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Analytica Chimica Acta (v.590, #1)
Sample handling strategies for the determination of persistent trace organic contaminants from biota samples by Natalia Fidalgo-Used; Elisa Blanco-González; Alfredo Sanz-Medel (pp. 1-16).
Even after emergence of most advanced instrumental techniques for the final separation, detection, identification and determination of analytes, sample handling continues to play a basic role in environmental analysis of complex matrices. In fact, sample preparation steps are often the bottleneck for combined time and efficiency in many overall analytical procedures. Thus, it is not surprising that, in the last two decades, a lot of effort has been devoted to the development of faster, safer, and more environment friendly techniques for sample extraction and extract clean up, prior to actual instrumental analysis. This article focuses on the state of the art in sample preparation of environmental solid biological samples dedicated to persistent organic pollutants (POPs) analysis. Extraction techniques such as Soxhlet extraction, sonication-assisted extraction, supercritical fluid extraction (SFE), microwave-assisted extraction (MAE), pressurised liquid extraction (PLE) and matrix solid-phase dispersion (MSPD) are reviewed and their most recent applications to the determination of POPs in biota samples are provided. Additionally, classical as well as promising novel extraction/clean-up techniques such as solid phase microextraction (SPME) are also summarized. Finally, emerging trends in sample preparation able to integrate analytes extraction and their adequate clean-up are presented.
Keywords: Biota samples; Sample preparation; Sample handling; Extract clean-up; Extraction; Persistent organic pollutants
Sample handling strategies for the determination of persistent trace organic contaminants from biota samples by Natalia Fidalgo-Used; Elisa Blanco-González; Alfredo Sanz-Medel (pp. 1-16).
Even after emergence of most advanced instrumental techniques for the final separation, detection, identification and determination of analytes, sample handling continues to play a basic role in environmental analysis of complex matrices. In fact, sample preparation steps are often the bottleneck for combined time and efficiency in many overall analytical procedures. Thus, it is not surprising that, in the last two decades, a lot of effort has been devoted to the development of faster, safer, and more environment friendly techniques for sample extraction and extract clean up, prior to actual instrumental analysis. This article focuses on the state of the art in sample preparation of environmental solid biological samples dedicated to persistent organic pollutants (POPs) analysis. Extraction techniques such as Soxhlet extraction, sonication-assisted extraction, supercritical fluid extraction (SFE), microwave-assisted extraction (MAE), pressurised liquid extraction (PLE) and matrix solid-phase dispersion (MSPD) are reviewed and their most recent applications to the determination of POPs in biota samples are provided. Additionally, classical as well as promising novel extraction/clean-up techniques such as solid phase microextraction (SPME) are also summarized. Finally, emerging trends in sample preparation able to integrate analytes extraction and their adequate clean-up are presented.
Keywords: Biota samples; Sample preparation; Sample handling; Extract clean-up; Extraction; Persistent organic pollutants
Optimisation of a matrix solid-phase dispersion method for the determination of organophosphate compounds in dust samples by M. García; I. Rodríguez; R. Cela (pp. 17-25).
A fast and inexpensive sample preparation procedure based on the matrix solid-phase dispersion (MSPD) technique is proposed for the isolation of several organophosphate esters (mainly employed as flame retardants and plasticizers) from indoor dust samples. Extraction and clean-up were carried out in a single step and target compounds were determined by gas chromatography (GC) with nitrogen–phosphorus detection (NPD). The main parameters affecting extraction yield and selectivity, such as type and amount of dispersant material, clean-up co-sorbent and extraction solvent, were evaluated and optimised. Under final conditions, 0.5g of dust were dispersed with equal amounts of anhydrous sodium sulphate and Florisil, and loaded on the top of a polypropylene cartridge containing 0.5g of alumina. The dispersed sample was washed with 2mL of n-hexane to remove the least polar interferences and analytes were eluted with 3mL of acetone. Recoveries of the proposed method for spiked samples ranged from 80 to 116%, and the day-to-day variability remained between 5 and 10%. Data on levels of organophosphate species in dust from private houses and vehicle cabins are provided. In both cases, the lowest concentrations corresponded to the short chain, non-chlorinated, alkyl organophosphates, whereas mean values above 1μgg−1 were measured for the rest of analytes.
Keywords: Organophosphate compounds; Dust; Matrix solid-phase dispersion; Gas chromatography
Optimisation of a matrix solid-phase dispersion method for the determination of organophosphate compounds in dust samples by M. García; I. Rodríguez; R. Cela (pp. 17-25).
A fast and inexpensive sample preparation procedure based on the matrix solid-phase dispersion (MSPD) technique is proposed for the isolation of several organophosphate esters (mainly employed as flame retardants and plasticizers) from indoor dust samples. Extraction and clean-up were carried out in a single step and target compounds were determined by gas chromatography (GC) with nitrogen–phosphorus detection (NPD). The main parameters affecting extraction yield and selectivity, such as type and amount of dispersant material, clean-up co-sorbent and extraction solvent, were evaluated and optimised. Under final conditions, 0.5g of dust were dispersed with equal amounts of anhydrous sodium sulphate and Florisil, and loaded on the top of a polypropylene cartridge containing 0.5g of alumina. The dispersed sample was washed with 2mL of n-hexane to remove the least polar interferences and analytes were eluted with 3mL of acetone. Recoveries of the proposed method for spiked samples ranged from 80 to 116%, and the day-to-day variability remained between 5 and 10%. Data on levels of organophosphate species in dust from private houses and vehicle cabins are provided. In both cases, the lowest concentrations corresponded to the short chain, non-chlorinated, alkyl organophosphates, whereas mean values above 1μgg−1 were measured for the rest of analytes.
Keywords: Organophosphate compounds; Dust; Matrix solid-phase dispersion; Gas chromatography
pH-resistant titania hybrid organic–inorganic sol–gel coating for solid-phase microextraction of polar compounds by Xiujuan Li; Jie Gao; Zhaorui Zeng (pp. 26-33).
A novel titania-hydroxy-terminated silicone oil (titania-OH-TSO) sol–gel coating was developed for solid-phase microextraction of polar compounds. In general, titania-based sol–gel reaction is very fast and need to be decelerated by the use of suitable chelating agents. But in the present work, a judiciously designed sol solution ingredients was used to create the titania-OH-TSO coating without the addition of any chelating agent, which simplified the sol–gel procedure. Thanks to the variety of titania's adsorption sites and their acid–base characteristics, aromatic amines, phenols and polycyclic aromatic hydrocarbons were efficiently extracted and preconcentrated from aqueous samples followed by thermal desorption and GC analysis. The newly developed sol–gel hybrid titania coating demonstrated excellent pH stability, and retained its extraction characteristics intact even after continuous rinsing with a 3M HCl or NaOH solution for 12h. Furthermore, it could withstand temperatures as high as 320°C. Practical application was demonstrated through the analysis of six aromatic amines in dye process wastewater. A linearity of four orders of magnitude was obtained with correlation coefficient better than 0.9982. The detection limits ranged from 0.22 to 0.84μgL−1 and the repeatability of the measurements was <7.0%. The recoveries of these compounds studied in the wastewater were in the ranges 83.6–101.4%, indicating the method accuracy.
Keywords: Solid-phase microextraction; Sol–gel; Titania; Aromatic amines; Phenols; Polycyclic aromatic hydrocarbons; Dye process wastewater
pH-resistant titania hybrid organic–inorganic sol–gel coating for solid-phase microextraction of polar compounds by Xiujuan Li; Jie Gao; Zhaorui Zeng (pp. 26-33).
A novel titania-hydroxy-terminated silicone oil (titania-OH-TSO) sol–gel coating was developed for solid-phase microextraction of polar compounds. In general, titania-based sol–gel reaction is very fast and need to be decelerated by the use of suitable chelating agents. But in the present work, a judiciously designed sol solution ingredients was used to create the titania-OH-TSO coating without the addition of any chelating agent, which simplified the sol–gel procedure. Thanks to the variety of titania's adsorption sites and their acid–base characteristics, aromatic amines, phenols and polycyclic aromatic hydrocarbons were efficiently extracted and preconcentrated from aqueous samples followed by thermal desorption and GC analysis. The newly developed sol–gel hybrid titania coating demonstrated excellent pH stability, and retained its extraction characteristics intact even after continuous rinsing with a 3M HCl or NaOH solution for 12h. Furthermore, it could withstand temperatures as high as 320°C. Practical application was demonstrated through the analysis of six aromatic amines in dye process wastewater. A linearity of four orders of magnitude was obtained with correlation coefficient better than 0.9982. The detection limits ranged from 0.22 to 0.84μgL−1 and the repeatability of the measurements was <7.0%. The recoveries of these compounds studied in the wastewater were in the ranges 83.6–101.4%, indicating the method accuracy.
Keywords: Solid-phase microextraction; Sol–gel; Titania; Aromatic amines; Phenols; Polycyclic aromatic hydrocarbons; Dye process wastewater
Determination of triazine herbicides in sheep liver by microwave-assisted extraction and high performance liquid chromatography by Jianhua Cheng; Miao Liu; Xinyou Zhang; Lan Ding; Yong Yu; Xiupin Wang; Haiyan Jin; Hanqi Zhang (pp. 34-39).
A multi-residue method developed for the analysis of triazine herbicides, simazine, atrazine, propazine and prometryne, in sheep liver is presented. The method is based on microwave-assisted extraction (MAE) of sheep liver using methanol as extractant and analysis of extracts by high performance liquid chromatography (HPLC) and ultraviolet detection. MAE operational parameters, the solvent type and volume, extraction temperature and time, were optimized in detail with respect to extraction efficiency of the target compounds from sheep liver. The recoveries of the method at two different spiked levels were assessed by analyzing spiked liver samples and were found to be in the range from 90 to 102% with good precision (<11%).
Keywords: Microwave-assisted extraction; Triazine; Simazine; Atrazine; Propazine; Prometryne; High performance liquid chromatography; Sheep liver
Determination of triazine herbicides in sheep liver by microwave-assisted extraction and high performance liquid chromatography by Jianhua Cheng; Miao Liu; Xinyou Zhang; Lan Ding; Yong Yu; Xiupin Wang; Haiyan Jin; Hanqi Zhang (pp. 34-39).
A multi-residue method developed for the analysis of triazine herbicides, simazine, atrazine, propazine and prometryne, in sheep liver is presented. The method is based on microwave-assisted extraction (MAE) of sheep liver using methanol as extractant and analysis of extracts by high performance liquid chromatography (HPLC) and ultraviolet detection. MAE operational parameters, the solvent type and volume, extraction temperature and time, were optimized in detail with respect to extraction efficiency of the target compounds from sheep liver. The recoveries of the method at two different spiked levels were assessed by analyzing spiked liver samples and were found to be in the range from 90 to 102% with good precision (<11%).
Keywords: Microwave-assisted extraction; Triazine; Simazine; Atrazine; Propazine; Prometryne; High performance liquid chromatography; Sheep liver
Determination of molybdenum in environmental samples by Krystyna Pyrzynska (pp. 40-48).
Determination of molybdenum in different kinds of environmental samples is often a challenging task for analysts. Its concentration is usually very low and the sample matrix may cause serious interferences during measurement. Therefore, preconcentration and separation methods should be used to solve these problems and render more sensitive, accurate and interference-free determination. Recent developments in sample treatment, such as solid phase and liquid–liquid extraction as well as coprecipitation are presented, including flow-based methodology. In addition, important extension and improvements in analytical methods for determinations of molybdenum are updated. Some examples of speciation analysis are also presented.
Keywords: Molybdenum determination; Preconcentration; Separation methods; Environmental analysis
Determination of molybdenum in environmental samples by Krystyna Pyrzynska (pp. 40-48).
Determination of molybdenum in different kinds of environmental samples is often a challenging task for analysts. Its concentration is usually very low and the sample matrix may cause serious interferences during measurement. Therefore, preconcentration and separation methods should be used to solve these problems and render more sensitive, accurate and interference-free determination. Recent developments in sample treatment, such as solid phase and liquid–liquid extraction as well as coprecipitation are presented, including flow-based methodology. In addition, important extension and improvements in analytical methods for determinations of molybdenum are updated. Some examples of speciation analysis are also presented.
Keywords: Molybdenum determination; Preconcentration; Separation methods; Environmental analysis
Improved quality control in gas chromatography interfaced to stable isotope ratio mass spectrometry by application of derivative chromatography by Walter Vetter; Simon Gaul; Joachim Melcher (pp. 49-54).
Compound-specific isotope analysis using gas chromatography interfaced to isotope ratio mass spectrometry (GC-IRMS) is a versatile technique for applications ranging from source appointment and the elucidation of biochemical pathways. When δ13C values are going to be determined, the sample is combusted to CO2 and the resulting gas is analyzed relative to a standard with known stable carbon isotope ratio. With the combustion step any information on the identity of a peak is lost. Co-eluting compounds can no more be identified which can lead to significant alterations of the δ13C value of the analyte. For improvement of the QA/QC protocols in GC-IRMS, we used first, second, and third order derivative chromatography. The suitability of the technique was studied using mixtures of 2,3,3′,4,4′,5,5′-heptachloro-1′-methyl-1,2′-bipyrrole (Q1) and 2,2′,4,5,5′-pentachlorobiphenyl (PCB 101). By application of different GC oven programs four scenarios ranging from baseline separation to full co-elution were obtained. Derivative chromatography enabled identification of the interference of Q1 with PCB 101 even when both peaks fully co-eluted. Although the δ13C values could not be determined from interfered scenarios, the use of derivative spectroscopy will help to prevent acceptance of incorrect data due to co-elutions. Derivative chromatography was finally used to study the peak purity of 2,2′,3,4,4′-pentabromodiphenyl ether (BDE 85) in technical pentabromo diphenyl ether (DE-71). Already the first order derivative demonstrated that this key-BDE congener was interfered by a compound identified as 2,2′,4,4′,6,6′-hexabromodiphenyl ether (BDE 155).
Keywords: Stable carbon isotope analysis; Compound-specific isotope analysis; Gas chromatography interfaced to isotope ratio mass spectrometry; Persistent organic pollutants; Peak overlap; Derivative chromatography
Improved quality control in gas chromatography interfaced to stable isotope ratio mass spectrometry by application of derivative chromatography by Walter Vetter; Simon Gaul; Joachim Melcher (pp. 49-54).
Compound-specific isotope analysis using gas chromatography interfaced to isotope ratio mass spectrometry (GC-IRMS) is a versatile technique for applications ranging from source appointment and the elucidation of biochemical pathways. When δ13C values are going to be determined, the sample is combusted to CO2 and the resulting gas is analyzed relative to a standard with known stable carbon isotope ratio. With the combustion step any information on the identity of a peak is lost. Co-eluting compounds can no more be identified which can lead to significant alterations of the δ13C value of the analyte. For improvement of the QA/QC protocols in GC-IRMS, we used first, second, and third order derivative chromatography. The suitability of the technique was studied using mixtures of 2,3,3′,4,4′,5,5′-heptachloro-1′-methyl-1,2′-bipyrrole (Q1) and 2,2′,4,5,5′-pentachlorobiphenyl (PCB 101). By application of different GC oven programs four scenarios ranging from baseline separation to full co-elution were obtained. Derivative chromatography enabled identification of the interference of Q1 with PCB 101 even when both peaks fully co-eluted. Although the δ13C values could not be determined from interfered scenarios, the use of derivative spectroscopy will help to prevent acceptance of incorrect data due to co-elutions. Derivative chromatography was finally used to study the peak purity of 2,2′,3,4,4′-pentabromodiphenyl ether (BDE 85) in technical pentabromo diphenyl ether (DE-71). Already the first order derivative demonstrated that this key-BDE congener was interfered by a compound identified as 2,2′,4,4′,6,6′-hexabromodiphenyl ether (BDE 155).
Keywords: Stable carbon isotope analysis; Compound-specific isotope analysis; Gas chromatography interfaced to isotope ratio mass spectrometry; Persistent organic pollutants; Peak overlap; Derivative chromatography
Evaluation of strontium isotope abundance ratios in combination with multi-elemental analysis as a possible tool to study the geographical origin of ciders by Silvia García-Ruiz; Mariella Moldovan; Giuseppino Fortunato; Samuel Wunderli; J. Ignacio García Alonso (pp. 55-66).
In order to evaluate alternative analytical methodologies to study the geographical origin of ciders, both multi-elemental analysis and Sr isotope abundance ratios in combination with multivariate statistical analysis were estimated in 67 samples from England, Switzerland, France and two Spanish regions (Asturias and the Basque Country). A methodology for the precise and accurate determination of the87Sr/86Sr isotope abundance ratio in ciders by multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) was developed. Major elements (Na, K, Ca and Mg) were measured by ICP-AES and minor and trace elements (Li, Be, B, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Y, Mo, Cd, Sn, Sb, Cs, Ba, La, Ce, W, Tl, Pb, Bi, Th and U) were measured by ICP-MS using a collision cell instrument operated in multitune mode. An analysis of variance (ANOVA test) indicated that group means for B, Cr, Fe, Ni, Cu, Se, Cd, Cs, Ce, W, Pb, Bi and U did not show any significant differences at the 95% confidence level, so these elements were rejected for further statistical analysis. Another group of elements (Li, Be, Sc, Co, Ga, Y, Sn, Sb, La, Tl, Th) was removed from the data set because concentrations were close to the limits of detection for many samples. Therefore, the remaining elements (Na, Mg, Al, K, Ca, Ti, V, Mn, Zn, As, Rb, Sr, Mo, Ba) together with87Sr/86Sr isotope abundance ratio were considered for principal component analysis (PCA) and linear discriminant analysis (LDA). Finally, LDA was able to classify correctly 100% of cider samples coming from different Spanish regions, France, England and Switzerland when considering Na, Mg, Al, K, Ca, Ti, V, Mn, Zn, As, Rb, Sr, Mo, Ba and87Sr/86Sr isotope abundance ratio as original variables.
Keywords: Food authentication; Beverages; Ciders; Strontium isotope abundance ratios; Multicollector; Inductively coupled plasma mass spectrometry; Multi-elemental analysis; Inductively coupled plasma atomic emission spectrometry
Evaluation of strontium isotope abundance ratios in combination with multi-elemental analysis as a possible tool to study the geographical origin of ciders by Silvia García-Ruiz; Mariella Moldovan; Giuseppino Fortunato; Samuel Wunderli; J. Ignacio García Alonso (pp. 55-66).
In order to evaluate alternative analytical methodologies to study the geographical origin of ciders, both multi-elemental analysis and Sr isotope abundance ratios in combination with multivariate statistical analysis were estimated in 67 samples from England, Switzerland, France and two Spanish regions (Asturias and the Basque Country). A methodology for the precise and accurate determination of the87Sr/86Sr isotope abundance ratio in ciders by multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) was developed. Major elements (Na, K, Ca and Mg) were measured by ICP-AES and minor and trace elements (Li, Be, B, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Y, Mo, Cd, Sn, Sb, Cs, Ba, La, Ce, W, Tl, Pb, Bi, Th and U) were measured by ICP-MS using a collision cell instrument operated in multitune mode. An analysis of variance (ANOVA test) indicated that group means for B, Cr, Fe, Ni, Cu, Se, Cd, Cs, Ce, W, Pb, Bi and U did not show any significant differences at the 95% confidence level, so these elements were rejected for further statistical analysis. Another group of elements (Li, Be, Sc, Co, Ga, Y, Sn, Sb, La, Tl, Th) was removed from the data set because concentrations were close to the limits of detection for many samples. Therefore, the remaining elements (Na, Mg, Al, K, Ca, Ti, V, Mn, Zn, As, Rb, Sr, Mo, Ba) together with87Sr/86Sr isotope abundance ratio were considered for principal component analysis (PCA) and linear discriminant analysis (LDA). Finally, LDA was able to classify correctly 100% of cider samples coming from different Spanish regions, France, England and Switzerland when considering Na, Mg, Al, K, Ca, Ti, V, Mn, Zn, As, Rb, Sr, Mo, Ba and87Sr/86Sr isotope abundance ratio as original variables.
Keywords: Food authentication; Beverages; Ciders; Strontium isotope abundance ratios; Multicollector; Inductively coupled plasma mass spectrometry; Multi-elemental analysis; Inductively coupled plasma atomic emission spectrometry
Combinatorial electrochemistry using metal nanoparticles: From proof-of-concept to practical realisation for bromide detection by Biljana Šljukić; Ronan Baron; Chris Salter; Alison Crossley; Richard G. Compton (pp. 67-73).
Principles and practical application of combinatorial electrochemistry in search for new electroactive materials in electroanalysis have been explored. Nanoparticles of three different metals: silver, gold and palladium have been independently synthesized on the glassy carbon spherical powder surface by electroless deposition process and characterized using both spectroscopic and electrochemical techniques. These three materials were then combined together onto basal plane pyrolytic graphite electrode surface and the application of the combinatorial approach to find the electrode material for bromide detection as model target analyte was demonstrated. The component electroactive for bromide detection was next identified and it was found that silver nanoparticles were the active ones. A composite electrode based on silver nanoparticle modified glassy carbon powder and epoxy resin was then fabricated and it was found to allow accurate determination of bromide. The electroactivity for the bromide determination of the composite electrode was compared with that of a bulk silver electrode and it was shown that the composite electrode is very efficient with a comparable electroactivity with only a portion of precious metals being used for its construction.
Keywords: Combinatorial electrochemistry; Metal nanoparticle; Electroless deposition; Composite electrode; Bromide
Combinatorial electrochemistry using metal nanoparticles: From proof-of-concept to practical realisation for bromide detection by Biljana Šljukić; Ronan Baron; Chris Salter; Alison Crossley; Richard G. Compton (pp. 67-73).
Principles and practical application of combinatorial electrochemistry in search for new electroactive materials in electroanalysis have been explored. Nanoparticles of three different metals: silver, gold and palladium have been independently synthesized on the glassy carbon spherical powder surface by electroless deposition process and characterized using both spectroscopic and electrochemical techniques. These three materials were then combined together onto basal plane pyrolytic graphite electrode surface and the application of the combinatorial approach to find the electrode material for bromide detection as model target analyte was demonstrated. The component electroactive for bromide detection was next identified and it was found that silver nanoparticles were the active ones. A composite electrode based on silver nanoparticle modified glassy carbon powder and epoxy resin was then fabricated and it was found to allow accurate determination of bromide. The electroactivity for the bromide determination of the composite electrode was compared with that of a bulk silver electrode and it was shown that the composite electrode is very efficient with a comparable electroactivity with only a portion of precious metals being used for its construction.
Keywords: Combinatorial electrochemistry; Metal nanoparticle; Electroless deposition; Composite electrode; Bromide
Development of fast Fourier transform continuous cyclic voltammetry at Au microelectrode in flowing solutions as a novel method for sub-nanomolar monitoring of lidocaine in injection and biological fluids by P. Norouzi; M.R. Ganjali; P. Daneshgar; R. Dinarvand; A.A. Moosavi-Movahedi; A.A. Saboury (pp. 74-80).
In this work a novel method for the fast monitoring of lidocaine in flow-injection systems has been developed. The fast Fourier transform continuous cyclic voltammetry (FFTCV) at gold microelectrode in flowing solution system was used for determination of lidocaine in its pharmaceutical formulation. The presented technique was very simple, precise, accurate, time saving and economical, compared with all of the previously reported methods. The recommended technique demonstrated some advantages over other reported methods. Firstly, there was no need for the oxygen removal from the test solution. Secondly, a picomolar detection limit was achieved, and additionally, the method was fast enough for the determination of any such compound, in a wide variety of chromatographic methods. The method was linear across the concentration range of 240–1.1×105pgmL−1 ( r=0.996) with a limit of detection and quantitation 117.3 and 240pgmL−1, respectively. As a conclusion this system offers the requisite accuracy, sensitivity, precision and selectivity to assay lidocaine in injections.
Keywords: Lidocaine; Fourier transform; Flow injection; Ultramicroelectrode
Development of fast Fourier transform continuous cyclic voltammetry at Au microelectrode in flowing solutions as a novel method for sub-nanomolar monitoring of lidocaine in injection and biological fluids by P. Norouzi; M.R. Ganjali; P. Daneshgar; R. Dinarvand; A.A. Moosavi-Movahedi; A.A. Saboury (pp. 74-80).
In this work a novel method for the fast monitoring of lidocaine in flow-injection systems has been developed. The fast Fourier transform continuous cyclic voltammetry (FFTCV) at gold microelectrode in flowing solution system was used for determination of lidocaine in its pharmaceutical formulation. The presented technique was very simple, precise, accurate, time saving and economical, compared with all of the previously reported methods. The recommended technique demonstrated some advantages over other reported methods. Firstly, there was no need for the oxygen removal from the test solution. Secondly, a picomolar detection limit was achieved, and additionally, the method was fast enough for the determination of any such compound, in a wide variety of chromatographic methods. The method was linear across the concentration range of 240–1.1×105pgmL−1 ( r=0.996) with a limit of detection and quantitation 117.3 and 240pgmL−1, respectively. As a conclusion this system offers the requisite accuracy, sensitivity, precision and selectivity to assay lidocaine in injections.
Keywords: Lidocaine; Fourier transform; Flow injection; Ultramicroelectrode
Neutral carriers based polymeric membrane electrodes for selective determination of mercury (II) by V.K. Gupta; A.K. Singh; M. Al Khayat; Barkha Gupta (pp. 81-90).
The potentiometric response characteristics of mercury ion-selective membrane electrodes based on 2-amino-6-purinethiol (I1) and 5-amino-1, 3, 4-thiadiazole-2-thiol (I2) were described. Ion selectivities were tested for various plasticizers, which were used as solvent mediators to incorporate the ionophores into the membrane. Effects of experimental parameters such as membrane composition, nature and amount of plasticizers and additives, pH and concentration of internal solution on the potential response of Hg2+ electrodes were investigated. The best performance was obtained with the electrode having a membrane composition (w/w) of (I1) (3.17%): PVC (31.7%): DOP (dioctylpthalate) (63.4%): NaTPB (sodium tetraphenylborate) (1.58%). The proposed electrode reveals a Nernstian response over Hg2+ ion in the concentration range of 7.0×10−8–1.0×10−1M with limit of detection 4.4×10−8M. The electrode shows good discrimination toward Hg2+ ion with respect to most common cations. It shows a short response time (10s) for whole concentration range and can be used for 2 months without any considerable divergence in potentials. For evaluation of the analytical applicability, the electrode was used in the determination of Hg2+ ion in different environmental and biological samples. The practical utility of the membrane electrode has also been observed in the presence of surfactants.
Keywords: Neutral ionophore; Poly (vinylchloride) membranes; Mercury; Ion-selective electrodes
Neutral carriers based polymeric membrane electrodes for selective determination of mercury (II) by V.K. Gupta; A.K. Singh; M. Al Khayat; Barkha Gupta (pp. 81-90).
The potentiometric response characteristics of mercury ion-selective membrane electrodes based on 2-amino-6-purinethiol (I1) and 5-amino-1, 3, 4-thiadiazole-2-thiol (I2) were described. Ion selectivities were tested for various plasticizers, which were used as solvent mediators to incorporate the ionophores into the membrane. Effects of experimental parameters such as membrane composition, nature and amount of plasticizers and additives, pH and concentration of internal solution on the potential response of Hg2+ electrodes were investigated. The best performance was obtained with the electrode having a membrane composition (w/w) of (I1) (3.17%): PVC (31.7%): DOP (dioctylpthalate) (63.4%): NaTPB (sodium tetraphenylborate) (1.58%). The proposed electrode reveals a Nernstian response over Hg2+ ion in the concentration range of 7.0×10−8–1.0×10−1M with limit of detection 4.4×10−8M. The electrode shows good discrimination toward Hg2+ ion with respect to most common cations. It shows a short response time (10s) for whole concentration range and can be used for 2 months without any considerable divergence in potentials. For evaluation of the analytical applicability, the electrode was used in the determination of Hg2+ ion in different environmental and biological samples. The practical utility of the membrane electrode has also been observed in the presence of surfactants.
Keywords: Neutral ionophore; Poly (vinylchloride) membranes; Mercury; Ion-selective electrodes
Quartz crystal microbalance biosensor for recombinant human interferon-β detection based on antisense peptide approach by Jia Luo; Qundan Zhang; Yanyan Huang; Guoquan Liu; Rui Zhao (pp. 91-97).
Quartz crystal microbalance (QCM) biosensors for recombinant human interferon-β (rhIFN-β) were constructed by utilizing antisense peptides adhering to the QCM gold surfaces. Two antisense peptides, both corresponding to the N-terminal fragment 1–14 of rhIFN-β, were used in this study. Antisense peptide AS-1 was the original antisense peptide and AS-2 was the modified antisense peptide based on the antisense peptide degeneracy. Both antisense peptides were immobilized on the gold electrodes of piezoelectric crystals, respectively, via a self-assembling monolayer of 1,2-ethanedithiol. The binding affinity between rhIFN-β and each immobilized antisense peptide in solution was evaluated using a quartz crystal microbalance-flow injection analysis (QCM-FIA) system. The dissociation constant of rhIFN-β on the antisense peptide AS-1 and AS-2 biosensor was (1.89±0.101)×10−4 and (1.22±0.0479)×10−5molL−1, respectively. The results suggested that AS-2 had a higher binding affinity to rhIFN-β than AS-1. The detection for rhIFN-β using each biosensor was precise and reproducible. The linear response ranges of rhIFN-β binding to both biosensors were same with a concentration range of 0.12–0.96mgmL−1. The results demonstrated the successful construction of highly selective QCM biosensors using antisense peptide approach, and also confirmed the feasibility of increasing antisense peptide binding affinity by appropriate sequence modification.
Keywords: Quartz crystal microbalance biosensor; Antisense peptide; Recombinant human interferon-β; Flow injection analysis
Quartz crystal microbalance biosensor for recombinant human interferon-β detection based on antisense peptide approach by Jia Luo; Qundan Zhang; Yanyan Huang; Guoquan Liu; Rui Zhao (pp. 91-97).
Quartz crystal microbalance (QCM) biosensors for recombinant human interferon-β (rhIFN-β) were constructed by utilizing antisense peptides adhering to the QCM gold surfaces. Two antisense peptides, both corresponding to the N-terminal fragment 1–14 of rhIFN-β, were used in this study. Antisense peptide AS-1 was the original antisense peptide and AS-2 was the modified antisense peptide based on the antisense peptide degeneracy. Both antisense peptides were immobilized on the gold electrodes of piezoelectric crystals, respectively, via a self-assembling monolayer of 1,2-ethanedithiol. The binding affinity between rhIFN-β and each immobilized antisense peptide in solution was evaluated using a quartz crystal microbalance-flow injection analysis (QCM-FIA) system. The dissociation constant of rhIFN-β on the antisense peptide AS-1 and AS-2 biosensor was (1.89±0.101)×10−4 and (1.22±0.0479)×10−5molL−1, respectively. The results suggested that AS-2 had a higher binding affinity to rhIFN-β than AS-1. The detection for rhIFN-β using each biosensor was precise and reproducible. The linear response ranges of rhIFN-β binding to both biosensors were same with a concentration range of 0.12–0.96mgmL−1. The results demonstrated the successful construction of highly selective QCM biosensors using antisense peptide approach, and also confirmed the feasibility of increasing antisense peptide binding affinity by appropriate sequence modification.
Keywords: Quartz crystal microbalance biosensor; Antisense peptide; Recombinant human interferon-β; Flow injection analysis
A cam-based laser-induced fluorescence scanner for capillary array electrophoresis by Joann J. Lu; Qiaosheng Pu; Shili Wang; Shaorong Liu (pp. 98-103).
Capillary array electrophoresis (CAE) is an important high throughput analytical technique. Laser-induced fluorescence (LIF) has been the dominant detection method for CAE owing to its low limit of detection (LOD) and wide linear dynamic range (LDR). Linear LIF scanners were first used in CAE because linear motions of an objective match well with a common planar array of capillaries. A problem with linear scanners is that the motor is required accelerating/decelerating so that all capillaries can be properly scanned, which makes motion control complicated and reduces the duty cycle. Rotary scanners were developed to overcome this problem. While rotary scanners have been successfully applied in CAE, the capillaries have to be arranged in a circular format, which can be inconvenient in some cases. In this report, we describe a cam-based LIF scanner as an alternative technique for CAE detection. In this system, a rotary motor is mechanically linked with a capillary holder via a cam. During operation, the motor carries the cam in a rotary motion that drives an array of capillaries on the holder to move back and forth across the objective for fluorescence detection. Using this design, the capillaries can be parallel-arranged in a plane while the motor acceleration/deceleration is avoided. To demonstrate the feasibility of this approach, we constructed a prototype instrument with a constant-velocity scanning distance of ∼10mm, a scanning frequency of 3Hz and a duty cycle of ∼70%. The scanner exhibited a LOD of 69pM of fluorescein and a LDR of 3.5 orders of magnitude. Multiplexed capillary SDS-PAGE was performed on this scanner for protein separations.
Keywords: Capillary array electrophoresis; Laser-induced fluorescence scanner; Protein separation
A cam-based laser-induced fluorescence scanner for capillary array electrophoresis by Joann J. Lu; Qiaosheng Pu; Shili Wang; Shaorong Liu (pp. 98-103).
Capillary array electrophoresis (CAE) is an important high throughput analytical technique. Laser-induced fluorescence (LIF) has been the dominant detection method for CAE owing to its low limit of detection (LOD) and wide linear dynamic range (LDR). Linear LIF scanners were first used in CAE because linear motions of an objective match well with a common planar array of capillaries. A problem with linear scanners is that the motor is required accelerating/decelerating so that all capillaries can be properly scanned, which makes motion control complicated and reduces the duty cycle. Rotary scanners were developed to overcome this problem. While rotary scanners have been successfully applied in CAE, the capillaries have to be arranged in a circular format, which can be inconvenient in some cases. In this report, we describe a cam-based LIF scanner as an alternative technique for CAE detection. In this system, a rotary motor is mechanically linked with a capillary holder via a cam. During operation, the motor carries the cam in a rotary motion that drives an array of capillaries on the holder to move back and forth across the objective for fluorescence detection. Using this design, the capillaries can be parallel-arranged in a plane while the motor acceleration/deceleration is avoided. To demonstrate the feasibility of this approach, we constructed a prototype instrument with a constant-velocity scanning distance of ∼10mm, a scanning frequency of 3Hz and a duty cycle of ∼70%. The scanner exhibited a LOD of 69pM of fluorescein and a LDR of 3.5 orders of magnitude. Multiplexed capillary SDS-PAGE was performed on this scanner for protein separations.
Keywords: Capillary array electrophoresis; Laser-induced fluorescence scanner; Protein separation
Quantification of protein based on single-molecule counting by total internal reflection fluorescence microscopy with adsorption equilibrium by Lei Wang; Guang Xu; Zhikun Shi; Wei Jiang; Wenrui Jin (pp. 104-109).
We developed a sensitive single-molecule imaging method for quantification of protein by total internal reflection fluorescence microscopy with adsorption equilibrium. In this method, the adsorption equilibrium of protein was achieved between solution and glass substrate. Then, fluorescence images of protein molecules in a evanescent wave field were taken by a highly sensitive electron multiplying charge coupled device. Finally, the number of fluorescent spots corresponding to the protein molecules in the images was counted. Alexa Fluor 488-labeled goat anti-rat IgG(H+L) was chosen as the model protein. The spot number showed an excellent linear relationship with protein concentration. The concentration linear range was 5.4×10−11 to 8.1×10−10molL−1.
Keywords: Total internal reflection fluorescence microscopy; Single-molecule detection; Protein
Quantification of protein based on single-molecule counting by total internal reflection fluorescence microscopy with adsorption equilibrium by Lei Wang; Guang Xu; Zhikun Shi; Wei Jiang; Wenrui Jin (pp. 104-109).
We developed a sensitive single-molecule imaging method for quantification of protein by total internal reflection fluorescence microscopy with adsorption equilibrium. In this method, the adsorption equilibrium of protein was achieved between solution and glass substrate. Then, fluorescence images of protein molecules in a evanescent wave field were taken by a highly sensitive electron multiplying charge coupled device. Finally, the number of fluorescent spots corresponding to the protein molecules in the images was counted. Alexa Fluor 488-labeled goat anti-rat IgG(H+L) was chosen as the model protein. The spot number showed an excellent linear relationship with protein concentration. The concentration linear range was 5.4×10−11 to 8.1×10−10molL−1.
Keywords: Total internal reflection fluorescence microscopy; Single-molecule detection; Protein
Multiplexing fibre optic near infrared (NIR) spectroscopy as an emerging technology to monitor industrial bioprocesses by Payal Roychoudhury; Ronan O’Kennedy; Brian McNeil; Linda M. Harvey (pp. 110-117).
The application of near infrared spectroscopy in bioprocessing has been limited by its dependence on calibrations derived from single bioreactor at a given time. Here, we propose a multiplexed calibration technique which allows calibrations to be built from multiple bioreactors run in parallel. This gives the flexibility to monitor multiple vessels and facilitates calibration model transfer between bioreactors. Models have been developed for the two key analytes: glucose and lactate using Chinese hamster ovary (CHO) cell lines and using analyte specific information obtained from the feasibility studies. We observe slight model degradation for the multiplexed models in comparison to the conventional (single probe) models, decrease in r2 values from 89.4% to 88% for glucose whereas for lactate from 92% to 91.8% and a simultaneous increase in the number of factors as the model incorporates the inter-probe variability, nevertheless the models were fit for purpose. The results of this particular application of implementing multiplexed-NIRS to monitor multiple bioreactor vessels are very encouraging, as successful models have been built on-line and validated externally, which proffers the prospect of reducing timelines in monitoring the vessels considerably, and in turn, providing improved control.
Keywords: Near infrared spectroscopy; Multiplexed calibration; Chinese hamster ovary; On-line
Multiplexing fibre optic near infrared (NIR) spectroscopy as an emerging technology to monitor industrial bioprocesses by Payal Roychoudhury; Ronan O’Kennedy; Brian McNeil; Linda M. Harvey (pp. 110-117).
The application of near infrared spectroscopy in bioprocessing has been limited by its dependence on calibrations derived from single bioreactor at a given time. Here, we propose a multiplexed calibration technique which allows calibrations to be built from multiple bioreactors run in parallel. This gives the flexibility to monitor multiple vessels and facilitates calibration model transfer between bioreactors. Models have been developed for the two key analytes: glucose and lactate using Chinese hamster ovary (CHO) cell lines and using analyte specific information obtained from the feasibility studies. We observe slight model degradation for the multiplexed models in comparison to the conventional (single probe) models, decrease in r2 values from 89.4% to 88% for glucose whereas for lactate from 92% to 91.8% and a simultaneous increase in the number of factors as the model incorporates the inter-probe variability, nevertheless the models were fit for purpose. The results of this particular application of implementing multiplexed-NIRS to monitor multiple bioreactor vessels are very encouraging, as successful models have been built on-line and validated externally, which proffers the prospect of reducing timelines in monitoring the vessels considerably, and in turn, providing improved control.
Keywords: Near infrared spectroscopy; Multiplexed calibration; Chinese hamster ovary; On-line
Simultaneous non-instrumental detection of aflatoxin B1 and ochratoxin A using a clean-up tandem immunoassay column by Irina Yu. Goryacheva; Sarah De Saeger; Barbara Delmulle; Marieke Lobeau; Sergei A. Eremin; Ildiko Barna-Vetró; Carlos Van Peteghem (pp. 118-124).
A set-up and simple method based on the clean-up tandem immunoassay approach was developed for the visual detection of two analytes. The method was based on a 1mL column with one clean-up layer and two detection immunolayers. As detection immunolayers CNBr-activated Sepharose 4B with coupled secondary rabbit anti-mouse antibodies was used. Different specific antibodies were coupled to each detection immunolayer. The analysis was realised in a competitive ELISA format with visual detection of the developed colour for each detection immunolayer and took 20min for six sample extracts. The described method was applied to the simultaneous detection of aflatoxin B1 and ochratoxin A in spices with cut-off levels at 5 and 10μgkg−1, respectively. Results were confirmed by LC–MS/MS with immunoaffinity column clean-up.
Keywords: Multiple analysis; Immunoassay; Rapid methods; Mycotoxins; Ochratoxin A; Aflatoxin B1; Spices
Simultaneous non-instrumental detection of aflatoxin B1 and ochratoxin A using a clean-up tandem immunoassay column by Irina Yu. Goryacheva; Sarah De Saeger; Barbara Delmulle; Marieke Lobeau; Sergei A. Eremin; Ildiko Barna-Vetró; Carlos Van Peteghem (pp. 118-124).
A set-up and simple method based on the clean-up tandem immunoassay approach was developed for the visual detection of two analytes. The method was based on a 1mL column with one clean-up layer and two detection immunolayers. As detection immunolayers CNBr-activated Sepharose 4B with coupled secondary rabbit anti-mouse antibodies was used. Different specific antibodies were coupled to each detection immunolayer. The analysis was realised in a competitive ELISA format with visual detection of the developed colour for each detection immunolayer and took 20min for six sample extracts. The described method was applied to the simultaneous detection of aflatoxin B1 and ochratoxin A in spices with cut-off levels at 5 and 10μgkg−1, respectively. Results were confirmed by LC–MS/MS with immunoaffinity column clean-up.
Keywords: Multiple analysis; Immunoassay; Rapid methods; Mycotoxins; Ochratoxin A; Aflatoxin B1; Spices
Characterisation of thorium–ethylenediaminetetraacetic acid and thorium–nitrilotriacetic acid species by electrospray ionisation-mass spectrometry by Andrew J. Cartwright; Colin C. May; Paul J. Worsfold; Miranda J. Keith-Roach (pp. 125-131).
Electrospray ionisation-mass spectrometry (ESI-MS) has been used to investigate the speciation of Th in the presence of two common organic complexing agents found in radioactive wastes, EDTA and NTA. These ligands may enhance radionuclide migration from nuclear wastes and contaminated land, and characterisation of the complexes formed will improve our understanding of their environmental mobility. When acetic acid and ammonia were used to adjust the pH, the dominant Th–EDTA species changed from the mixed ligand [ThEDTAac]− complex to [ThEDTAOH]− and [ThEDTA(OH)2ac]3− as the pH increased, with all species co-existing, to some extent, over the pH range (2.5–10.8). A previously suggested Th–NTA species, [ThNTA2]2−, dominates from pH 6.0–8.5 but at high pH (10.0–10.8) NTA was not able to solubilise Th to a measurable extent. In the presence of both EDTA and NTA, Th formed a mixed ligand complex, [ThEDTANTA]3− which has also been characterised in independent experiments. The identification of the importance of [ThNTA2]2−, [ThEDTANTA]3− and [ThEDTA(OH)2]2− (with an additional acetate ligand) highlights that these species are not included in current speciation databases and thus may impact on predictions of the environmental mobility of Th. ESI-MS has therefore been used to identify and confirm fundamentally important Th complexes. It has proved to be a useful tool for elucidating radionuclide speciation, adding to our knowledge of Th geochemistry and providing a means of critically examining existing stability constant data.
Keywords: Radionuclide; Thorium; Electrospray ionisation-mass spectrometry; Ethylenediaminetetraacetic acid; Nitrilotriacetic acid
Characterisation of thorium–ethylenediaminetetraacetic acid and thorium–nitrilotriacetic acid species by electrospray ionisation-mass spectrometry by Andrew J. Cartwright; Colin C. May; Paul J. Worsfold; Miranda J. Keith-Roach (pp. 125-131).
Electrospray ionisation-mass spectrometry (ESI-MS) has been used to investigate the speciation of Th in the presence of two common organic complexing agents found in radioactive wastes, EDTA and NTA. These ligands may enhance radionuclide migration from nuclear wastes and contaminated land, and characterisation of the complexes formed will improve our understanding of their environmental mobility. When acetic acid and ammonia were used to adjust the pH, the dominant Th–EDTA species changed from the mixed ligand [ThEDTAac]− complex to [ThEDTAOH]− and [ThEDTA(OH)2ac]3− as the pH increased, with all species co-existing, to some extent, over the pH range (2.5–10.8). A previously suggested Th–NTA species, [ThNTA2]2−, dominates from pH 6.0–8.5 but at high pH (10.0–10.8) NTA was not able to solubilise Th to a measurable extent. In the presence of both EDTA and NTA, Th formed a mixed ligand complex, [ThEDTANTA]3− which has also been characterised in independent experiments. The identification of the importance of [ThNTA2]2−, [ThEDTANTA]3− and [ThEDTA(OH)2]2− (with an additional acetate ligand) highlights that these species are not included in current speciation databases and thus may impact on predictions of the environmental mobility of Th. ESI-MS has therefore been used to identify and confirm fundamentally important Th complexes. It has proved to be a useful tool for elucidating radionuclide speciation, adding to our knowledge of Th geochemistry and providing a means of critically examining existing stability constant data.
Keywords: Radionuclide; Thorium; Electrospray ionisation-mass spectrometry; Ethylenediaminetetraacetic acid; Nitrilotriacetic acid
Simultaneous determination of tiopronin andd-penicillamine in human urine by liquid chromatography with ultraviolet detection by Krzysztof Kuśmierek; Edward Bald (pp. 132-137).
d-Penicillamine and tiopronin are drugs widely used for the treatment of many diseases. Because of the relatively high frequency of side effects to these compounds, some of which are dose-related, drug monitoring in urine samples during treatment is advisable. In this paper, we describe a simple method for the determination of tiopronin andd-penicillamine in human urine. The method was based on derivatization with 2-chloro-1-methylquinolinium tetrafluoroborate followed by ion-pairing reversed-phase liquid chromatography separation and ultraviolet-absorbance detection. 2- S-quinolinium derivatives of thiols were detected at 355nm. The derivatization was optimized in terms of pH and time of the reaction. Baseline separation was achieved on an analytical Zorbax SB C-18 (5μm, 150mm×4.6mm) column with a mobile phase consisting of pH 2.0 0.09molL−1 trichloroacetic acid buffer (component A) and acetonitrile (component B) pumped at 1.0mLmin−1. Gradient elution was used: 0–4min, 12% B; 4–8min, 12–40% B; 8–12min, 40–12% B. Thed-penicillamine and tiopronin standards added to the urine show that the response of the detector is linear within the range studied, from 1 to 200μmolL−1 urine. The imprecision ranges for tiopronin andd-penicillamine were within 1.61–8.24% and 2.92–10.60%, respectively. The analytical accuracy for determined compounds was from 97.24 to 109.39%. The lower limits of detection and quantitation were 0.5μmolL−1 and 1.0μmolL−1 urine, respectively. This method can be used for routine clinical monitoring of the title thiol-drugs. Cysteine can be measured concurrently, if needed.
Keywords: d; -Penicillamine; Tiopronin; Cysteine; Liquid chromatography; Derivatization; Urine
Simultaneous determination of tiopronin andd-penicillamine in human urine by liquid chromatography with ultraviolet detection by Krzysztof Kuśmierek; Edward Bald (pp. 132-137).
d-Penicillamine and tiopronin are drugs widely used for the treatment of many diseases. Because of the relatively high frequency of side effects to these compounds, some of which are dose-related, drug monitoring in urine samples during treatment is advisable. In this paper, we describe a simple method for the determination of tiopronin andd-penicillamine in human urine. The method was based on derivatization with 2-chloro-1-methylquinolinium tetrafluoroborate followed by ion-pairing reversed-phase liquid chromatography separation and ultraviolet-absorbance detection. 2- S-quinolinium derivatives of thiols were detected at 355nm. The derivatization was optimized in terms of pH and time of the reaction. Baseline separation was achieved on an analytical Zorbax SB C-18 (5μm, 150mm×4.6mm) column with a mobile phase consisting of pH 2.0 0.09molL−1 trichloroacetic acid buffer (component A) and acetonitrile (component B) pumped at 1.0mLmin−1. Gradient elution was used: 0–4min, 12% B; 4–8min, 12–40% B; 8–12min, 40–12% B. Thed-penicillamine and tiopronin standards added to the urine show that the response of the detector is linear within the range studied, from 1 to 200μmolL−1 urine. The imprecision ranges for tiopronin andd-penicillamine were within 1.61–8.24% and 2.92–10.60%, respectively. The analytical accuracy for determined compounds was from 97.24 to 109.39%. The lower limits of detection and quantitation were 0.5μmolL−1 and 1.0μmolL−1 urine, respectively. This method can be used for routine clinical monitoring of the title thiol-drugs. Cysteine can be measured concurrently, if needed.
Keywords: d; -Penicillamine; Tiopronin; Cysteine; Liquid chromatography; Derivatization; Urine