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Analytica Chimica Acta (v.556, #1)
Recent advances in analytical chemistry—A material approach by Lin He; Chee-Seng Toh (pp. 1-15).
Advancements of materials research have profound direct impacts on developments in analytical chemistry and may hold the key to improvement of existing or new techniques at present times and near future. Applications of materials in analytical chemistry are reviewed, with focus on sensors, separations and extraction techniques. This review aims to survey examples of interesting works carried out in the last five years over a broad spectrum of materials classified as hybrids, nanomaterials and biomolecular materials.
Keywords: Hybrid materials; Nanomaterials; Biomolecules; Review; Analytical chemistry; Techniques
Recent advances in analytical chemistry—A material approach by Lin He; Chee-Seng Toh (pp. 1-15).
Advancements of materials research have profound direct impacts on developments in analytical chemistry and may hold the key to improvement of existing or new techniques at present times and near future. Applications of materials in analytical chemistry are reviewed, with focus on sensors, separations and extraction techniques. This review aims to survey examples of interesting works carried out in the last five years over a broad spectrum of materials classified as hybrids, nanomaterials and biomolecular materials.
Keywords: Hybrid materials; Nanomaterials; Biomolecules; Review; Analytical chemistry; Techniques
Recent analytical methodologies on equilibrium, kinetics, and dynamics at liquid/liquid interface by Satoshi Tsukahara (pp. 16-25).
The form of liquid/liquid interface is flexible and it cannot be fixed at a spatial position. Also the interface is prevented from any physical contact by the organic phase and aqueous phase. In addition, analytical methods operated in vacuo cannot be applied. These restrictions depressed the development of liquid/liquid interfacial chemistry. However, the modification of liquid/liquid interfacial form and original analytical methods have been invented interdependently. The present review classifies the forms of liquid/liquid interface first, and it arrays the related analytical methods with brief explanations. It dominantly deals with recent reports of analytical methodologies, which were published in 2001–2004, on equilibrium, kinetics, and dynamics of substances at liquid/liquid interface, but it also includes historically important studies.
Keywords: Liquid/liquid interface; Analytical methodology; Spectroscopy; Equilibrium; Kinetics; Dynamics
Recent analytical methodologies on equilibrium, kinetics, and dynamics at liquid/liquid interface by Satoshi Tsukahara (pp. 16-25).
The form of liquid/liquid interface is flexible and it cannot be fixed at a spatial position. Also the interface is prevented from any physical contact by the organic phase and aqueous phase. In addition, analytical methods operated in vacuo cannot be applied. These restrictions depressed the development of liquid/liquid interfacial chemistry. However, the modification of liquid/liquid interfacial form and original analytical methods have been invented interdependently. The present review classifies the forms of liquid/liquid interface first, and it arrays the related analytical methods with brief explanations. It dominantly deals with recent reports of analytical methodologies, which were published in 2001–2004, on equilibrium, kinetics, and dynamics of substances at liquid/liquid interface, but it also includes historically important studies.
Keywords: Liquid/liquid interface; Analytical methodology; Spectroscopy; Equilibrium; Kinetics; Dynamics
DNA-based bioanalytical microsystems for handheld device applications by Thomas Ming-Hung Lee; I-Ming Hsing (pp. 26-37).
This article reviews and highlights the current development of DNA-based bioanalytical microsystems for point-of-care diagnostics and on-site monitoring of food and water. Recent progresses in the miniaturization of various biological processing steps for the sample preparation, DNA amplification (polymerase chain reaction), and product detection are delineated in detail. Product detection approaches utilizing “portable? detection signals and electrochemistry-based methods are emphasized in this work. The strategies and challenges for the integration of individual processing module on the same chip are discussed.
Keywords: DNA; Bioanalytical microsystem; Lab-on-a-chip; Sample preparation; DNA amplification; Electrochemical detection
DNA-based bioanalytical microsystems for handheld device applications by Thomas Ming-Hung Lee; I-Ming Hsing (pp. 26-37).
This article reviews and highlights the current development of DNA-based bioanalytical microsystems for point-of-care diagnostics and on-site monitoring of food and water. Recent progresses in the miniaturization of various biological processing steps for the sample preparation, DNA amplification (polymerase chain reaction), and product detection are delineated in detail. Product detection approaches utilizing “portable” detection signals and electrochemistry-based methods are emphasized in this work. The strategies and challenges for the integration of individual processing module on the same chip are discussed.
Keywords: DNA; Bioanalytical microsystem; Lab-on-a-chip; Sample preparation; DNA amplification; Electrochemical detection
Analytical applications of room-temperature ionic liquids: A review of recent efforts by Siddharth Pandey (pp. 38-45).
Room-temperature ionic liquids (RTILs) are solvents that may have great potential in chemical analysis. Recent surge in the number of publications/reports/books/monographs clearly indicate an increasing interest of scientific and engineering community toward these exciting and unique solvents. Consequently, a variety of analytical applications of RTILs have started to emerge. This review presents an account of some of the recent reports on RTILs in major subdisciplines of analytical chemistry. Specifically, recent literature representing the applications of RTILs in chromatography, extraction, electroanalytical chemistry, sensing, and spectrometry is reviewed. With a rapid growth in the number of publications on analytical applications of RTILs, it appears that in the near future these neoteric solvents are definitely going to be a permanent feature in analytical chemistry.
Keywords: RTIL; Volatile organic solvents; Chromatography; Spectrometry
Analytical applications of room-temperature ionic liquids: A review of recent efforts by Siddharth Pandey (pp. 38-45).
Room-temperature ionic liquids (RTILs) are solvents that may have great potential in chemical analysis. Recent surge in the number of publications/reports/books/monographs clearly indicate an increasing interest of scientific and engineering community toward these exciting and unique solvents. Consequently, a variety of analytical applications of RTILs have started to emerge. This review presents an account of some of the recent reports on RTILs in major subdisciplines of analytical chemistry. Specifically, recent literature representing the applications of RTILs in chromatography, extraction, electroanalytical chemistry, sensing, and spectrometry is reviewed. With a rapid growth in the number of publications on analytical applications of RTILs, it appears that in the near future these neoteric solvents are definitely going to be a permanent feature in analytical chemistry.
Keywords: RTIL; Volatile organic solvents; Chromatography; Spectrometry
Electrochemical non-enzymatic glucose sensors by Sejin Park; Hankil Boo; Taek Dong Chung (pp. 46-57).
The electrochemical determination of glucose concentration without using enzyme is one of the dreams that many researchers have been trying to make come true. As new materials have been reported and more knowledge on detailed mechanism of glucose oxidation has been unveiled, the non-enzymatic glucose sensor keeps coming closer to practical applications. Recent reports strongly imply that this progress will be accelerated in ‘nanoera’. This article reviews the history of unraveling the mechanism of direct electrochemical oxidation of glucose and making attempts to develop successful electrochemical glucose sensors. The electrochemical oxidation of glucose molecules involves complex processes of adsorption, electron transfer, and subsequent chemical rearrangement, which are combined with the surface reactions on the metal surfaces. The information about the direct oxidation of glucose on solid-state surfaces as well as new electrode materials will lead us to possible breakthroughs in designing the enzymeless glucose sensing devices that realize innovative and powerful detection. An example of those is to introduce nanoporous platinum as an electrode, on which glucose is oxidized electrochemically with remarkable sensitivity and selectivity. Better model of such glucose sensors is sought by summarizing and revisiting the previous reports on the electrochemistry of glucose itself and new electrode materials.
Keywords: Non-enzymatic; Glucose sensor; Nanoporous; Glucose oxidation; Electrochemical sensor
Electrochemical non-enzymatic glucose sensors by Sejin Park; Hankil Boo; Taek Dong Chung (pp. 46-57).
The electrochemical determination of glucose concentration without using enzyme is one of the dreams that many researchers have been trying to make come true. As new materials have been reported and more knowledge on detailed mechanism of glucose oxidation has been unveiled, the non-enzymatic glucose sensor keeps coming closer to practical applications. Recent reports strongly imply that this progress will be accelerated in ‘nanoera’. This article reviews the history of unraveling the mechanism of direct electrochemical oxidation of glucose and making attempts to develop successful electrochemical glucose sensors. The electrochemical oxidation of glucose molecules involves complex processes of adsorption, electron transfer, and subsequent chemical rearrangement, which are combined with the surface reactions on the metal surfaces. The information about the direct oxidation of glucose on solid-state surfaces as well as new electrode materials will lead us to possible breakthroughs in designing the enzymeless glucose sensing devices that realize innovative and powerful detection. An example of those is to introduce nanoporous platinum as an electrode, on which glucose is oxidized electrochemically with remarkable sensitivity and selectivity. Better model of such glucose sensors is sought by summarizing and revisiting the previous reports on the electrochemistry of glucose itself and new electrode materials.
Keywords: Non-enzymatic; Glucose sensor; Nanoporous; Glucose oxidation; Electrochemical sensor
Designing split reporter proteins for analytical tools by Takeaki Ozawa (pp. 58-68).
A current focus of biological research is to quantify and image cellular processes in living cells and animals. To detect such cellular processes, genetically-encoded reporters have been extensively used. The most common reporters include firefly luciferase, renilla luciferase, green fluorescent protein (GFP) and its variants with various spectral properties. This review describes novel design of split-GFP and luciferase reporters based on protein splicing, and highlights some potential applications with the reporters to study protein–protein interactions, protein localization, intracellular protein dynamics, and protein activity in living cells and animals.
Keywords: Green fluorescent protein; Luciferase; Protein splicing; Protein–protein interaction
Designing split reporter proteins for analytical tools by Takeaki Ozawa (pp. 58-68).
A current focus of biological research is to quantify and image cellular processes in living cells and animals. To detect such cellular processes, genetically-encoded reporters have been extensively used. The most common reporters include firefly luciferase, renilla luciferase, green fluorescent protein (GFP) and its variants with various spectral properties. This review describes novel design of split-GFP and luciferase reporters based on protein splicing, and highlights some potential applications with the reporters to study protein–protein interactions, protein localization, intracellular protein dynamics, and protein activity in living cells and animals.
Keywords: Green fluorescent protein; Luciferase; Protein splicing; Protein–protein interaction
Advanced analytical tools in proteomics by Resmi C. Panicker; Souvik Chattopadhaya; Shao Q. Yao (pp. 69-79).
Proteomics deals with the study of proteins, their structures, localizations, posttranslational modifications, functions and interactions with other proteins. The mapping of protein structure–function holds the key to a better understanding of cellular functions under both normal and disease states, which is critical for modern drug discovery. However, the study of human proteome presents scientists with a task much more daunting than the human genome project. In fact, the estimated >100,000 different proteins expressed from 30,000 to 40,000 human genes make it extremely challenging, if not impossible with existing protein analysis techniques, to map the entire cellular functions at the translational level. Consequently, there have been rapid advances in the techniques and methods capable of large-scale proteomic studies. Among them, the recently developed high-throughput screening methods have enabled scientists to analyze proteins quickly and efficiently at an organism-wide scale. Herein, we overview some of these emerging tools for high-throughput protein analysis. In particular, we focus on recent advances in the bioassay development, which has provided sensitive and selective tools for high-throughput identification and characterizations of enzymes. Finally, the recently developed bioimaging techniques to visualize and quantify proteins in living cells are also discussed.
Keywords: Microarray; Peptide; Protein; Enzyme; Proteomics; 2D gel electrophoresis; Protein labeling; Bioimaging
Advanced analytical tools in proteomics by Resmi C. Panicker; Souvik Chattopadhaya; Shao Q. Yao (pp. 69-79).
Proteomics deals with the study of proteins, their structures, localizations, posttranslational modifications, functions and interactions with other proteins. The mapping of protein structure–function holds the key to a better understanding of cellular functions under both normal and disease states, which is critical for modern drug discovery. However, the study of human proteome presents scientists with a task much more daunting than the human genome project. In fact, the estimated >100,000 different proteins expressed from 30,000 to 40,000 human genes make it extremely challenging, if not impossible with existing protein analysis techniques, to map the entire cellular functions at the translational level. Consequently, there have been rapid advances in the techniques and methods capable of large-scale proteomic studies. Among them, the recently developed high-throughput screening methods have enabled scientists to analyze proteins quickly and efficiently at an organism-wide scale. Herein, we overview some of these emerging tools for high-throughput protein analysis. In particular, we focus on recent advances in the bioassay development, which has provided sensitive and selective tools for high-throughput identification and characterizations of enzymes. Finally, the recently developed bioimaging techniques to visualize and quantify proteins in living cells are also discussed.
Keywords: Microarray; Peptide; Protein; Enzyme; Proteomics; 2D gel electrophoresis; Protein labeling; Bioimaging
Polymeric microfluidic system for DNA analysis by Yi Sun; Yien C. Kwok (pp. 80-96).
The application of micro total analysis system (μTAS) has grown exponentially in the past decade. DNA analysis is one of the primary applications of μTAS technology. This review mainly focuses on the recent development of the polymeric microfluidic devices for DNA analysis. After a brief introduction of material characteristics of polymers, the various microfabrication methods are presented. The most recent developments and trends in the area of DNA analysis are then explored. We focus on the rapidly developing fields of cell sorting, cell lysis, DNA extraction and purification, polymerase chain reaction (PCR), DNA separation and detection. Lastly, commercially available polymer-based microdevices are included.
Keywords: Polymer; Microfabrication; DNA analysis; Microfluidic; Micro total analysis system
Polymeric microfluidic system for DNA analysis by Yi Sun; Yien C. Kwok (pp. 80-96).
The application of micro total analysis system (μTAS) has grown exponentially in the past decade. DNA analysis is one of the primary applications of μTAS technology. This review mainly focuses on the recent development of the polymeric microfluidic devices for DNA analysis. After a brief introduction of material characteristics of polymers, the various microfabrication methods are presented. The most recent developments and trends in the area of DNA analysis are then explored. We focus on the rapidly developing fields of cell sorting, cell lysis, DNA extraction and purification, polymerase chain reaction (PCR), DNA separation and detection. Lastly, commercially available polymer-based microdevices are included.
Keywords: Polymer; Microfabrication; DNA analysis; Microfluidic; Micro total analysis system
Separations based on the mechanical forces of light by Bum Suk Zhao; Yoon-Mo Koo; Doo Soo Chung (pp. 97-103).
A photon as a particle has an energy and a momentum. In a matter–photon interaction, the matter and photons may exchange their momenta observing the momentum conservation law. The consequence of the momentum transfer from a photon to a matter particle is a mechanical force exerted on the particle. Several separation methods based on this force of light are reviewed. Photophoresis separations for micron-sized particles and optical force chromatography for chemical-sized molecules are discussed.
Keywords: Photophoresis; Optical force chromatography; Molecule optics; Molecule prism
Separations based on the mechanical forces of light by Bum Suk Zhao; Yoon-Mo Koo; Doo Soo Chung (pp. 97-103).
A photon as a particle has an energy and a momentum. In a matter–photon interaction, the matter and photons may exchange their momenta observing the momentum conservation law. The consequence of the momentum transfer from a photon to a matter particle is a mechanical force exerted on the particle. Several separation methods based on this force of light are reviewed. Photophoresis separations for micron-sized particles and optical force chromatography for chemical-sized molecules are discussed.
Keywords: Photophoresis; Optical force chromatography; Molecule optics; Molecule prism
Separation of antidepressants by capillary electrophoresis with in-line solid-phase extraction using a novel monolithic adsorbent by David Schaller; Emily F. Hilder; Paul R. Haddad (pp. 104-111).
The separation of three selective serotonin reuptake inhibitors (SSRIs) by capillary electrophoresis (CE) with fully integrated solid-phase extraction (SPE) is described. Polymeric monolithic SPE modules were prepared in situ within a fused silica capillary from either butyl methacrylate- co-ethylene dimethacrylate or 3-sulfopropyl methacrylate- co-butyl methacrylate- co-ethylene dimethacrylate. Using a 1cm SPE module placed at the inlet of the capillary, a mixture of sertraline, fluoxetine and fluvoxamine was extracted from aqueous solution by applying a simple pressure rinse. Under pressure-driven conditions, efficient elution was possible from both SPE materials investigated using 50mM phosphate buffer, pH 3.5 in acetonitrile (20/80, v/v). Two different strategies were investigated for the efficient elution and subsequent CE separation. Injection of an aqueous sample plug directly into the non-aqueous elution/separation buffer was found to be unsuitable with poor elution profiles observed in the electrodriven mode. Alternatively, a sample plug equivalent to several capillary volumes could be injected by pressure followed by filling the capillary with the non-aqueous elution/separation buffer from the outlet end using a combination of pressure and electrodriven flow. Using a neutral monolith, efficient elution/separation was not possible due to an unstable electroosmotic flow (EOF), however, by adding the ionisable monomer, 3-sulfopropyl methacrylate to the SPE module to increase and stabilise the EOF, it was possible to achieve efficient elution from the SPE module, followed by baseline separation by CE using a 200mM acetate buffer, pH 3.5 in acetonitrile (10/90, v/v). With enrichment factors of over 500 achieved for each of the analytes this demonstrates the potential of in-line SPE-CE for the sensitive analysis of these drugs.
Keywords: Polymer monolith; In-line solid-phase extraction; Capillary electrophoresis; Drug analysis
Separation of antidepressants by capillary electrophoresis with in-line solid-phase extraction using a novel monolithic adsorbent by David Schaller; Emily F. Hilder; Paul R. Haddad (pp. 104-111).
The separation of three selective serotonin reuptake inhibitors (SSRIs) by capillary electrophoresis (CE) with fully integrated solid-phase extraction (SPE) is described. Polymeric monolithic SPE modules were prepared in situ within a fused silica capillary from either butyl methacrylate- co-ethylene dimethacrylate or 3-sulfopropyl methacrylate- co-butyl methacrylate- co-ethylene dimethacrylate. Using a 1cm SPE module placed at the inlet of the capillary, a mixture of sertraline, fluoxetine and fluvoxamine was extracted from aqueous solution by applying a simple pressure rinse. Under pressure-driven conditions, efficient elution was possible from both SPE materials investigated using 50mM phosphate buffer, pH 3.5 in acetonitrile (20/80, v/v). Two different strategies were investigated for the efficient elution and subsequent CE separation. Injection of an aqueous sample plug directly into the non-aqueous elution/separation buffer was found to be unsuitable with poor elution profiles observed in the electrodriven mode. Alternatively, a sample plug equivalent to several capillary volumes could be injected by pressure followed by filling the capillary with the non-aqueous elution/separation buffer from the outlet end using a combination of pressure and electrodriven flow. Using a neutral monolith, efficient elution/separation was not possible due to an unstable electroosmotic flow (EOF), however, by adding the ionisable monomer, 3-sulfopropyl methacrylate to the SPE module to increase and stabilise the EOF, it was possible to achieve efficient elution from the SPE module, followed by baseline separation by CE using a 200mM acetate buffer, pH 3.5 in acetonitrile (10/90, v/v). With enrichment factors of over 500 achieved for each of the analytes this demonstrates the potential of in-line SPE-CE for the sensitive analysis of these drugs.
Keywords: Polymer monolith; In-line solid-phase extraction; Capillary electrophoresis; Drug analysis
Measurement of ordered associate of protonated tetraphenylporphine formed at toluene/aqueous H2SO4 interface by attenuated total internal reflection spectroscopy with polarized light by Satoshi Tsukahara (pp. 112-120).
Attenuated total internal reflection (ATR) spectroscopy with an s- or p-polarized visible light was examined for some species of protonated 5,10,15,20-tetraphenylporphine (tpp) at toluene/aqueous H2SO4 (3–6moldm−3) interface. Tpp initially dissolved in the toluene phase was diprotonated at the interface to form monomeric H2tpp2+, the absorption peak of which was 438nm. At the same time, a long H2tpp2+ oligomer was formed, the absorption peak of which was 448nm. The two interfacial species were transient. Just after their disappearance, a rod-shaped H2tpp2+ associate was formed at the interface, the absorption peak of which was 417 and 478nm. The former and latter wavelengths corresponded to H- and J-bands of the associate, respectively. Theoretical calculation of the strength of electric field of light at the interface allowed one to estimate the interfacial concentration of the three species with measured reflection absorbance ( AR). The monomeric H2tpp2+ and its oligomer were at sub-monolayer levels, whereas the associate was at a multilayer level. Reflection absorption anisotropy ( KR), which was calculated from AR with the s- and p-polarized lights, was adopted for the evaluation of out-of-plane orientation of the interfacial species for the first time. The KR value suggested that the rod-shaped associate lay at the interface.
Keywords: Liquid/liquid interface; 5,10,15,20-Tetraphenylporphine associate; Reflection absorption anisotropy; Orientation; H- and J-aggregates; Attenuated total internal reflection spectroscopy with polarized lights
Measurement of ordered associate of protonated tetraphenylporphine formed at toluene/aqueous H2SO4 interface by attenuated total internal reflection spectroscopy with polarized light by Satoshi Tsukahara (pp. 112-120).
Attenuated total internal reflection (ATR) spectroscopy with an s- or p-polarized visible light was examined for some species of protonated 5,10,15,20-tetraphenylporphine (tpp) at toluene/aqueous H2SO4 (3–6moldm−3) interface. Tpp initially dissolved in the toluene phase was diprotonated at the interface to form monomeric H2tpp2+, the absorption peak of which was 438nm. At the same time, a long H2tpp2+ oligomer was formed, the absorption peak of which was 448nm. The two interfacial species were transient. Just after their disappearance, a rod-shaped H2tpp2+ associate was formed at the interface, the absorption peak of which was 417 and 478nm. The former and latter wavelengths corresponded to H- and J-bands of the associate, respectively. Theoretical calculation of the strength of electric field of light at the interface allowed one to estimate the interfacial concentration of the three species with measured reflection absorbance ( AR). The monomeric H2tpp2+ and its oligomer were at sub-monolayer levels, whereas the associate was at a multilayer level. Reflection absorption anisotropy ( KR), which was calculated from AR with the s- and p-polarized lights, was adopted for the evaluation of out-of-plane orientation of the interfacial species for the first time. The KR value suggested that the rod-shaped associate lay at the interface.
Keywords: Liquid/liquid interface; 5,10,15,20-Tetraphenylporphine associate; Reflection absorption anisotropy; Orientation; H- and J-aggregates; Attenuated total internal reflection spectroscopy with polarized lights
Preconcentration and frontal electroelution of amino acids for in-line solid-phase extraction–capillary electrophoresis by Michael C. Breadmore (pp. 121-126).
A new frontal electroelution approach that can be used for the preconcentration of amino acids in in-line solid-phase extraction–capillary electrophoresis (SPE–CE) has been developed. A single capillary was employed featuring a short monolithic SPE column created inside the capillary via photo-initiated, free-radical polymerisation of 3-sulfopropyl methacrylate and butyl methacrylate monomers. A weak electrolyte of dilute H2SO4, pH 2.9, was found to promote adsorption of the amino acids onto the SPE column. Elution of the amino acids was achieved using a dual solvation/ion-exchange transient boundary mobilised via EOF by using a strong electrolyte containing 62.5mM ethylenediamine, pH 2.9 with H2SO4 and 40% (v/v) acetonitrile. Using these two electrolytes, tryptophan was adsorbed onto the SPE column in weak electrolyte and eluted via a frontal electroelution mechanism in the strong electrolyte. Injections up to 20min, corresponding to over 14 column volumes (or 1400% of the capillary volume) of sample provided quantitative extraction of tryptophan from the weak electrolyte and were eluted without any loss in efficiency. This represents a practical increase of approximately 300-fold when compared to a typical hydrodynamic injection occupying 5% of the capillary volume.
Keywords: Solid-phase extraction; Capillary electrophoresis; In-line SPE–CE; Frontal electroelution; Focusing
Preconcentration and frontal electroelution of amino acids for in-line solid-phase extraction–capillary electrophoresis by Michael C. Breadmore (pp. 121-126).
A new frontal electroelution approach that can be used for the preconcentration of amino acids in in-line solid-phase extraction–capillary electrophoresis (SPE–CE) has been developed. A single capillary was employed featuring a short monolithic SPE column created inside the capillary via photo-initiated, free-radical polymerisation of 3-sulfopropyl methacrylate and butyl methacrylate monomers. A weak electrolyte of dilute H2SO4, pH 2.9, was found to promote adsorption of the amino acids onto the SPE column. Elution of the amino acids was achieved using a dual solvation/ion-exchange transient boundary mobilised via EOF by using a strong electrolyte containing 62.5mM ethylenediamine, pH 2.9 with H2SO4 and 40% (v/v) acetonitrile. Using these two electrolytes, tryptophan was adsorbed onto the SPE column in weak electrolyte and eluted via a frontal electroelution mechanism in the strong electrolyte. Injections up to 20min, corresponding to over 14 column volumes (or 1400% of the capillary volume) of sample provided quantitative extraction of tryptophan from the weak electrolyte and were eluted without any loss in efficiency. This represents a practical increase of approximately 300-fold when compared to a typical hydrodynamic injection occupying 5% of the capillary volume.
Keywords: Solid-phase extraction; Capillary electrophoresis; In-line SPE–CE; Frontal electroelution; Focusing
Development of liposomal immunosensor for the measurement of insulin with femtomole detection by Ja-an Annie Ho; Shi-Chin Zeng; Ming-Ray Huang; Hung-Yi Kuo (pp. 127-132).
The monitoring of insulin is of great relevance for the management of diabetes, the detection of pancreatic islet-cell malfunction, the definition of hypoglycemia, and the diagnosis of insulinoma. A liposomal immunosensing system for the determination of insulin was developed in this study. The insulin sensor was constructed by the immobilization of anti-insulin antibodies on the inner wall of the microcapillary immunoseparator. Liposomes tagged with anti-insulin and encapsulating a fluorescent dye were used as the detectable label. In the presence of insulin, sandwich immunocomplexes were formed between the immobilized antibodies in the column, the sample of insulin, and the antibody-tagged sulforhodamine B-dye-loaded liposomes. Signals generated by lysing the bound liposomes with 30mM n-octyl-β-d-glucopyranoside were measured by a fluorescence detector. The detected signal was directly proportional to the amount of insulin in the test sample. The liposomal immunosensing system successfully detected as low as 136attomole. MeOH (30%) was used for the regeneration of antibody-binding sites in the microcapillary after each measurement, which allowed the immunoseparator to be used for at least 70 repeated assays. The antibody activity in this proposed microcapillary immunoseparator could be well maintained for at least 1 week. The calibration curve for insulin in Tris-buffered saline had a linear dynamic range of 10pM–10nM, and the total assay time was less than 30min. The coefficient of variation for triplicate measurements was <5.00%, which indicated that well-reproducible results can be obtained by this newly developed method.
Keywords: Liposome; Insulin; Sandwich assay; Flow-injection analysis
Development of liposomal immunosensor for the measurement of insulin with femtomole detection by Ja-an Annie Ho; Shi-Chin Zeng; Ming-Ray Huang; Hung-Yi Kuo (pp. 127-132).
The monitoring of insulin is of great relevance for the management of diabetes, the detection of pancreatic islet-cell malfunction, the definition of hypoglycemia, and the diagnosis of insulinoma. A liposomal immunosensing system for the determination of insulin was developed in this study. The insulin sensor was constructed by the immobilization of anti-insulin antibodies on the inner wall of the microcapillary immunoseparator. Liposomes tagged with anti-insulin and encapsulating a fluorescent dye were used as the detectable label. In the presence of insulin, sandwich immunocomplexes were formed between the immobilized antibodies in the column, the sample of insulin, and the antibody-tagged sulforhodamine B-dye-loaded liposomes. Signals generated by lysing the bound liposomes with 30mM n-octyl-β-d-glucopyranoside were measured by a fluorescence detector. The detected signal was directly proportional to the amount of insulin in the test sample. The liposomal immunosensing system successfully detected as low as 136attomole. MeOH (30%) was used for the regeneration of antibody-binding sites in the microcapillary after each measurement, which allowed the immunoseparator to be used for at least 70 repeated assays. The antibody activity in this proposed microcapillary immunoseparator could be well maintained for at least 1 week. The calibration curve for insulin in Tris-buffered saline had a linear dynamic range of 10pM–10nM, and the total assay time was less than 30min. The coefficient of variation for triplicate measurements was <5.00%, which indicated that well-reproducible results can be obtained by this newly developed method.
Keywords: Liposome; Insulin; Sandwich assay; Flow-injection analysis
Use of vitamin B2 for fluorescence detection of thymidine-related single-nucleotide polymorphisms by Seiichi Nishizawa; N.B. Sankaran; Takehiro Seino; Ying-Yu Cui; Qing Dai; Chun-Yan Xu; Keitaro Yoshimoto; Norio Teramae (pp. 133-139).
In combination with abasic site (AP site)-containing DNAs, potential use of a biotic fluorescence compound, Vitamin B2 (riboflavin), is demonstrated for the fluorescence detection of the thymine (T)-related single-nucleotide polymorphisms. Our method is based on construction of the AP site in DNA duplexes, which allows small ligands to bind to target nucleotides accompanied by fluorescence signaling: an AP site-containing probe DNA is hybridized with a target DNA so as to place the AP site toward a target nucleobase, by which hydrophobic microenvironments are provided for ligands to recognize target nucleotides through stacking and hydrogen-bonding interactions. In 10mM sodium cacodylate buffer solutions (pH 7.0) containing 100mM NaCl and 1.0mM EDTA, Vitamin B2 is found to selectively bind to T ( K11=1.8×106M−1 at 5°C) over other nucleobases, and this is accompanied by significant quenching of its fluorescence. While the sensing functions depend on the flanking sequences to the AP site, Vitamin B2 is applicable to the detection of T/C (cytosine), T/G (guanine) and T/A (adenine) mutation sequences of the CYP2A6 gene, where the flanking nucleobases are guanines in both positions (–GXG–,X=AP site).
Keywords: Vitamin B; 2; Abasic site; Ligand; Hydrogen bond; Stacking; Fluorescence detection; Single-nucleotide polymorphism
Use of vitamin B2 for fluorescence detection of thymidine-related single-nucleotide polymorphisms by Seiichi Nishizawa; N.B. Sankaran; Takehiro Seino; Ying-Yu Cui; Qing Dai; Chun-Yan Xu; Keitaro Yoshimoto; Norio Teramae (pp. 133-139).
In combination with abasic site (AP site)-containing DNAs, potential use of a biotic fluorescence compound, Vitamin B2 (riboflavin), is demonstrated for the fluorescence detection of the thymine (T)-related single-nucleotide polymorphisms. Our method is based on construction of the AP site in DNA duplexes, which allows small ligands to bind to target nucleotides accompanied by fluorescence signaling: an AP site-containing probe DNA is hybridized with a target DNA so as to place the AP site toward a target nucleobase, by which hydrophobic microenvironments are provided for ligands to recognize target nucleotides through stacking and hydrogen-bonding interactions. In 10mM sodium cacodylate buffer solutions (pH 7.0) containing 100mM NaCl and 1.0mM EDTA, Vitamin B2 is found to selectively bind to T ( K11=1.8×106M−1 at 5°C) over other nucleobases, and this is accompanied by significant quenching of its fluorescence. While the sensing functions depend on the flanking sequences to the AP site, Vitamin B2 is applicable to the detection of T/C (cytosine), T/G (guanine) and T/A (adenine) mutation sequences of the CYP2A6 gene, where the flanking nucleobases are guanines in both positions (–GXG–,X=AP site).
Keywords: Vitamin B; 2; Abasic site; Ligand; Hydrogen bond; Stacking; Fluorescence detection; Single-nucleotide polymorphism
Enrichment of N-terminal sulfonated peptides by a water-soluble fullerene derivative and its applications to highly efficient proteomics by Yong Ho Lee; Joong-Won Shin; Seungwan Ryu; Sang-Won Lee; Chang Hoon Lee; Kwangyeol Lee (pp. 140-144).
Recent studies have shown that N-terminal sulfonation of tryptic peptides by various sulfonating molecules greatly improves their post-source decay processes (e.g., in matrix-assisted laser desorption ionization) or the gas phase fragmentation processes (e.g., in tandem mass spectrometer), enhancing the ability to identify their sequences de novo. In the present work, we have demonstrated that incorporation of water-soluble C60- N, N-dimethylpyrrolidinium iodide selectively precipitates the 4-sulfophenyl isothiocyanate-modified peptide (SPITC-GGYR, SPITC-ASHLGLAR) by forming a noncovalent ion pair to the SO3− group of the SPITC, and thereby the C60 derivative can be utilized to enrich the modified peptide. Electrospray ionization (ESI) mass analyses show that the cationic SPITC-GGYR and SPITC-ASHLGLAR species are well separated from unmodified peptides and the modified peptides are subsequently detached from the C60 derivative upon using an acidic solution.
Keywords: N-terminal sulfonation; Water-soluble fullerene derivative; Tandem mass spectrometry; Liquid chromatography; de novo peptide sequencing
Enrichment of N-terminal sulfonated peptides by a water-soluble fullerene derivative and its applications to highly efficient proteomics by Yong Ho Lee; Joong-Won Shin; Seungwan Ryu; Sang-Won Lee; Chang Hoon Lee; Kwangyeol Lee (pp. 140-144).
Recent studies have shown that N-terminal sulfonation of tryptic peptides by various sulfonating molecules greatly improves their post-source decay processes (e.g., in matrix-assisted laser desorption ionization) or the gas phase fragmentation processes (e.g., in tandem mass spectrometer), enhancing the ability to identify their sequences de novo. In the present work, we have demonstrated that incorporation of water-soluble C60- N, N-dimethylpyrrolidinium iodide selectively precipitates the 4-sulfophenyl isothiocyanate-modified peptide (SPITC-GGYR, SPITC-ASHLGLAR) by forming a noncovalent ion pair to the SO3− group of the SPITC, and thereby the C60 derivative can be utilized to enrich the modified peptide. Electrospray ionization (ESI) mass analyses show that the cationic SPITC-GGYR and SPITC-ASHLGLAR species are well separated from unmodified peptides and the modified peptides are subsequently detached from the C60 derivative upon using an acidic solution.
Keywords: N-terminal sulfonation; Water-soluble fullerene derivative; Tandem mass spectrometry; Liquid chromatography; de novo peptide sequencing
A highly stable and sensitive chemically modified screen-printed electrode for sulfide analysis by Dong-Mung Tsai; Annamalai Senthil Kumar; Jyh-Myng Zen (pp. 145-150).
We report here a highly stable and sensitive chemically modified screen-printed carbon electrode (CMSPE) for sulfide analysis. The CMSPE was prepared by first ion-exchanging ferricyanide into a Tosflex anion-exchange polymer and then sealing with a tetraethyl orthosilicate sol–gel layer. The sol–gel overlayer coating was crucial to stabilize the electron mediator (i.e., Fe(CN)63−) from leaching. The strong interaction between the oxy–hydroxy functional group of sol–gel and the hydrophilic sites of Tosflex makes the composite highly rigid to trap the ferricyanide mediator. An obvious electrocatalytic sulfide oxidation current signal at ∼0.20V versus Ag/AgCl in pH 7 phosphate buffer solution was observed at the CMSPE. A linear calibration plot over a wide range of 0.1μM to 1mM with a slope of 5.6nA/μM was obtained by flow injection analysis. The detection limit (S/N=3) was 8.9nM (i.e., 25.6ppt). Practical utility of the system was applied to the determination of sulfide trapped from cigarette smoke and sulfide content in hot spring water.
Keywords: Ferricyanide; Tosflex; Sol–gel; Screen-printed electrode; Sulfide
A highly stable and sensitive chemically modified screen-printed electrode for sulfide analysis by Dong-Mung Tsai; Annamalai Senthil Kumar; Jyh-Myng Zen (pp. 145-150).
We report here a highly stable and sensitive chemically modified screen-printed carbon electrode (CMSPE) for sulfide analysis. The CMSPE was prepared by first ion-exchanging ferricyanide into a Tosflex anion-exchange polymer and then sealing with a tetraethyl orthosilicate sol–gel layer. The sol–gel overlayer coating was crucial to stabilize the electron mediator (i.e., Fe(CN)63−) from leaching. The strong interaction between the oxy–hydroxy functional group of sol–gel and the hydrophilic sites of Tosflex makes the composite highly rigid to trap the ferricyanide mediator. An obvious electrocatalytic sulfide oxidation current signal at ∼0.20V versus Ag/AgCl in pH 7 phosphate buffer solution was observed at the CMSPE. A linear calibration plot over a wide range of 0.1μM to 1mM with a slope of 5.6nA/μM was obtained by flow injection analysis. The detection limit (S/N=3) was 8.9nM (i.e., 25.6ppt). Practical utility of the system was applied to the determination of sulfide trapped from cigarette smoke and sulfide content in hot spring water.
Keywords: Ferricyanide; Tosflex; Sol–gel; Screen-printed electrode; Sulfide
A microfluidic chip based liquid–liquid extraction system with microporous membrane by Zeng-Xuan Cai; Qun Fang; Heng-Wu Chen; Zhao-Lun Fang (pp. 151-156).
A robust and simple approach for microfabricated chip based liquid–liquid extraction was developed for on-chip sample pretreatment. The chip based extraction system was composed of two microfabricated glass plates with a microporous membrane sandwiched in between. A simple bonding approach using epoxy was used to achieve bonding and sealing of the L–L extraction chip. Gravity was employed to drive the aqueous and organic flows through separate channels in the extraction system, separated by the membrane. During extraction, the analyte in an aqueous sample stream was transferred through the membrane into the organic stream. The fluorescence intensity of the analyte extracted into the organic stream was monitored in situ by a laser induced fluorescence detection system. The performance of the system was demonstrated using an aqueous solution of butyl rhodamine B (BRB) and isobutanol as sample and extractant, respectively. The system proved to be an efficient means for achieving chip based microporous membrane liquid–liquid extraction. The precision of fluorescence measurements was 1.5% R.S.D. ( n=4). A linear response range of 1×10−7 to 1×10−4M BRB was obtained with a regression equation: I=8.00×106 C+4.91. An enrichment factor of ca. 3 was obtained with an extraction efficiency of 69%.
Keywords: Microfluidic chip; Microporous membrane; Liquid–liquid extraction
A microfluidic chip based liquid–liquid extraction system with microporous membrane by Zeng-Xuan Cai; Qun Fang; Heng-Wu Chen; Zhao-Lun Fang (pp. 151-156).
A robust and simple approach for microfabricated chip based liquid–liquid extraction was developed for on-chip sample pretreatment. The chip based extraction system was composed of two microfabricated glass plates with a microporous membrane sandwiched in between. A simple bonding approach using epoxy was used to achieve bonding and sealing of the L–L extraction chip. Gravity was employed to drive the aqueous and organic flows through separate channels in the extraction system, separated by the membrane. During extraction, the analyte in an aqueous sample stream was transferred through the membrane into the organic stream. The fluorescence intensity of the analyte extracted into the organic stream was monitored in situ by a laser induced fluorescence detection system. The performance of the system was demonstrated using an aqueous solution of butyl rhodamine B (BRB) and isobutanol as sample and extractant, respectively. The system proved to be an efficient means for achieving chip based microporous membrane liquid–liquid extraction. The precision of fluorescence measurements was 1.5% R.S.D. ( n=4). A linear response range of 1×10−7 to 1×10−4M BRB was obtained with a regression equation: I=8.00×106 C+4.91. An enrichment factor of ca. 3 was obtained with an extraction efficiency of 69%.
Keywords: Microfluidic chip; Microporous membrane; Liquid–liquid extraction
Extraction mechanisms of charged organic dye molecules into silica-surfactant nanochannels in a porous alumina membrane by Akira Yamaguchi; Jun Watanabe; Mekawy M. Mahmoud; Rise Fujiwara; Kotaro Morita; Tomohisa Yamashita; Yosuke Amino; Yong Chen; Logudurai Radhakrishnan; Norio Teramae (pp. 157-163).
Extraction mechanisms of charged organic dye molecules are examined for an assembly of silica-surfactant nanochannels with a channel diameter of 3.4nm, which is formed inside the pores of an anodic alumina membrane by a surfactant-template method. Experimental results confirm that the extraction mechanism depends on the sign of a charge of the dye molecules. The extraction of the cationic rhodamine 6G is predominantly caused by an ion-pair extraction process, whereas an anion-exchange process is mainly responsible for the extraction of the anionic sulforhodamine B. These extraction mechanisms are discussed by considering the microstructures of the silica-surfactant nanochannels.
Keywords: Silica-surfactant nanochannel; Alumina membrane; Extraction
Extraction mechanisms of charged organic dye molecules into silica-surfactant nanochannels in a porous alumina membrane by Akira Yamaguchi; Jun Watanabe; Mekawy M. Mahmoud; Rise Fujiwara; Kotaro Morita; Tomohisa Yamashita; Yosuke Amino; Yong Chen; Logudurai Radhakrishnan; Norio Teramae (pp. 157-163).
Extraction mechanisms of charged organic dye molecules are examined for an assembly of silica-surfactant nanochannels with a channel diameter of 3.4nm, which is formed inside the pores of an anodic alumina membrane by a surfactant-template method. Experimental results confirm that the extraction mechanism depends on the sign of a charge of the dye molecules. The extraction of the cationic rhodamine 6G is predominantly caused by an ion-pair extraction process, whereas an anion-exchange process is mainly responsible for the extraction of the anionic sulforhodamine B. These extraction mechanisms are discussed by considering the microstructures of the silica-surfactant nanochannels.
Keywords: Silica-surfactant nanochannel; Alumina membrane; Extraction
Integration of multiple-ion-sensing on a capillary-assembled microchip by Hideaki Hisamoto; Midori Yasuoka; Shigeru Terabe (pp. 164-170).
Multiple-ion-sensing functions are integrated on a capillary-assembled microchip (CAs-CHIP). Since the CAs-CHIPs are fabricated by embedding various chemically functionalized square capillaries onto a lattice PDMS channel plate having same channel dimensions as outer dimensions of square capillaries, integration of parallel multiple-ion-sensing is easily realized. Here, three ion-sensing capillaries are prepared and used for integrating these functions onto a single microchip. Ion-sensing square capillaries (sodium, potassium, calcium) are prepared by attaching ion-selective optode membranes to inner wall of capillaries, and are characterized in terms of response time, response range, and ion selectivity. Finally, fully characterized ion-sensing capillaries are embedded into PDMS channel plate in parallel to fabricate a multiple-ion-sensing chip. The CAs-CHIP-based strategy is promising for integrating multiple chemical sensing functions onto a single microchip.
Keywords: Ion-selective optode; Ion sensor; Microchip; Polydimethylsiloxane; Square capillary
Integration of multiple-ion-sensing on a capillary-assembled microchip by Hideaki Hisamoto; Midori Yasuoka; Shigeru Terabe (pp. 164-170).
Multiple-ion-sensing functions are integrated on a capillary-assembled microchip (CAs-CHIP). Since the CAs-CHIPs are fabricated by embedding various chemically functionalized square capillaries onto a lattice PDMS channel plate having same channel dimensions as outer dimensions of square capillaries, integration of parallel multiple-ion-sensing is easily realized. Here, three ion-sensing capillaries are prepared and used for integrating these functions onto a single microchip. Ion-sensing square capillaries (sodium, potassium, calcium) are prepared by attaching ion-selective optode membranes to inner wall of capillaries, and are characterized in terms of response time, response range, and ion selectivity. Finally, fully characterized ion-sensing capillaries are embedded into PDMS channel plate in parallel to fabricate a multiple-ion-sensing chip. The CAs-CHIP-based strategy is promising for integrating multiple chemical sensing functions onto a single microchip.
Keywords: Ion-selective optode; Ion sensor; Microchip; Polydimethylsiloxane; Square capillary
Microbial detection in microfluidic devices through dual staining of quantum dots-labeled immunoassay and RNA hybridization by Qing Zhang; Liang Zhu; Hanhua Feng; Simon Ang; Fook Siong Chau; Wen-Tso Liu (pp. 171-177).
This paper reported the development of a microfludic device for the rapid detection of viable and nonviable microbial cells through dual labeling by fluorescent in situ hybridization (FISH) and quantum dots (QDs)-labeled immunofluorescent assay (IFA). The coin sized device consists of a microchannel and filtering pillars (gap=1–2μm) and was demonstrated to effectively trap and concentrate microbial cells (i.e. Giardia lamblia). After sample injection, FISH probe solution and QDs-labeled antibody solution were sequentially pumped into the device to accelerate the fluorescent labeling reactions at optimized flow rates (i.e. 1 and 20μL/min, respectively). After 2min washing for each assay, the whole process could be finished within 30min, with minimum consumption of labeling reagents and superior fluorescent signal intensity. The choice of QDs 525 for IFA resulted in bright and stable fluorescent signal, with minimum interference with the Cy3 signal from FISH detection.
Keywords: Microfluidic device; FISH; Immunofluorescent assay; Quantum dots; Giardia lamblia
Microbial detection in microfluidic devices through dual staining of quantum dots-labeled immunoassay and RNA hybridization by Qing Zhang; Liang Zhu; Hanhua Feng; Simon Ang; Fook Siong Chau; Wen-Tso Liu (pp. 171-177).
This paper reported the development of a microfludic device for the rapid detection of viable and nonviable microbial cells through dual labeling by fluorescent in situ hybridization (FISH) and quantum dots (QDs)-labeled immunofluorescent assay (IFA). The coin sized device consists of a microchannel and filtering pillars (gap=1–2μm) and was demonstrated to effectively trap and concentrate microbial cells (i.e. Giardia lamblia). After sample injection, FISH probe solution and QDs-labeled antibody solution were sequentially pumped into the device to accelerate the fluorescent labeling reactions at optimized flow rates (i.e. 1 and 20μL/min, respectively). After 2min washing for each assay, the whole process could be finished within 30min, with minimum consumption of labeling reagents and superior fluorescent signal intensity. The choice of QDs 525 for IFA resulted in bright and stable fluorescent signal, with minimum interference with the Cy3 signal from FISH detection.
Keywords: Microfluidic device; FISH; Immunofluorescent assay; Quantum dots; Giardia lamblia
Hadamard transform capillary electrophoresis combined with laser-induced fluorometry using electrokinetic injection by Kazuki Hata; Takashi Kaneta; Totaro Imasaka (pp. 178-182).
Hadamard transform capillary electrophoresis (HTCE) based on electrokinetic injection allows laser-induced fluorescence detection using a small laser, namely the laser-diode-pumped YAG laser, as an excitation source. A small hole is fabricated at the center of a capillary by laser ablation; this hole functions as an inlet port for a sample solution. Therefore, the sample solution can be introduced electrophoretically into the capillary through the small hole. Multiple sample injection is accomplished by introducing a buffer solution from the end of the capillary and the sample solution through the hole. Both solutions are injected using two sets of high-voltage power supplies and migrate toward the opposite end of the capillary. A fluorescent analyte, rhodamine B, is successfully detected in the case of both single and multiple injection according to the Hadamard sequence code. By transforming the data encoded by the Hadamard matrix, the decoded data showed an increase in the signal-to-noise (S/N) ratio by a factor of 9.8. In the case of the sample containing two amino acids labeled with rhodamine B isothiocyanate (RBITC), although the concentration of every component including free RBITC is lower than the concentration limit of detection obtained by single injection, a substantial improvement in the sensitivity is achieved and all components are identified by the Hadamard transform technique.
Keywords: Capillary electrophoresis; Hadamard transformation; Amino acid; Laser-induced fluorometry; Sensitive detection; Injection device
Hadamard transform capillary electrophoresis combined with laser-induced fluorometry using electrokinetic injection by Kazuki Hata; Takashi Kaneta; Totaro Imasaka (pp. 178-182).
Hadamard transform capillary electrophoresis (HTCE) based on electrokinetic injection allows laser-induced fluorescence detection using a small laser, namely the laser-diode-pumped YAG laser, as an excitation source. A small hole is fabricated at the center of a capillary by laser ablation; this hole functions as an inlet port for a sample solution. Therefore, the sample solution can be introduced electrophoretically into the capillary through the small hole. Multiple sample injection is accomplished by introducing a buffer solution from the end of the capillary and the sample solution through the hole. Both solutions are injected using two sets of high-voltage power supplies and migrate toward the opposite end of the capillary. A fluorescent analyte, rhodamine B, is successfully detected in the case of both single and multiple injection according to the Hadamard sequence code. By transforming the data encoded by the Hadamard matrix, the decoded data showed an increase in the signal-to-noise (S/N) ratio by a factor of 9.8. In the case of the sample containing two amino acids labeled with rhodamine B isothiocyanate (RBITC), although the concentration of every component including free RBITC is lower than the concentration limit of detection obtained by single injection, a substantial improvement in the sensitivity is achieved and all components are identified by the Hadamard transform technique.
Keywords: Capillary electrophoresis; Hadamard transformation; Amino acid; Laser-induced fluorometry; Sensitive detection; Injection device
Characterization of interaction property of multicomponents in Chinese Herb with protein by microdialysis combined with HPLC by Ming Guo; Xingye Su; Liang Kong; Xin Li; Hanfa Zou (pp. 183-188).
Interaction of traditional Chinese Herb Rhizoma Chuanxiong and protein was studied by microdialysis coupled with high performance liquid chromatography. Compounds in Rhizoma Chuanxiong, such as ferulic acid, senkyunolide A and 3-butylphthalide, were identified by HPLC, HPLC–MS and UV–vis. Microdialysis recoveries and binding degrees of compounds in Rhizoma Chuanxiong with human serum albumin (HSA) and other human plasma protein were determined: recoveries of microdialysis sampling ranged from 36.7 to 98.4% with R.S.D. below 3.1%; while binding to HSA ranged from 0 to 91.5% (0.3mM HSA) and from 0 to 93.5% (0.6mM HSA), respectively. Compared with HSA, most of compounds bound to human blood serum more extensively and the results showed that binding of these compounds in Rhizoma Chuanxiong was influenced by pH. Two compounds were found to bind to HSA and human blood serum, their binding degrees were consistent with ferulic acid and 3-butylphthalide, the active compounds in Rhizoma Chuangxiong.
Keywords: Interaction; Traditional Chinese medicine; Protein; Microdialysis; HPLC
Characterization of interaction property of multicomponents in Chinese Herb with protein by microdialysis combined with HPLC by Ming Guo; Xingye Su; Liang Kong; Xin Li; Hanfa Zou (pp. 183-188).
Interaction of traditional Chinese Herb Rhizoma Chuanxiong and protein was studied by microdialysis coupled with high performance liquid chromatography. Compounds in Rhizoma Chuanxiong, such as ferulic acid, senkyunolide A and 3-butylphthalide, were identified by HPLC, HPLC–MS and UV–vis. Microdialysis recoveries and binding degrees of compounds in Rhizoma Chuanxiong with human serum albumin (HSA) and other human plasma protein were determined: recoveries of microdialysis sampling ranged from 36.7 to 98.4% with R.S.D. below 3.1%; while binding to HSA ranged from 0 to 91.5% (0.3mM HSA) and from 0 to 93.5% (0.6mM HSA), respectively. Compared with HSA, most of compounds bound to human blood serum more extensively and the results showed that binding of these compounds in Rhizoma Chuanxiong was influenced by pH. Two compounds were found to bind to HSA and human blood serum, their binding degrees were consistent with ferulic acid and 3-butylphthalide, the active compounds in Rhizoma Chuangxiong.
Keywords: Interaction; Traditional Chinese medicine; Protein; Microdialysis; HPLC
Silver-ion redox sensing based on colloid formation by gallate ester derivatives by Setsuko Yajima; Yoshie Iwane; Eisaku Nomura; Hisaji Taniguchi; Keiichi Kimura (pp. 189-194).
Plasmon absorption of silver colloid, which was formed by reduction of silver ion with compounds bearing gallate ester groups in ethanol, was observed by absorption spectroscopy. The time-dependent absorption of silver colloid was found, which shows that the silver colloid is unstable and easy to aggregate. It seemed that a calixarene derivative bearing two gallate ester groups was the most suitable for determining silver ion. In order to prevent the silver colloid aggregation, poly( N-vinylpyrrolidone) (PVP) was added into the solution at a constant time after the preparation of sample solutions. In the calibration graph, the absorbance increased with increasing silver ion concentration, especially in the concentration range of 2.00×10−6 to 1.00×10−5M. It is possible to determine silver ion concentrations using this method.
Keywords: Silver nanoparticle; Gallate ester group; Silver ion reduction; Plasmon absorption; Quantitative determination
Silver-ion redox sensing based on colloid formation by gallate ester derivatives by Setsuko Yajima; Yoshie Iwane; Eisaku Nomura; Hisaji Taniguchi; Keiichi Kimura (pp. 189-194).
Plasmon absorption of silver colloid, which was formed by reduction of silver ion with compounds bearing gallate ester groups in ethanol, was observed by absorption spectroscopy. The time-dependent absorption of silver colloid was found, which shows that the silver colloid is unstable and easy to aggregate. It seemed that a calixarene derivative bearing two gallate ester groups was the most suitable for determining silver ion. In order to prevent the silver colloid aggregation, poly( N-vinylpyrrolidone) (PVP) was added into the solution at a constant time after the preparation of sample solutions. In the calibration graph, the absorbance increased with increasing silver ion concentration, especially in the concentration range of 2.00×10−6 to 1.00×10−5M. It is possible to determine silver ion concentrations using this method.
Keywords: Silver nanoparticle; Gallate ester group; Silver ion reduction; Plasmon absorption; Quantitative determination
Determination of sulfite in beer samples using an amperometric fill and flow channel biosensor employing sulfite oxidase by Min Zhao; D. Brynn Hibbert; J. Justin Gooding (pp. 195-200).
A simple method is described to determine sulfite in beer samples using a fill and flow channel biosensor. A droplet of sample is placed into the inlet of a rectangular flow cell and begins to flow through the channel by capillarity. The flow is maintained and controlled by a porous outlet plug of defined porosity. In a rectangular flow cell, the sample solution flows through three consecutive zones: over a predictor electrode, an enzyme layer and a detector electrode. Together these three zones enable the differentiation between current due to sulfite and current due to other electroactive species in the sample. The predictor electrode is located upstream, and on the opposite channel wall to the enzyme layer and detector electrode, and is poised at the same potential (+0.65V versus Ag/AgCl) as the detector electrode. On this electrode, the current contribution from all species in the sample solution that are oxidized at that potential is determined. The enzyme layer contains sulfite oxidase, which, in the process of oxidizing sulfite, produces hydrogen peroxide, which itself is reduced by excess sulfite. The current at the downstream detector electrode is therefore different from that at the predictor electrode as a result of the enzyme reaction and the difference of the currents, corrected for the dimensions of the electrodes, is proportional to the concentration of sulfite. The method enables a straightforward correction of the interfering current at the detector electrode and a determination of the analyte concentration. The effect of interferences from ascorbic acid, ethanol, sorbic acid and tartaric acid in the detection of sulfite is efficiently removed. The concentration of sulfite in a sample of beer measured by the biosensor is equivalent to that measured using a reference method based on the AOAC-recommended Monier–Williams method.
Keywords: Sulfite; Beer samples; Fill and flow channel biosensor; Enzymatic analysis
Determination of sulfite in beer samples using an amperometric fill and flow channel biosensor employing sulfite oxidase by Min Zhao; D. Brynn Hibbert; J. Justin Gooding (pp. 195-200).
A simple method is described to determine sulfite in beer samples using a fill and flow channel biosensor. A droplet of sample is placed into the inlet of a rectangular flow cell and begins to flow through the channel by capillarity. The flow is maintained and controlled by a porous outlet plug of defined porosity. In a rectangular flow cell, the sample solution flows through three consecutive zones: over a predictor electrode, an enzyme layer and a detector electrode. Together these three zones enable the differentiation between current due to sulfite and current due to other electroactive species in the sample. The predictor electrode is located upstream, and on the opposite channel wall to the enzyme layer and detector electrode, and is poised at the same potential (+0.65V versus Ag/AgCl) as the detector electrode. On this electrode, the current contribution from all species in the sample solution that are oxidized at that potential is determined. The enzyme layer contains sulfite oxidase, which, in the process of oxidizing sulfite, produces hydrogen peroxide, which itself is reduced by excess sulfite. The current at the downstream detector electrode is therefore different from that at the predictor electrode as a result of the enzyme reaction and the difference of the currents, corrected for the dimensions of the electrodes, is proportional to the concentration of sulfite. The method enables a straightforward correction of the interfering current at the detector electrode and a determination of the analyte concentration. The effect of interferences from ascorbic acid, ethanol, sorbic acid and tartaric acid in the detection of sulfite is efficiently removed. The concentration of sulfite in a sample of beer measured by the biosensor is equivalent to that measured using a reference method based on the AOAC-recommended Monier–Williams method.
Keywords: Sulfite; Beer samples; Fill and flow channel biosensor; Enzymatic analysis
Parametric studies of matched filters to enhance the signal-to-noise ratios of LC–MS–MS peaks by Shau-Chun Wang; Shu-Min Chiang; Chih-Min Huang (pp. 201-207).
Chromatographic parameters of reference signals employed in matched filter methods have been studied using numerical experiments to improve the signal-to-noise (S/N) ratios of small liquid chromatography (LC) peaks obtained with electrospray tandem mass spectrometers (MS–MS). These parameters include the width, shape, and S/N ratios of chromatographic peaks used as the reference signal profiles. Our results show the effect of reference peak widths on improving the S/N ratio of chromatographic peaks; the influence of reference peak shapes is negligible. To verify simulation results, various reference signals, including analyte peaks of high concentration standards, internal standard peaks, and artificial Gaussian peaks of different widths, have been employed to enhance signal peaks on real liquid chromatography–tandem mass spectrometry (LC–MS–MS) chromatograms via matched filter methods. Our experimental results demonstrate that the S/N ratio enhancement of chromatographic peaks agree with the simulation predictions. These findings, therefore, suggest that regardless of peak shape, a well-smooth peak with a width close to that of the analyte peak is an adequate reference signal, when matched filter methods are used to improve LC–MS–MS chromatograms. Nevertheless, all methods processed LC–MS–MS peaks in this study do not achieve the ideal improvement ratios estimated with simulation results. We attribute this deficiency to spike-like noise, which have considerable low frequency components riding on LC–MS–MS chromatograms. Matched filtering, which works as a low-pass filter in the frequency domain, cannot effectively eliminate low frequency flicker noise contributed by these spikes. In addition, simple median filtering does not provide adequate improvement despite being able to smooth out most spikes in the chromatograms.
Keywords: Matched filter; Liquid chromatography; Tandem mass spectrometry; Spike noise; Median filter
Parametric studies of matched filters to enhance the signal-to-noise ratios of LC–MS–MS peaks by Shau-Chun Wang; Shu-Min Chiang; Chih-Min Huang (pp. 201-207).
Chromatographic parameters of reference signals employed in matched filter methods have been studied using numerical experiments to improve the signal-to-noise (S/N) ratios of small liquid chromatography (LC) peaks obtained with electrospray tandem mass spectrometers (MS–MS). These parameters include the width, shape, and S/N ratios of chromatographic peaks used as the reference signal profiles. Our results show the effect of reference peak widths on improving the S/N ratio of chromatographic peaks; the influence of reference peak shapes is negligible. To verify simulation results, various reference signals, including analyte peaks of high concentration standards, internal standard peaks, and artificial Gaussian peaks of different widths, have been employed to enhance signal peaks on real liquid chromatography–tandem mass spectrometry (LC–MS–MS) chromatograms via matched filter methods. Our experimental results demonstrate that the S/N ratio enhancement of chromatographic peaks agree with the simulation predictions. These findings, therefore, suggest that regardless of peak shape, a well-smooth peak with a width close to that of the analyte peak is an adequate reference signal, when matched filter methods are used to improve LC–MS–MS chromatograms. Nevertheless, all methods processed LC–MS–MS peaks in this study do not achieve the ideal improvement ratios estimated with simulation results. We attribute this deficiency to spike-like noise, which have considerable low frequency components riding on LC–MS–MS chromatograms. Matched filtering, which works as a low-pass filter in the frequency domain, cannot effectively eliminate low frequency flicker noise contributed by these spikes. In addition, simple median filtering does not provide adequate improvement despite being able to smooth out most spikes in the chromatograms.
Keywords: Matched filter; Liquid chromatography; Tandem mass spectrometry; Spike noise; Median filter
Simple and robust near-infrared spectroscopic monitoring of indium-tin-oxide (ITO) etching solution using Teflon tubing by Sanghee Nah; Kyungtag Ryu; Soohwa Cho; Hoeil Chung; Hankyu Namkung (pp. 208-215).
The ability to monitor etching solutions using a spectroscopy directly through existing Teflon lines in electronic industries is highly beneficial and offers many advantages. A monitoring method was developed using near-infrared (NIR) measurements with Teflon tubing as a sample container for the quantification of components in the indium-tin-oxide (ITO) etching solution composed of hydrochloric acid (HCl), acetic acid (CH3COOH) and water. Measurements were reproducible and it was possible to use the same calibration model for different Teflon tubings. Even though partial least squares (PLS) calibration performance was slightly degraded for Teflon cells when compared to quartz cells of the similar pathlength, the calibration data correlated well with reference data. The robustness of Teflon-based NIR measurement was evaluated by predicting the spectra of 10 independent samples that were collected using five different Teflon tubes. Although, two Teflon tubes were visually less transparent than the other three, there was no significant variation in the standard error of predictions (SEPs) among the five Teflon tubes. Calibration accuracy was successfully maintained and highly repeatable prediction results were achieved. This study verifies that a Teflon-based NIR measurement is reliable for the monitoring of etching solutions and it can be successfully integrated into on-line process monitoring.
Keywords: Near-infrared spectroscopy; Indium-tin-oxide (ITO) etching solution; Teflon
Simple and robust near-infrared spectroscopic monitoring of indium-tin-oxide (ITO) etching solution using Teflon tubing by Sanghee Nah; Kyungtag Ryu; Soohwa Cho; Hoeil Chung; Hankyu Namkung (pp. 208-215).
The ability to monitor etching solutions using a spectroscopy directly through existing Teflon lines in electronic industries is highly beneficial and offers many advantages. A monitoring method was developed using near-infrared (NIR) measurements with Teflon tubing as a sample container for the quantification of components in the indium-tin-oxide (ITO) etching solution composed of hydrochloric acid (HCl), acetic acid (CH3COOH) and water. Measurements were reproducible and it was possible to use the same calibration model for different Teflon tubings. Even though partial least squares (PLS) calibration performance was slightly degraded for Teflon cells when compared to quartz cells of the similar pathlength, the calibration data correlated well with reference data. The robustness of Teflon-based NIR measurement was evaluated by predicting the spectra of 10 independent samples that were collected using five different Teflon tubes. Although, two Teflon tubes were visually less transparent than the other three, there was no significant variation in the standard error of predictions (SEPs) among the five Teflon tubes. Calibration accuracy was successfully maintained and highly repeatable prediction results were achieved. This study verifies that a Teflon-based NIR measurement is reliable for the monitoring of etching solutions and it can be successfully integrated into on-line process monitoring.
Keywords: Near-infrared spectroscopy; Indium-tin-oxide (ITO) etching solution; Teflon
Determination of critical micelle concentrations and aggregation numbers by fluorescence correlation spectroscopy: Aggregation of a lipopolysaccharide by Lanlan Yu; Minyi Tan; Bow Ho; Jeak Ling Ding; Thorsten Wohland (pp. 216-225).
Fluorescence correlation spectroscopy (FCS) is often used to determine the mass or radius of a particle by using the dependence of the diffusion coefficient on the mass and shape. In this article we discuss how the particle size of aggregates can be measured by using the concentration dependence of the amplitude of the autocorrelation function (ACF) instead of the temporal decay. We titrate a solution of aggregates or micelles with a fluorescent label that possesses a high affinity for these structures and measure the changes in the amplitude of the ACF. We develop the theory describing the change of the ACF amplitude with increasing concentrations of labels and use it to fit experimental data. It is shown how this method can determine the aggregation number and critical micelle concentration of a standard detergent nonaethylene glycol monododecyl ether (C12E9) and a lipopolysaccharide (LPS: Escherichia coli 0111:B4).
Keywords: Lipopolysaccharide; Critical micelle concentration; Fluorescence correlation spectroscopy
Determination of critical micelle concentrations and aggregation numbers by fluorescence correlation spectroscopy: Aggregation of a lipopolysaccharide by Lanlan Yu; Minyi Tan; Bow Ho; Jeak Ling Ding; Thorsten Wohland (pp. 216-225).
Fluorescence correlation spectroscopy (FCS) is often used to determine the mass or radius of a particle by using the dependence of the diffusion coefficient on the mass and shape. In this article we discuss how the particle size of aggregates can be measured by using the concentration dependence of the amplitude of the autocorrelation function (ACF) instead of the temporal decay. We titrate a solution of aggregates or micelles with a fluorescent label that possesses a high affinity for these structures and measure the changes in the amplitude of the ACF. We develop the theory describing the change of the ACF amplitude with increasing concentrations of labels and use it to fit experimental data. It is shown how this method can determine the aggregation number and critical micelle concentration of a standard detergent nonaethylene glycol monododecyl ether (C12E9) and a lipopolysaccharide (LPS: Escherichia coli 0111:B4).
Keywords: Lipopolysaccharide; Critical micelle concentration; Fluorescence correlation spectroscopy
Determination of molecular weight profile for a bioactive β-(1→3) polysaccharides ( Curdlan) by T.-W.D. Chan; P.K. Chan; K.Y. Tang (pp. 226-236).
This paper focuses on the development of methodology based on MALDI–TOF mass spectrometry for evaluation of molecular weight profile of the water-insoluble portion of an extracellular polysaccharide, i.e. Curdlan. As previously demonstrated, MALDI analysis of water-insoluble Curdlan fraction gave number-average(M¯n) and weight-average(M¯w) molecular weights of 8000 and 8700Da, respectively [T.W.D. Chan, K.Y. Tang, Rapid Commun. Mass Spectrom. 17 (2003) 887]. To validate the MALDI determined molecular weight information, several additional analytical schemes were used to analysis the water-insoluble Curdlan fraction. In all cases, the water-insoluble Curdlan sample was fractionated by gel permeation chromatography (GPC) using Sephadex G-75 column. TheM¯n of low-mass and narrow distributed polysaccharide fractions were obtained by MALDI–MS. Good linearity was found in the calibration plot constructed from the measuredM¯n-values and the corresponding elution time/volume. The relative quantity of various fractionated samples was then measured using three different approaches. These include (a) direct refractometric analysis; (b) UV–vis absorption analysis of the Aniline Blue stained sample; and (c) GC–MS analysis of the hydrolyzed and TMS-derivatized sample. Using results obtained from theses quantification methods and the correlation function between the GPC retention time andM¯n, the MW and MWD of water-insoluble Curdlan were obtained. Our results demonstrated that the previous use of MALDI methods for measuringM¯n,M¯w and polydispersity (PD) of water-insoluble Curdlan (with and without GPC fractionation) were unreliable. However, by standardizing the narrow distributed polysaccharides using MALDI–MS method, reliable molecular weight information for dispersed polysaccharides could be obtained. TheM¯n,M¯w and PD of the water-insoluble Curdlan were found to be 22,000, 31,500Da and 1.40, respectively.
Keywords: Polysaccharides; MALDI; Mass spectrometry; Molecular weight
Determination of molecular weight profile for a bioactive β-(1→3) polysaccharides ( Curdlan) by T.-W.D. Chan; P.K. Chan; K.Y. Tang (pp. 226-236).
This paper focuses on the development of methodology based on MALDI–TOF mass spectrometry for evaluation of molecular weight profile of the water-insoluble portion of an extracellular polysaccharide, i.e. Curdlan. As previously demonstrated, MALDI analysis of water-insoluble Curdlan fraction gave number-average(M¯n) and weight-average(M¯w) molecular weights of 8000 and 8700Da, respectively [T.W.D. Chan, K.Y. Tang, Rapid Commun. Mass Spectrom. 17 (2003) 887]. To validate the MALDI determined molecular weight information, several additional analytical schemes were used to analysis the water-insoluble Curdlan fraction. In all cases, the water-insoluble Curdlan sample was fractionated by gel permeation chromatography (GPC) using Sephadex G-75 column. TheM¯n of low-mass and narrow distributed polysaccharide fractions were obtained by MALDI–MS. Good linearity was found in the calibration plot constructed from the measuredM¯n-values and the corresponding elution time/volume. The relative quantity of various fractionated samples was then measured using three different approaches. These include (a) direct refractometric analysis; (b) UV–vis absorption analysis of the Aniline Blue stained sample; and (c) GC–MS analysis of the hydrolyzed and TMS-derivatized sample. Using results obtained from theses quantification methods and the correlation function between the GPC retention time andM¯n, the MW and MWD of water-insoluble Curdlan were obtained. Our results demonstrated that the previous use of MALDI methods for measuringM¯n,M¯w and polydispersity (PD) of water-insoluble Curdlan (with and without GPC fractionation) were unreliable. However, by standardizing the narrow distributed polysaccharides using MALDI–MS method, reliable molecular weight information for dispersed polysaccharides could be obtained. TheM¯n,M¯w and PD of the water-insoluble Curdlan were found to be 22,000, 31,500Da and 1.40, respectively.
Keywords: Polysaccharides; MALDI; Mass spectrometry; Molecular weight
Improved analysis of membrane protein by PVDF-aided, matrix-assisted laser desorption/ionization mass spectrometry by Chih-Yang Chang; Hsin-Kai Liao; Chiun-Gung Juo; Shu-Hua Chen; Yu-Ju Chen (pp. 237-246).
Characterization of membrane proteins remains an analytical challenge because of difficulties associated with tedious isolation and purification. This study presents the utility of the polyvinylidene difluoride (PVDF) membrane for direct sub-proteome profiling and membrane protein characterization by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The hydrophobic adsorption of protein, particularly membrane proteins, on the PVDF surface enables efficient on-PVDF washing to remove high concentrations of detergents and salts, such as up to 5% sodium dodecyl sulfate (SDS). The enhanced spectrum quality for MALDI detection is particularly notable for high molecular weight proteins. By using on-PVDF washing prior to MALDI detection, we obtained protein profiles of the detergent-containing and detergent-insoluble membrane fractions from Methylococcus capsulatus (Bath). Similar improvements of signal-to-noise ratios were shown on the MALDI spectra for proteins electroblotted from SDS-polyacrylamide gel electrophoresis (SDS-PAGE) onto the PVDF membrane. We have applied this strategy to obtain intact molecular weights of the particulate methane monooxygenase (pMMO) composed of three intrinsic membrane-bound proteins, PmoA, PmoB, and PmoC. Together with peptide sequencing by tandem mass spectrometry, post-translational modifications including N-terminal acetylation of PmoA and PmoC and alternative C-terminal truncation of PmoB were identified. The above results show that PVDF-aided MALDI-MS can be an effective approach for profiling and characterization of membrane proteins.
Keywords: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry; Membrane protein; Polyvinylidene difluoride
Improved analysis of membrane protein by PVDF-aided, matrix-assisted laser desorption/ionization mass spectrometry by Chih-Yang Chang; Hsin-Kai Liao; Chiun-Gung Juo; Shu-Hua Chen; Yu-Ju Chen (pp. 237-246).
Characterization of membrane proteins remains an analytical challenge because of difficulties associated with tedious isolation and purification. This study presents the utility of the polyvinylidene difluoride (PVDF) membrane for direct sub-proteome profiling and membrane protein characterization by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The hydrophobic adsorption of protein, particularly membrane proteins, on the PVDF surface enables efficient on-PVDF washing to remove high concentrations of detergents and salts, such as up to 5% sodium dodecyl sulfate (SDS). The enhanced spectrum quality for MALDI detection is particularly notable for high molecular weight proteins. By using on-PVDF washing prior to MALDI detection, we obtained protein profiles of the detergent-containing and detergent-insoluble membrane fractions from Methylococcus capsulatus (Bath). Similar improvements of signal-to-noise ratios were shown on the MALDI spectra for proteins electroblotted from SDS-polyacrylamide gel electrophoresis (SDS-PAGE) onto the PVDF membrane. We have applied this strategy to obtain intact molecular weights of the particulate methane monooxygenase (pMMO) composed of three intrinsic membrane-bound proteins, PmoA, PmoB, and PmoC. Together with peptide sequencing by tandem mass spectrometry, post-translational modifications including N-terminal acetylation of PmoA and PmoC and alternative C-terminal truncation of PmoB were identified. The above results show that PVDF-aided MALDI-MS can be an effective approach for profiling and characterization of membrane proteins.
Keywords: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry; Membrane protein; Polyvinylidene difluoride
Simultaneous spectrophotometric determination of iron, nickel and cobalt in micellar media by using direct orthogonal signal correction-partial least squares method by K. Zarei; M. Atabati; Z. Malekshabani (pp. 247-254).
A very simple and selective spectrophotometric method for simultaneous determination of iron(II), nickel(II) and cobalt(II) based on formation of their complexes with 1-(2-pyridylazo)-2-naphtol (PAN) in micellar media is described. Although the complexes of Fe(II), Ni(II) and Co(II) with reagent show a spectral overlap, they have been simultaneously determined by partial least squares (PLS) with and without preprocessing step using direct orthogonal signal correction (DOSC). The linear range was 0.30–4.50μgml−1 for Co(II), 0.20–3.00μgml−1 for Ni(II) and 0.30–5.00μgml−1 for Fe(II). The results obtained by the PLS and DOSC–PLS were statistically compared. Interference effects of common anions and cations were studied and the proposed method was also applied satisfactorily to the determination of Fe(II), Ni(II) and Co(II) in synthetic samples.
Keywords: Direct orthogonal signal correction; PLS; Iron; Nickel; Cobalt; PAN
Simultaneous spectrophotometric determination of iron, nickel and cobalt in micellar media by using direct orthogonal signal correction-partial least squares method by K. Zarei; M. Atabati; Z. Malekshabani (pp. 247-254).
A very simple and selective spectrophotometric method for simultaneous determination of iron(II), nickel(II) and cobalt(II) based on formation of their complexes with 1-(2-pyridylazo)-2-naphtol (PAN) in micellar media is described. Although the complexes of Fe(II), Ni(II) and Co(II) with reagent show a spectral overlap, they have been simultaneously determined by partial least squares (PLS) with and without preprocessing step using direct orthogonal signal correction (DOSC). The linear range was 0.30–4.50μgml−1 for Co(II), 0.20–3.00μgml−1 for Ni(II) and 0.30–5.00μgml−1 for Fe(II). The results obtained by the PLS and DOSC–PLS were statistically compared. Interference effects of common anions and cations were studied and the proposed method was also applied satisfactorily to the determination of Fe(II), Ni(II) and Co(II) in synthetic samples.
Keywords: Direct orthogonal signal correction; PLS; Iron; Nickel; Cobalt; PAN