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Analytical and Bioanalytical Chemistry (v.375, #1)
The Austrian Society of Analytical Chemistry (ASAC) becomes a supporting partner of Analytical and Bioanalytical Chemistry
by Wolfgang F. Lindner (pp. 3-3).
The international patent system, your instrument of revolution
by Patricia E. Eisenhardt (pp. 11-14).
Single-cell analysis by capillary electrophoresis
by Jeffrey N. Stuart; Jonathan V. Sweedler (pp. 28-29).
Analytical characterization of thin carbon films by R. Ohr; C. Schug; M. Wahl; A. Wienss; H. Hilgers; J. Mahrholz; P. Willich; T. Jung (pp. 47-52).
CHx films on silicon substrates deposited by a Mesh Hollow Cathode Process (MHC) were analyzed by various techniques. The films were produced with varying deposition times, resulting in thicknesses ranging from ~2–20 nm. X-Ray Reflectivity (XRR) was used to determine the film thicknesses and the deposition rate. A good correlation of measured XRR thicknesses with SIMS sputter depths down to the film–substrate transition was found.An AFM-based nanoscratching technique was applied to test the wear resistance of the thin overcoats. The MHC films reveal slightly decreasing scratch resistance for reduced film thicknesses, which can be explained by a higher fraction of soft interface zones for thinner films.This is in accordance with Raman spectroscopic measurements in the visible spectral range which were carried out to examine the carbon bonding properties. Combined analysis of G peak position and D/G peak intensity ratio indicates a more graphitic structure for film thicknesses less than 10 nm.
Keywords: Thickness determination Carbon overcoat X-ray reflectivity (XRR) Thin-film analysis Areal storage density
Protein adsorption on surfaces: dynamic contact-angle (DCA) and quartz-crystal microbalance (QCM) measurements by H. Stadler; M. Mondon; C. Ziegler (pp. 53-61).
Adsorption of the protein bovine serum albumin (BSA) on gold has been tested at various concentrations in aqueous solution by dynamic contact-angle analysis (DCA) and quartz-crystal microbalance (QCM) measurements. With the Wilhelmy plate technique advancing and receding contact angles and the corresponding hysteresis were measured and correlated with the hydrophilicity and the homogeneity of the surface. With electrical admittance measurements of a gold-coated piezoelectrical quartz crystal, layer mass and viscoelastic contributions to the resonator's frequency shift during adsorption could be separated. A correlation was found between the adsorbed mass and the homogeneity and hydrophilicity of the adsorbed film.
Keywords: Protein adsorption Dynamic contact-angle analysis Wilhelmy plate method Quartz-crystal microbalance Admittance measurement
A century of progress in the sciences due to atomic weight and isotopic composition measurements by J. de Laeter; H. Peiser (pp. 62-72).
Even before the 20th century, a consistent set of internationally accepted atomic weights was an important objective of the scientific community because of the fundamental importance of these values to science, technology and trade. As the 20th century progressed, physicists, geoscientists, and metrologists collaborated with chemists to revolutionize the science of atomic weights. At the beginning of the century, atomic weights were determined from mass relationships between chemical reactants and products of known stoichiometry. They are now derived from the measured isotopic composition of elements and the atomic masses of the isotopes. Accuracy in measuring atomic weights has improved continually, leading to the revelation of small but significant variations in the isotope abundances of many elements in their normal terrestrial occurrences caused by radioactivity and a variety of physicochemical and biochemical fractionation mechanisms. This atomic-weight variability has now been recognized as providing new scientific insights into and knowledge of the history of materials. Atomic weights, except those of the monoisotopic elements, are thus no longer regarded as "constants of nature". At the beginning of the 20th century, two scales for atomic weights were in common use: that based on the atomic weight of hydrogen being 1 and that based on the atomic weight of oxygen being 16. Atomic weights are now scaled to 12C, which has the value 12 exactly. Accurate atomic weights of silicon, silver, and argon, have enabled the values of the Avogadro, Faraday and Universal Gas constants, respectively, to be established, with consequent effects on other fundamental constants.
Keywords: Atomic weights Isotope fractionation Fundamental constants Isotopic composition IUPAC Mass spectrometry 20th Century
Coupling solid-phase microextraction to liquid chromatography. A review by Carlo G. Zambonin (pp. 73-80).
Solid-phase microextraction (SPME) is a technique for extraction of organic compounds from gaseous, aqueous, and solid matrices. SPME is rapid and simple, ideal for automation and for in situ measurements, and no harmful solvents are needed. The principle of SPME involves equilibration of the analytes between the sample matrix and an organic polymeric phase coated on a fused-silica fiber. SPME is traditionally combined with analysis by gas chromatography (GC) and this combination has proved sensitive, accurate, and precise for quantitative analysis of different classes of volatile compound. More recently SPME has been coupled with liquid chromatography to widen its range of application to non-volatile and thermally unstable compounds also. This article reviews the status of SPME coupled with liquid chromatography. It focuses on different applications of the technique, e.g. environmental samples, biological fluids, and food samples, to show that SPME–HPLC has great potential in the analysis of a wide range of compounds in different matrices.
Keywords: SPME–HPLC Reviews Applications
Modern stationary phases for ion chromatography by J. Weiss; D. Jensen (pp. 81-98).
Due to the better understanding of the processes taking place at the surface of the stationary phases, the number of ion-exchange materials for ion chromatography (IC) has increased tremendously over recent years. As a result, the multitude of commercially available columns today with their different selectivities for anion and cation chromatography is almost confusing. Hence, the aim of this article is to describe the different principles determining selectivity and ion-exchange capacity and to classify the various ion-exchange materials accordingly. To ensure a fair comparison of these columns, the selectivity differences are illustrated by showing separations of standards rather than individual samples.
Keywords: Ion chromatography Stationary phases Support materials Inorganic anions and cations Organic anions and cations
Rapid separation of phenylthiohydantoin amino acids: ambient pressure ion-mobility mass spectrometry (IMMS) by Wes E. Steiner; Brian H. Clowers; Herbert H. Hill (pp. 99-102).
An electrospray ionization (ESI) ambient pressure ion-mobility spectrometer (APIMS) interfaced to an orthogonal reflector time-of-flight mass spectrometer (TOFMS) was evaluated for the first time as a detector for the identification of phenylthiohydantoin (PTH)-derivatized amino acids, the final products in the Edman sequencing process of peptides and proteins. The drift and flight times of the twenty common PTH amino acids were characterized by a well-defined 2-D mobility/mass spectral pattern. The combination of mobility/mass modes of analysis gave rise to a unique trend-line formation for the series of PTH amino acids. In addition, each PTH amino acid had a unique reduced mobility constant Ko, thus enabling the differentiation of all the amino acid derivatives including the PTH-leucine and PTH-isoleucine isomers. More importantly it was shown that it was possible to resolve a complete reference mixture of PTH amino acids in a single experimental run in less than 1 min. Detection limits for the PTH amino acids were found to range from 1.04 to 3.52 ng; indicating that the limits of detection were less than 17.0 pmol for all of the PTH amino acids.
Keywords: Ion-mobility spectrometry Time-of-flight mass spectrometry Phenylthiohydantoin amino acid derivatives Edman sequencing
Carbon nanotube array-based biosensor by Sofia Sotiropoulou; Nikolas A. Chaniotakis (pp. 103-105).
Aligned multi-wall carbon nanotubes (MWNT) grown on platinum substrate are used for the development of an amperometric biosensor. The opening and functionalization by oxidation of the nanotube array allows for the efficient immobilization of the model enzyme, glucose oxidase. The carboxylated open-ends of nanotubes are used for the immobilization of the enzymes, while the platinum substrate provides the direct transduction platform for signal monitoring. It is also shown that carbon nanotubes can play a dual role, both as immobilization matrices and as mediators, allowing for the development of a third generation of biosensor systems, with good overall analytical characteristics.
Keywords: Carbon nanotube Biosensor Array Glucose oxidase
First investigation of an original device dedicated to the determination of gaseous mercury in interstitial air in snow by Aurélien Dommergue; Christophe P. Ferrari; Claude F. Boutron (pp. 106-111).
The GAMAS (gaseous mercury in interstitial air in snow) instrument developed in our laboratory is a new device devoted to sampling and determination of gaseous mercury concentration in interstitial air in snow. Sampling probes inserted in the snowpack, coupled with a Gardis mercury vapour analyser, provide reliable and original data of vertical profiles of both snow temperature and gaseous mercury concentration at several depths in a snow mantle. This instrument has been tested successfully in Station Nord in Greenland in February–March 2002. A description of this instrument, of the sampling area and its setting up is presented with precise details. Illustrations of the first investigations are given showing a rapid decrease of gaseous mercury concentration simultaneously with depth. A concentration of 0.10 ng/m3 is reached at 120 cm depth. It may be the result of fast oxidation processes occurring within the snowpack.Gaseous mercury behaviour in the snowpack is a central parameter to elucidate the fate of deposited mercury after mercury depletion events in polar regions. With our new device, we have now the opportunity to determine this key parameter.
Keywords: Gaseous mercury Interstitial air in snow New instrument Air/snow exchanges Arctic
The reverse auto-compression system: a new type of column for preparative liquid chromatography by François Dardoize; Gilles Clodic; Jean Chevalet (pp. 112-119).
Axial compression of the stationary phase is an easy technique for packing preparative liquid chromatography columns. However, the compression piston often needs an important external device to move the external jack. A new type of column is described which uses an auto-compression system to move the piston and compress the packing material. The system is fitted with a new annular injector which is known to reduce the peak tailing. The results of the tests demonstrate the ease of use of this column, its efficiency and stability.
Keywords: Preparative liquid chromatography Annular injection Auto compression Phthalic acid esters
Multi-analyte analysis system using an antibody-based biochip by Maria Moreno-Bondi; Jean Alarie; Tuan Vo-Dinh (pp. 120-124).
A multi-analyte detection system using a unique antibody (Ab) biochip is described. The Ab-based biochip, also referred to as the protein biochip, uses a sensor array based on a complementary metal oxide silicon (CMOS) integrated circuit. The Ab-biochip has a sampling platform of four-by-four microarrays of antibodies deposited onto a Nylon membrane substrate. The micro-arrayed antibodies can be interrogated simultaneously or sequentially using the biochip sensing array detector with the use of a diffractive optical element illuminating each antibody spot individually. The usefulness of the Ab biochip is illustrated by the measurements of immunoglogulin G (IgG) used as the model analyte system. The detection limit for Cy5-labeled IgG molecules was 13 pg.
Keywords: Immunoassay Antibody array Biochip Protein biochip Multi-analyte
A capillary-based amperometric flow immunoassay for 2,4,6-trichlorophenol by Catalin Nistor; Jenny Emnéus (pp. 125-132).
This paper describes the development of two different capillary-based heterogeneous competitive flow immunoassay formats (capillary flow injection immunoassay (CFIIA) and capillary sequential injection immunoassay (CSIIA)) for the determination of 2,4,6-trichlorophenol (2,4,6-TCP). The assays are based on the competition between the analyte and an analyte derivative labelled with the enzyme β-galactosidase, for an anti-TCP antibody, followed by the injection of the mixture at equilibrium into a flow stream, where separation between the fractions bound and unbound to the antibody is performed in a glass capillary containing immobilised protein A. The antibody-tracer fraction retained inside the protein A capillary was measured by injection of 4-aminophenyl-β-D-galactoside (4-APG), followed by amperometric detection of the enzymatically generated 4-aminophenol (4-AP), leading to a negative correlation between the signal and the analyte concentration.The two immunoassay formats were compared in terms of sensitivity and speed, giving IC50 values of 1.41±0.03 and 1.64±0.07 µg L–1, detection limits of 0.2 and 0.4 µg L–1, and sample throughputs of 6 and 4 h–1 for the CFIIA and CSIIA system, respectively.The influence of different interfering chlorophenolic compounds in the assay was minor, with only one exception (i.e. 2,4-dichlorophenol). In addition, different water matrices were tested (surface, tap, and rain water), showing that the matrix influence was negligible, except for rainwater, which resulted in a 30% increase in sensitivity. As a conclusion, the assay is suitable for the fast screening of TCP present at low concentration levels in water samples.
Keywords: Flow immunoassay Protein A Trichlorophenol Galactosidase label
Hydrolysis of proteins with methanesulfonic acid for improved HPLC-ICP-MS determination of seleno-methionine in yeast and nuts by Katarzyna Wrobel; Sasi S. Kannamkumarath; Kazimierz Wrobel; Joseph A. Caruso (pp. 133-138).
In this work, the use of methanesulfonic acid for protein hydrolysis is proposed for evaluation of Se-methionine in yeast, Brazil nuts, and possibly other selenium-rich biological samples. The hydrolysis was carried out by heating the sample with 4 mol L–1 acid at reflux for 8 h. Two chromatographic techniques (size-exclusion and ion-pairing) coupled with ICP-MS detection were used to compare the release of Se-methionine from proteins by enzymatic (proteinase K, protease XIV) and acid hydrolyses. A more efficient liberation of Se-methionine was observed by acid hydrolysis. For quantification, the sample extracts were introduced onto a C8 Alltima column, and the separation was achieved with a mobile phase containing 5 mmol L–1 hexanesulfonic acid in citrate buffer (pH 4.5)/methanol (95:5). The results obtained by standard addition showed 816±17 µg g–1 and 36.2±1.5 µg g–1 of selenium in the form of Se-methionine in yeast and nuts, respectively (65% and 75% of total selenium).
Keywords: Se-methionine Yeast Brazil nuts Hydrolysis HPLC-ICP-MS
Simultaneous determination of arsenic(III) and arsenic(V) by flow injection–inductively coupled plasma–atomic emission spectrometry (ICP-AES) with ultrasonic nebulization by Sathrugnan Karthikeyan; Shizuko Hirata (pp. 139-144).
A dual-column protocol for the sequential determination of As(III) and As(V) is described using inductively coupled plasma–atomic emission spectrometry (ICP-AES) with ultrasonic nebulization (USN). This procedure employed a 16-way valve containing two different homemade mini columns for selective preconcentration of As(III) and As(V). One column was filled with Muromac A-1, which selectively preconcentrated As(III) at pH 3 after complexation with ammonium pyrrolidine dithiocarbamate (APDC, 0.05%). The effluent of the first column was then passed through the second column, which was filled with an anion-exchange resin to collect As(V). By using 0.6 M sodium hydroxide, both species were eluted sequentially and measured by ICP-AES. Enrichment factors of 136 (17 for micro column ×8 for USN) for As(V) and 160 (20 for micro column ×8 for USN) for As(III) were achieved with 4 min preconcentration. With the proposed procedure, the detection limits were calculated to be 0.7 µg L–1 for As(V) and 0.8 µg L–1 for As(III) based on (3σ) blank determination (N=10). The relative standard deviations for 20 µg L–1 of As(V) and As(III) were 5.8% and 6.5%, respectively. The recovery for spiked water samples was in the range of 85–112%.
Keywords: Arsenic(III) Arsenic(V) ICP-AES ultrasonic nebulization Column preconcentration Fresh waters
Identification and quantification of metallothionein isoforms and superoxide dismutase in spiked liver extracts using HPLC-ESI-MS offline coupling and HPLC-ICP-MS online coupling by V. Nischwitz; B. Michalke; A. Kettrup (pp. 145-156).
A two-dimensional chromatographic method for the characterization of metallothionein isoforms (MT) and superoxide dismutase (SOD) in spiked liver extracts was developed for the optimization of extraction procedures from liver samples. Element-specific detection (ICP-MS) and molecule-specific detection (ESI-MS) were applied for maximum species information. A special focus was laid on the quantitative data evaluation (species stoichiometry, calibration with and without matrix, recovery), which is neglected in most MT/SOD publications with hyphenated techniques. Linearity, precision (residual standard deviation of calibration curves <10%), and detection limits (<0.6 mg L–1 for MT isoforms and 13 mg L–1 for SOD) prove the suitability of the method for quantification. An alternative quantification is proposed for the extension towards other lesser or even unknown trace element species, especially the native porcine MT and SOD.
Keywords: Speciation Liver Metallothionein Superoxide dismutase
Enantiomeric purity determination of ketoprofen by capillary electrophoresis: development and validation of the method by Marcelo Blanco; Josep González; Ester Torras; Ismael Valverde (pp. 157-163).
A simple, fast capillary electrophoresis method for determining the total ketoprofen content in an oral pharmaceutical formulation is proposed. The addition of 75 mM of heptakis(tri-O-methyl)-β-cyclodextrin to the background electrolyte allows the quantitation of the enantiomeric impurity of (R)-(–)-ketoprofen contained in the formulation. A relative limit of detection is proposed as a measure of the lowest detectable enantiomeric impurity and the results show that the method can detect the minor enantiomer at levels as low as 0.04% in (S)-(+)-ketoprofen. The chiral method was validated following ICH recommendations and the quality parameters obtained show the suitability of the proposed method. The analysis of samples examined during the course of a stability study under chiral and achiral conditions revealed that the total ketoprofen content did not change significantly with time and the enantiomeric impurity range was 0.1–0.4%.
Keywords: Chiral CE Enantiomeric purity determination Ketoprofen Cyclodextrins Stability study
Voltammetric determination of thiodiglycolic acid in urine by Zdeňka Dlasková; Tomáš Navrátil; Michael Heyrovský; Daniela Pelclová; Ladislav Novotný (pp. 164-168).
In urine the level of thiodiglycolic acid (TDGA) is a sensitive indicator of exposure of the human organism to some physiologically active or toxic substances, gases and vapors. The determination of TDGA by use of a voltammetric method based on electroreduction of TDGA in acidic solution at the hanging mercury drop electrode has been developed and practically tested. In order to eliminate the matrix effect of urine, prior to voltammetric measurement the samples are eluted from a small column of PVC powder. The method is simple, low cost, rapid and sensitive, appropriate for the needs of occupational medicine.
Keywords: Urine Thiodiglycolic acid Metabolic noxae Voltammetry Mercury electrode
Enhanced selectivity and sensitivity for inorganic anions using an ion-pairing reagent and sample stacking in capillary zone electrophoresis with direct UV detection by ZuLiang Chen; Gary Owens; Ravendra Naidu (pp. 182-187).
In this paper, the use of an ion-pairing reagent to improve the separation selectivity of inorganic anions in CZE was demonstrated by the addition of tetramethylammonium hydroxide (TMAOH) to the electrolyte. The separation of inorganic anions (Cl–, I–, Br–, NO2 –, NO3 – and SCN–) was performed using co-electroosmotic flow (EOF) with direct UV detection at 185 nm. The parameters affecting the mobility of the tested anions and the EOF such as the electrolyte pH and concentration of TMAOH in the electrolyte were examined to optimise the separation conditions. In addition, sample-stacking techniques were investigated to improve detection sensitivity. Detection sensitivities were improved 5–13-fold using electrokinetic sample stacking. The detection limits ranged from 1–3 µmol L–1. Finally, the proposed method was used for the separation of anions in groundwaters.
Keywords: Anions CZE Selectivity and sensitivity Ion-pairing reagent Groundwater.
Strategies for detection of the ecotoxicological risks of degradation metabolites
by Ralph G. Weyandt; Julien Pressel (pp. 188-189).