetables and fruits is demonstrated. Extractions were made with hexane, and an automated solid phase extraction system was used to purify the sample extracts prior to injection into the flow injection manifold.
Keywords: Phylloquinone; On-line photoreduction; SDS micelles; Fluorescence; Flow injection; Vegetables; Fruits
Automatic determination of phylloquinone in vegetables and fruits using on-line photochemical reduction and fluorescence detection via solid phase extraction and flow injection by Tomás Pérez-Ruiz; Carmen Martínez-Lozano; Jesús Martín; Maria Dolores García (pp. 280-285).
A very simple, rapid and highly sensitive flow injection fluorimetric method was developed for the determination of phylloquinone. The assay was based on the on-line reduction of phylloquinone in dodecylsulfate micelles after irradiation with UV light. The micellar medium enhanced the fluorescence and stability of the reduced phylloquinone. Under optimum experimental conditions, the range of application of the technique was between 0.09 and 45.0 μg mL−1 and the detection limit was 0.05 μg mL−1. The sample throughput was 90 injections per hour. The reliability of the method for the routine analysis of phylloquinone in vegetables and fruits is demonstrated. Extractions were made with hexane, and an automated solid phase extraction system was used to purify the sample extracts prior to injection into the flow injection manifold.
Keywords: Phylloquinone; On-line photoreduction; SDS micelles; Fluorescence; Flow injection; Vegetables; Fruits
Direct competitive ELISA based on a monoclonal antibody for detection of aflatoxin B1. Stabilization of ELISA kit components and application to grain samples by Anna Yu Kolosova; Won-Bo Shim; Zheng-You Yang; Sergei A. Eremin; Duck-Hwa Chung (pp. 286-294).
A direct competitive enzyme-linked immunosorbent assay (ELISA) based on a monoclonal antibody has been developed and optimized for detection of aflatoxin B1 (AFB1), and an ELISA kit has been designed. This immunoassay was highly specific, sensitive, rapid, simple, and suitable for aflatoxin monitoring. AFB1 concentrations determinable by ELISA ranged from 0.1 to 10 μg L−1. The IC50 value was 0.62 μg L−1. Recovery from spiked rice samples averaged between 94 and 113%. The effect of different reagents on the stability of HRP–AFB1 conjugate solution was studied. The performance of a stabilized enzyme tracer in ELISA was determined and compared with that of a freshly prepared control solution of HRP–AFB1 conjugate. The results showed that stabilizing media containing 0.02% BSA, 0.1% Kathon CG, and 0.05 mol L−1 calcium chloride in 0.05 mol L−1 Tris-HCl buffer (pH 7.2) maintained the activity of HRP–AFB1 at a dilution of 1:1000 for a period of at least 12 months at room temperature whereas the reference conjugate solution without the additives lost its activity within a few days. Several additives were tested for their stabilizing effect on a monoclonal antibody (MAb) immobilized on the surface of polystyrene microtitre plates. It was shown that immobilized MAb, treated with post-coating solutions containing PVA, BSA, and combinations of these substances with trehalose, retained its activity for at least 4 months at 4°C, whereas the untreated MAb-coated plate lost its activity within 2 days.
Keywords: ELISA; Monoclonal antibodies; Aflatoxin B1 ; HRP conjugate; Stabilization
Direct competitive ELISA based on a monoclonal antibody for detection of aflatoxin B1. Stabilization of ELISA kit components and application to grain samples by Anna Yu Kolosova; Won-Bo Shim; Zheng-You Yang; Sergei A. Eremin; Duck-Hwa Chung (pp. 286-294).
A direct competitive enzyme-linked immunosorbent assay (ELISA) based on a monoclonal antibody has been developed and optimized for detection of aflatoxin B1 (AFB1), and an ELISA kit has been designed. This immunoassay was highly specific, sensitive, rapid, simple, and suitable for aflatoxin monitoring. AFB1 concentrations determinable by ELISA ranged from 0.1 to 10 μg L−1. The IC50 value was 0.62 μg L−1. Recovery from spiked rice samples averaged between 94 and 113%. The effect of different reagents on the stability of HRP–AFB1 conjugate solution was studied. The performance of a stabilized enzyme tracer in ELISA was determined and compared with that of a freshly prepared control solution of HRP–AFB1 conjugate. The results showed that stabilizing media containing 0.02% BSA, 0.1% Kathon CG, and 0.05 mol L−1 calcium chloride in 0.05 mol L−1 Tris-HCl buffer (pH 7.2) maintained the activity of HRP–AFB1 at a dilution of 1:1000 for a period of at least 12 months at room temperature whereas the reference conjugate solution without the additives lost its activity within a few days. Several additives were tested for their stabilizing effect on a monoclonal antibody (MAb) immobilized on the surface of polystyrene microtitre plates. It was shown that immobilized MAb, treated with post-coating solutions containing PVA, BSA, and combinations of these substances with trehalose, retained its activity for at least 4 months at 4°C, whereas the untreated MAb-coated plate lost its activity within 2 days.
Keywords: ELISA; Monoclonal antibodies; Aflatoxin B1 ; HRP conjugate; Stabilization
Establishment of signal-recovery functions for calculation of recovery factor. Application to monitoring of contaminant residues in vegetables by chemiluminescence detection by Laura Gámiz-Gracia; Luis Cuadros-Rodríguez; Jorge J. Soto-Chinchilla; José F. Huertas-Pérez; Antonio González-Casado; Ana M. García-Campaña (pp. 295-301).
A new strategy is proposed for verifying if recovery factor is constant and independent of the real analyte content of samples. A signal-recovery function has been developed on the basis of measurement of spiked test samples before and after a pre-treatment step and considering, as starting point, a recent IUPAC recommendation which distinguishes between two terms—recovery factor, R, and apparent recovery, R*. Apparent recovery includes recovery factor and a new recovery term proposed in a previous paper by the authors, named calibration recovery, R C. The signal-recovery function is obtained directly from the measured analytical signals instead of from the concentrations, simplifying the calculations. A linear signal-recovery curve indicates that the recovery factor is constant in the analyte concentration range studied experimentally and, in this way, a single recovery factor can be calculated. The usefulness of the proposed method has been shown by quantification of the pesticide carbaryl by two different flow-injection analysis methods with chemiluminescent detection based on the luminol and TCPO systems. Good results were obtained from both methods.
Keywords: Recovery factor; Signal-recovery function; Chemiluminescence; Flow-injection analysis
Establishment of signal-recovery functions for calculation of recovery factor. Application to monitoring of contaminant residues in vegetables by chemiluminescence detection by Laura Gámiz-Gracia; Luis Cuadros-Rodríguez; Jorge J. Soto-Chinchilla; José F. Huertas-Pérez; Antonio González-Casado; Ana M. García-Campaña (pp. 295-301).
A new strategy is proposed for verifying if recovery factor is constant and independent of the real analyte content of samples. A signal-recovery function has been developed on the basis of measurement of spiked test samples before and after a pre-treatment step and considering, as starting point, a recent IUPAC recommendation which distinguishes between two terms—recovery factor, R, and apparent recovery, R*. Apparent recovery includes recovery factor and a new recovery term proposed in a previous paper by the authors, named calibration recovery, R C. The signal-recovery function is obtained directly from the measured analytical signals instead of from the concentrations, simplifying the calculations. A linear signal-recovery curve indicates that the recovery factor is constant in the analyte concentration range studied experimentally and, in this way, a single recovery factor can be calculated. The usefulness of the proposed method has been shown by quantification of the pesticide carbaryl by two different flow-injection analysis methods with chemiluminescent detection based on the luminol and TCPO systems. Good results were obtained from both methods.
Keywords: Recovery factor; Signal-recovery function; Chemiluminescence; Flow-injection analysis
Vibrational and microbiological study on alkaline metal picolinates and o-iodobenzoates by P. Koczoń; J. Piekut; M. Borawska; R. Świsłocka; W. Lewandowski (pp. 302-308).
FT–IR and Raman experimental data were assigned to appropriate bond vibrations and used to compare the different electronic charge distributions in the aromatic rings and carboxylic anions of various lithium, sodium, potassium, rubidium and caesium o-iodobenzoates and picolinates. Then principal component analysis (PCA) was applied in order to attempt to distinguish the biological activities of these compounds according to selected band wavenumbers. The growth of the bacteria Escherichia coli and Bacillus subtilis and the yeasts Saccharomyces cerevisiae and Hansenula anomala under optimal growth conditions were measured after 24 hours of incubation by the classical plate method. The influence of the picolinates and o-iodobenzoates on the growth of these microorganisms, again after 24 hours of incubation, was also measured and compared to the effect of sodium benzoate, which was used as a reference material. In general, the o-iodobenzoates exhibited more activity against the microorganisms than the picolinates. A statistically significant linear correlation between the spectral data and the degree of influence of a given compound on microorganism growth was established. The correlation coefficients for the o-iodobenzoates were 0.696, –0.628, 0.693 and 0.755 for E. coli, B. subtilis, H. anomala and S. cerevisiae, respectively, and for the picolinates they were 0.818, 0.826, 0.821 and 0.877 for E. coli, B. subtilis, H. anomala and S. cerevisiae, respectively. Therefore, IR spectroscopy is shown to be a rapid and reliable analytical tool for preliminary estimation of the antimicrobial properties of newly synthesized compounds, that can be applied before microbial performance tests.
Keywords: IR; Benzoic acid derivatives; Antimicrobial activity; Food preservatives
Vibrational and microbiological study on alkaline metal picolinates and o-iodobenzoates by P. Koczoń; J. Piekut; M. Borawska; R. Świsłocka; W. Lewandowski (pp. 302-308).
FT–IR and Raman experimental data were assigned to appropriate bond vibrations and used to compare the different electronic charge distributions in the aromatic rings and carboxylic anions of various lithium, sodium, potassium, rubidium and caesium o-iodobenzoates and picolinates. Then principal component analysis (PCA) was applied in order to attempt to distinguish the biological activities of these compounds according to selected band wavenumbers. The growth of the bacteria Escherichia coli and Bacillus subtilis and the yeasts Saccharomyces cerevisiae and Hansenula anomala under optimal growth conditions were measured after 24 hours of incubation by the classical plate method. The influence of the picolinates and o-iodobenzoates on the growth of these microorganisms, again after 24 hours of incubation, was also measured and compared to the effect of sodium benzoate, which was used as a reference material. In general, the o-iodobenzoates exhibited more activity against the microorganisms than the picolinates. A statistically significant linear correlation between the spectral data and the degree of influence of a given compound on microorganism growth was established. The correlation coefficients for the o-iodobenzoates were 0.696, –0.628, 0.693 and 0.755 for E. coli, B. subtilis, H. anomala and S. cerevisiae, respectively, and for the picolinates they were 0.818, 0.826, 0.821 and 0.877 for E. coli, B. subtilis, H. anomala and S. cerevisiae, respectively. Therefore, IR spectroscopy is shown to be a rapid and reliable analytical tool for preliminary estimation of the antimicrobial properties of newly synthesized compounds, that can be applied before microbial performance tests.
Keywords: IR; Benzoic acid derivatives; Antimicrobial activity; Food preservatives