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Analytical and Bioanalytical Chemistry (v.386, #2)

Politics in organisations: how to survive and thrive by Sara Shinton (pp. 197-199).

started her professional life as a chemist, following her first degree in Chemical and Analytical Science with a PhD in Physical Chemistry. After a brief period in post-doctoral research, she discovered an interest in transferable skills whilst teaching undergraduate chemists communication skills. After retraining as a university careers adviser in 2000, she founded a company [ http://www.shintonconsulting.com ] and now delivers careers guidance and skills training to academic researchers and scientists across the UK and Europe.

Vladimir M. Mirsky (Ed.): Ultrathin Electrochemical Chemo- and Biosensors: Technology and Performance by Frieder W. Scheller (pp. 200-201).

M. Hamacher, K. Marcus, K. Stühler, A. van Hall, B. Warscheid, H.E. Meyer (Eds.): Proteomics in Drug Research by Wolf D. Lehmann (pp. 202-203).

Peter E. Wall: Thin-Layer Chromatography. A modern practical approach by Paweł K. Zarzycki (pp. 204-205).

Homogeneous indirect fluorescence quenching immunoassay for the determination of low molecular weight substances by F. Sellrie; A. Warsinke; B. Micheel (pp. 206-210).

This paper describes the principle of a homogeneous indirect fluorescence quenching immunoassay that uses monoclonal antibodies. It is a carrier-free assay system that is performed completely in solution. The assay system was established for the determination of a low molecular weight substance (hapten), the herbicide diuron, used as a model analyte. A fluorescein–monuron conjugate together with a fluorescence-quenching monoclonal anti-fluorescein antibody and an anti-analyte antibody (here an anti-diuron/monuron monoclonal antibody) were used as central components of the assay. The fluorescein–monuron conjugate can be bound either by the anti-fluorescein monoclonal antibody or by the anti-diuron/monuron monoclonal antibody. Due to steric hindrance, binding of both antibodies to the conjugate was not possible at the same time. By selecting the antibody concentrations appropriately, a dynamic equilibrium can be established that permits the preferential binding of the anti-diuron/monuron antibody to the conjugate, which allows the fluorescein in the conjugate to fluoresce. This equilibrium can be easily altered by adding free analyte (diuron), which competes with the conjugate to bind to the anti-diuron/monuron antibody. A reduction of anti-diuron/monuron antibody binding to the conjugate results in an increase in the binding of the anti-fluorescein antibody, which leads to a decrease in the fluorescence of the conjugate. The fluorescence is therefore a direct indicator of the state of equilibrium of the system and thus also the presence of free unconjugated analyte. The determination of an analyte based on this test principle does not require any washing steps. After the test components are mixed, the dynamic equilibrium is rapidly reached and the results can be obtained in less than 5 min by measuring the fluorescence of the fluorescein. We used this test principle for the determination of diuron, which was demonstrated for concentrations of ∼5 nM.

Keywords: Homogeneous immunoassay; Fluorescence quenching; Indirect fluorescence quenching immunoassay; Fluorescein; Diuron

Preparation and evaluation of spore-specific affinity-augmented bio-imprinted beads by Scott D. Harvey; Gary M. Mong; Richard M. Ozanich; Jeffrey S. Mclean; Shannon M. Goodwin; Nancy B. Valentine; Jim K. Fredrickson (pp. 211-219).

A novel, affinity-augmented, bacterial spore-imprinted, bead material was synthesized, based on a procedure developed for vegetative bacteria. The imprinted beads were intended as a front-end spore capture/concentration stage of an integrated biological detection system. Our approach involved embedding bead surfaces with Bacillus thuringiensis kurstaki (Bt) spores (as a surrogate for Bacillus anthracis) during synthesis. Subsequent steps involved lithographic deactivation using a perfluoroether; spore removal to create imprint sites; and coating imprints with the lectin, concanavalin A, to provide general affinity. The synthesis of the intended material with the desired imprints was verified by scanning electron and confocal laser-scanning microscopy. The material was evaluated using spore-binding assays with either Bt or Bacillus subtilis (Bs) spores. The binding assays indicated strong spore-binding capability and a robust imprinting effect that accounted for 25% additional binding over non-imprinted controls. The binding assay results also indicated that further refinement of the surface deactivation procedure would enhance the performance of the imprinted substrate.

Keywords: Bio-imprinted beads; Selective spore capture/concentration; Analysis of biological pathogens

l-Glutamate biosensor for estimation of the taste of tomato specimens by Rasa Pauliukaite; Gleb Zhylyak; Daniel Citterio; Ursula E. Spichiger-Keller (pp. 220-227).

An amperometric biosensor has been developed for measurement of Umami, or the taste based on the amount of l-glutamate, in tomato foods. The biosensor is based on an enzyme-mediator system in which l-glutamate oxidase is used for biochemical oxidation of l-glutamate and a tetrafulvalene-tetracyanoquinodimethane (TTF-TCNQ) paste, prepared from the mixture of TTF-TCNQ salt, graphite powder, and silicone oil, serves as the mediator. The limit of detection, calculated by use of a four-parameter logistic model, was 0.05 mmol L⁻¹, and the limit of quantification was 0.15 mmol L⁻¹. The correlation coefficient (R ²) was 0.990 and the relative standard deviation was no more than 1% (n=5). The response time (τ ₉₅) was 20–50 s, depending on concentration. The repeatability of the sensor was better than 5% (n=10). The sensor developed was stable for more than ten days.

Keywords: Amperometric biosensors; Umami; l-Glutamate determination; l-Glutamate oxidase; TTF-TCNQ

Amperometric determination of bovine insulin based on synergic action of carbon nanotubes and cobalt hexacyanoferrate nanoparticles stabilized by EDTA by Fengli Qu; Minghui Yang; Yashuang Lu; Guoli Shen; Ruqin Yu (pp. 228-234).

A simple approach is proposed for the synthesis of cobalt hexacyanoferrate nanoparticles (CoNPs) with uniform shape and size controlled by ethylene diamine tetraacetic acid (EDTA) as a stabilizer. A sensitive amperometric biosensor for insulin has been prepared using glassy carbon electrodes by solubilization of carbon nanotubes (CNTs) in chitosan (CHIT) together with CoNPs synthesized by the new methodology. The CoNP-CNT-CHIT organic–inorganic system exerts a synergistic effect, resulting in the remarkably enhanced insulin currents owing to the superior electron-transfer ability of CNTs and the excellent reversible redox centers of CoNPs. High-resolution transmission electron microscopy (HRTEM) was used to provide closer inspection of the CoNPs. The effects of alkali metal cations and the concentrations of CNTs and CoNPs on the voltammetric behavior of the film-modified electrode were also investigated. In pH 6.98 phosphate buffer (PB) at +0.7 V (vs. SCE) the insulin biosensor exhibits a linear response range of 0.1–3 μM with a correlation coefficient of 0.98, and the detection limit (S/N=3) is determined to be 40 nM, the stability of the biosensor was tested and found satisfactory. There is great promise for in vivo measurements of this important hormone.

Keywords: Cobalt hexacyanoferrate; Carbon nanotubes; Insulin; Chitosan

Validated multi-component CZE-UV procedure for the quantification of human hemorphin LVV-H7 in plasma stability studies by Harald John; Stefanie Schulz; Wolf-Georg Forssmann (pp. 235-243).

The human hemorphin LVV-H7 is an endogenous cleavage product of the hemoglobin β, γ, ε or δ chain exhibiting potential pharmaceutical relevance for blood pressure regulation, the treatment of Alzheimer’s disease or learning deficiencies. Here we present the development of a multi-component capillary zone electrophoretic method (CZE-UV), allowing the simultaneous quantification of LVV-H7 and four N-terminal degradation products generated in EDTA plasma. Hemorphins in the supernatant of precipitated plasma samples are quantified by external calibration. Validation of the procedure oriented towards international pharmaceutical guidelines and demonstrated excellent linearity ( r ² ≥0.999), good precision (repeatability and reproducibility below 11%), accuracy (−8.4%–4%), ruggedness and an appropriate lower limit of quantification (LLOQ 1.0 μg mL⁻¹). This procedure was applied to stability studies of LVV-H7 in human EDTA plasma attended by profiling metabolites using qualitative MALDI-TOF MS analysis. We detected the activity of a soluble plasma form of aminopeptidase M causing successive N-terminal truncation. This is the first time that LVV-H7 degradation as well as its metabolite production have systematically been monitored by a quantitative CZE-UV procedure, underlining the growing importance of such techniques in peptide analysis. In addition, our results give useful hints for future drug development of LVV-H7.

Keywords: Aminopeptidase M; CZE-UV; Hemorphins; LVV-H7; Peptide quantification

Fluorometry of hydrogen peroxide using oxidative decomposition of folic acid by Kazutaka Hirakawa (pp. 244-248).

Hydrogen peroxide (H₂O₂) is one of the most important reactive oxygen species. In the present study, a fluorometry method for detecting H₂O₂ utilizing folic acid was evaluated. Folic acid was decomposed by H₂O₂ in the presence of Cu(II) into pterine-6-carboxylic acid, leading to strong fluorescence enhancement. In the absence of the metal ion, superoxide and H₂O₂ could not decompose folic acid. Also, H₂O₂ plus sodium hypochlorite (a source of singlet oxygen) could not induce fluorescence enhancement. These results demonstrate that H₂O₂ can be selectively detected using folic acid plus Cu(II). The limit of detection (LOD; at S/N=3) for H₂O₂ is 0.5 μM. This method based on the fluorescence enhancement of folic acid was applied in order to determine small amounts of H₂O₂ generated through the autooxidation of semicarbazide (generation rate: ∼0.01 μM min⁻¹), a carcinogenic compound.

Keywords: Hydrogen peroxide; Reactive oxygen species; Fluorometry; Folic acid; Copper(II) ion

In situ characterisation of a microorganism surface by Raman microspectroscopy: the shell of Ascaris eggs by Fabienne Quilès; Jean-Yves Balandier; Sandrine Capizzi-Banas (pp. 249-255).

Intestinal nematodes are very common human parasites and a single species, Ascaris lumbricoïdes, is estimated to infect a quarter of the world’s population. A sticky external layer covers their eggs. This work shows that Raman vibrational confocal spectroscopy is able to give information on the biochemical composition of the shell of Ascaris eggs. The biochemical localised characterisation of Ascaris eggs was performed directly on the eggs in their aqueous environment. The studied parasites came from two origins: dissections of adult females and extractions from biosolid sludges. The presence of mucopolysaccharides, proteins and chitin in the shell was demonstrated. The presence of ascaroside compounds was shown particularly via the narrow and intense bands from the organised long CH₂ chains. To the best of our knowledge, this is the first time that the latter have been observed in Raman vibrational spectra of microorganisms. Hydration of the shell was different depending on the intensity of the colour of the sludge eggs. Knowledge of the biochemical structural properties of egg surfaces would be useful to understand the egg adhesion phenomena on vegetables contaminated by reused wastewater.

Keywords: Ascaris ; Nematodes; Raman spectroscopy; Mucopolysaccharide; Ascarosides; Surface

Optimization of solid-phase microextraction procedures for the determination of tricyclic antidepressants and anticonvulsants in plasma samples by liquid chromatography by Marcelo Delmar Cantú; Daniel Rodrigo Toso; Cristina Alves Lacerda; Fernando Mauro Lanças; Emanuel Carrilho; Maria Eugênia Costa Queiroz (pp. 256-263).

Simple, sensitive, and reproducible off-line solid-phase microextraction and liquid chromatography (SPME/LC) methods are described for the determination of seven anticonvulsants and tricyclic antidepressants in human plasma. Factorial design and simplex methodology were applied in the optimization of the SPME procedure for tricyclic antidepressants analyses. Important factors in the SPME efficiency are discussed, such as the fiber coatings (both lab-made and commercial), extraction time, pH, ionic strength, influence of plasma proteins, and desorption conditions. The development of the lab-made fiber coatings, namely, octadecylsilane, aminosilane, and polyurethane, are further described and applied to anticonvulsants analyses. The investigated plasmatic range for the evaluated anticonvulsants, using CW-TPR fiber, were the following: phenylethylmalonamide (3.00–40.0 μg mL⁻¹), phenobarbital (5.00–40.0 μg mL⁻¹), primidone (3.00–40.0 μg mL⁻¹), carbamazepine and carbamazepine-epoxide (2.00–24.0 μg mL⁻¹), phenytoin (2.00–40.0 μg mL⁻¹), and lamotrigine (0.50–12.0 μg mL⁻¹). The antidepressants’ linear plasmatic concentration ranged from 75.0 to 500 ng mL⁻¹ for imipramine, amitriptyline, and desipramine, and from 50.0 to 500 ng mL⁻¹ for nortriptyline, being in all cases, the limit of quantification represented by the lowest value. The precision (interassays) for all investigated drugs in plasma sample spiked with different concentrations of each analyte and submitted to the described procedures were lower than 15%. The off-line SPME/LC methodologies developed allow anticonvulsants and antidepressants analyses from therapeutic to toxic levels for therapeutic drug monitoring.

Keywords: Solid-phase microextraction; Tricyclic antidepressants; Anticonvulsants; Factorial design; Plasma samples; Bioanalytical methods

Screening and analysis of an antineoplastic compound in Rhizoma Chuanxiong by means of in vitro metabolism and HPLC-MS by Liang Kong; Zhiyuan Yu; Yongming Bao; Xingye Su; Hanfa Zou; Xin Li (pp. 264-274).

A new screening and analysis method that combines in vitro metabolism with high-performance liquid chromatography-mass spectrometry (HPLC-MS) was developed for the screening and analysis of an antineoplastic compound, coniferyl ferulate, which is present in the rhizome of Rhizoma Chuanxiong. Infrared (IR), ultraviolet visible spectroscopy (UV-Vis), nuclear magnetic resonance (NMR) and element analysis were used to identify the molecular structure of coniferyl ferulate. The quantitative analysis of coniferyl ferulate in different extracts of Rhizoma Chuanxiong was carried out, and the metabolism of coniferyl ferulate was investigated by in vitro incubation with rat liver homogenate. The metabolite of coniferyl ferulate, ferulic acid ethyl ester, was identified by HPLC-MS, UV-Vis and IR. In addition, antineoplastic activities of coniferyl ferulate and ferulic acid ethyl ester were detected by the MTT assay. The observed inhibition rate of coniferyl ferulate on the activity of HeLa cells was over 80% at 5.4 ng μl⁻¹. However, its metabolite, ferulic acid ethyl ester, showed no antineoplastic activity in vitro.

Keywords: Coniferyl ferulate; Ferulic acid ethyl ester; HPLC-MS; Rhizoma chuanxiong ; Traditional Chinese medicine

Validated HPLC–MS–MS method for simultaneous determination of atorvastatin and 2-hydroxyatorvastatin in human plasma—pharmacokinetic study by V. Bořek-Dohalský; J. Huclová; B. Barrett; B. Němec; I. Ulč; I. Jelínek (pp. 275-285).

Cholesterol-reducing statin drugs are the most frequently prescribed agents for reducing morbidity and mortality related to coronary heart disease. In this publication a validated, highly sensitive, and selective isocratic HPLC method is reported for quantitative determination of the major statin drug atorvastatin (ATV) and its metabolite 2-hydroxyatorvastatin (HATV). Detection was performed with an electrospray ionization triple-quadrupole mass spectrometer equipped with an ESI interface operating in positive-ionization mode. Multiple reaction monitoring (MRM) was used for MS–MS detection. The calibration plot was linear in the concentration range 0.10–40.00 ng mL⁻¹ for both ATV and HATV. Inter-day and intra-day precision and accuracy of the proposed method were characterized by measurement of relative standard deviation (RSD) and percentage deviation, respectively; both were less than 8% for both analytes. The limit of quantitation was 0.02 ng mL⁻¹ for ATV and 0.07 ng mL⁻¹ for HATV. The method was used for pharmacokinetic study of ATV and HATV. Pharmacokinetic data for all analytes are also reported.

Keywords: Atorvastatin; HPLC; MS; Plasma; Pharmacokinetic study

A new approach to non-destructive analysis of biofilms by confocal Raman microscopy by Ralf Pätzold; Maike Keuntje; Angelika Anders-von Ahlften (pp. 286-292).

Confocal Raman microscopy (CRM) of biofilms enables one to determine the distribution of different microorganisms and other substances inside physiological intact microbial communities. These biofilms are of outstanding interest for biological wastewater treatment. In contrast to invasive techniques, such as fluorescent in situ hybridization (FISH), we were able to identify anaerobically ammonium-oxidising (anammox) bacteria without pretreatment processes of the samples just by its Raman vibrational signature. The presented results provide new insights into the complex interactions of different organisms in microbial communities without interfering with them.

Keywords: Confocal Raman microscopy; Biofilm; Microbial communities

Analysis of odorous trichlorobromophenols in water by in-sample derivatization/solid-phase microextraction GC/MS by Alfredo Díaz; Francesc Ventura; Maria Teresa Galceran (pp. 293-298).

The simultaneous determination of several odorous trichlorobromophenols in water has been carried out by an in-sample derivatization headspace solid-phase microextraction method (HS-SPME).The analytical procedure involved their derivatization to methyl ethers with dimethyl sulfate/NaOH and further HS-SPME and gas chromatography-mass spectrometry (GC/MS) determination. Parameters affecting both the derivatization efficiency and headspace SPME procedures, such as the selection of the SPME fiber coating, derivatization–extraction time and temperature, were studied. The commercially available polydimethylsiloxane (PDMS) 100 μm and Carboxen-polydimethylsiloxane-divinylbenzene (CAR-PDMS-DVB) fibers appeared to be the most suitable for the simultaneous determination of these compounds. The precision of the HS-SPME/GC/MS method gave good relative standard deviations (RSDs) run-to-run between 9% and 19% for most of them, except for 2,5-diCl-6-Br-phenol, 2,6-diCl-3-Br-phenol and-2,3,6-triBr-phenol (22%, 25% and 23%, respectively). The method was linear over two orders of magnitude, and detection limits were compound dependent but ranged from 0.22 ng/l to 0.95 ng/l. The results obtained for water samples using the proposed SPME procedure were compared with those found with the EPA 625 method, and good agreement was achieved. Therefore, the in-sample derivatization HS-SPME/GC/MS procedure here proposed is a suitable method for the simultaneous determination of odorous trichlorobromophenols in water.

Keywords: Water; Separations/instrumentation; GC; Organic compounds/trace organic compounds

A viologen-based UV indicator and dosimeter by Andrew Mills; Michael McFarlane; Stefan Schneider (pp. 299-305).

A UV indicator/dosimeter based on benzyl viologen (BV²⁺) encapsulated in polyvinyl alcohol (PVA) is described. Upon exposure to UV light, the BV²⁺/PVA film turns a striking purple colour due to the formation of the cation radical, BV^•+. The usual oxygen sensitivity of BV^•+ is significantly reduced due to the very low oxygen permeability of the encapsulating polymer, PVA. Exposure of a typical BV²⁺/PVA film, for a set amount of time, to UVB light with different UV indices produces different levels of BV^•+, as measured by the absorbance of the film at 550 nm. A plot of the change in absorbance at this wavelength, ΔAbs(550), as a function of UV index, UVI, produces a linear calibration curve which allows the film to be used as a UVB indicator, and a similar procedure could be employed to allow it to be used as a solar UVI indicator. A typical BV²⁺/PVA film generates a significant, semi-permanent (stable for >24 h) saturated purple colour (absorbance ~0.8–0.9) upon exposure to sunlight equivalent to a minimal erythemal dose associated with Caucasian skin, i.e. skin type II. The current drawbacks of the film and the possible future use of the BV²⁺/PVA film as a personal solar UV dosimeter for all skin types are briefly discussed.

Keywords: UV dosimeter; UV indicator; Methyl viologen; Photoreduction

Quantification of abscisic acid in grapevine leaf (Vitis vinifera) by isotope-dilution liquid chromatography–mass spectrometry by Francisca Vilaró; Anna Canela-Xandri; Ramon Canela (pp. 306-312).

A specific, sensitive, precise, and accurate method for the determination of abscisic acid (ABA) in grapevine leaf tissues is described. The method employs high-performance liquid chromatography and electrospray ionization–mass spectrometry (LC-ESI-MS) in selected ion monitoring mode (SIM) to analyze ABA using a stable isotope-labeled ABA as an internal standard. Absolute recoveries ranged from 72% to 79% using methanol/water pH 5.5 (50:50 v/v) as an extraction solvent. The best efficiency was obtained when the chromatographic separation was carried out by using a porous graphitic carbon (PGC) column. The statistical evaluation of the method was satisfactory in the work range. A relative standard deviation (RDS) of < 5.5% and < 6.0% was obtained for intra-batch and inter-batch comparisons, respectively. As for accuracy, the relative error (%Er) was between −2.7 and 4.3%, and the relative recovery ranged from 95% to 107%.

Keywords: Abscisic acid; Isotopically labeled internal standard; LC-ESI-MS; Vitis vinifera ; Grapevine leaf

Voltammetric procedure for trace metal analysis in polluted natural waters using homemade bare gold-disk microelectrodes by C. Garnier; L. Lesven; G. Billon; A. Magnier; Ø. Mikkelsen; I. Pižeta (pp. 313-323).

Voltammetric procedures for trace metals analysis in polluted natural waters using homemade bare gold-disk microelectrodes of 25- and 125-μm diameters have been determined. In filtered seawater samples, square wave anodic stripping voltammetry (SWASV) with a frequency of 25 Hz is applied for analysis, whereas in unfiltered contaminated river samples, differential pulse anodic stripping voltammetry (DPASV) gave more reliable results. The peak potentials of the determined trace metals are shifted to more positive values compared to mercury drop or mercury-coated electrodes, with Zn always displaying 2 peaks, and Pb and Cd inversing their positions. For a deposition step of 120 s at −1.1 V, without stirring, the 25-μm gold-disk microelectrode has a linear response for Cd, Cu, Mn, Pb and Zn from 0.2 μg L⁻¹ (1 μg L⁻¹ for Mn) to 20 μg L⁻¹ (30 μg L⁻¹ for Zn, Pb and 80 μg L⁻¹ for Mn). Under the same analytical conditions, the 125-μm gold-disk microelectrode shows linear behaviour for Cd, Cu, Pb and Zn from 1 μg L⁻¹ (5 μg L⁻¹ for Cd) to 100 μg L⁻¹ (200 μg L⁻¹ for Pb). The sensitivity of the 25-μm electrode varied for different analytes from 0.23 (±0.5%, Mn) to 4.83 (±0.9%, Pb) nA L μmol⁻¹, and sensitivity of the 125-μm electrode varied from 1.48 (±0.7%, Zn) to 58.53 (±1.1%, Pb nA L μmol⁻¹. These microelectrodes have been validated for natural sample analysis by use in an on-site system to monitor Cu, Pb and Zn labile concentrations in the Deûle River (France), polluted by industrial activities. First results obtained on sediment core issued from the same location have shown the ability of this type of microelectrode for in situ measurements of Pb and Mn concentrations in anoxic sediments.

Keywords: Voltammetry; Bare gold microelectrode; Environmental monitoring; Trace metals

Determination of semi-volatile priority pollutants in landfill leachates and sediments using microwave-assisted headspace solid-phase microextraction by Paulo Herbert; Ana L. Silva; Maria J. João; Lúcia Santos; Arminda Alves (pp. 324-331).

The present work was focused on the development of a simple method aimed at the determination of 12 polycyclic aromatic hydrocarbons (PAHs) and 15 polychlorinated biphenyls (PCBs) in landfill leachates and sediments by adapting a domestic microwave oven to perform microwave-assisted headspace solid-phase microextraction (MA-HS-SPME) followed by gas chromatographic separation and tandem mass spectrometric detection. Good linearity was observed within the concentration range studied; detection limits ranged from 0.1 ng/l to 7 ng/l for PCBs and from 5 ng/l to 926 ng/l for PAHs. Concerning precision, the relative standard deviations obtained were, on average for the leachate and sediment samples analysed, 18% for PCBs and 20% for PAHs. Average recovery values were 37% and 76% for PCBs, and 58% and 48% for PAHs, respectively, for the leachate and reference sediment studied. The method allows the determination of PAHs and PCBs in landfill leachates and sediments, avoiding clean-up steps and the consumption of organic solvents.

Keywords: Solid-phase microextraction; Microwave-assisted extraction; Polychlorinated biphenyls; Polycyclic aromatic hydrocarbons; Landfill leachates; Sediments

Optimisation of solid-phase microextraction coupled to HPLC-UV for the determination of organochlorine pesticides and their metabolites in environmental liquid samples by M. E. Torres Padrón; Z. Sosa Ferrera; J. J. Santana Rodríguez (pp. 332-340).

A solid-phase microextraction (SPME) procedure using two commercial fibers coupled with high-performance liquid chromatography (HPLC) is presented for the extraction and determination of organochlorine pesticides in water samples. We have evaluated the extraction efficiency of this kind of compound using two different fibers: 60-μm polydimethylsiloxane–divinylbenzene (PDMS-DVB) and Carbowax/TPR-100 (CW/TPR). Parameters involved in the extraction and desorption procedures (e.g. extraction time, ionic strength, extraction temperature, desorption and soaking time) were studied and optimized to achieve the maximum efficiency. Results indicate that both PDMS-DVB and CW/TPR fibers are suitable for the extraction of this type of compound, and a simple calibration curve method based on simple aqueous standards can be used. All the correlation coefficients were better than 0.9950, and the RSDs ranged from 7% to 13% for 60-μm PDMS-DVB fiber and from 3% to 10% for CW/TPR fiber. Optimized procedures were applied to the determination of a mixture of six organochlorine pesticides in environmental liquid samples (sea, sewage and ground waters), employing HPLC with UV-diode array detector.

Keywords: Solid-phase microextraction; Organochlorine pesticides; High-performance liquid chromatography; Water analysis

Gas chromatography–electron capture detection determination of Dacthal and its di-acid metabolite in soil after ultrasound-assisted extraction and in situ focused microwave-assisted derivatization by A. Caballo-López; M. D. Luque de Castro (pp. 341-345).

A quantitative method for the determination of Dacthal and its di-acid metabolite in soil has been developed by coupling ultrasound-assisted extraction and microwave-assisted derivatization of the analytes prior to gas chromatography–electron capture detection for individual separation and measurement. The main factors affecting both extraction efficiency and derivatization were optimized by experimental design methodology. The proposed approach allows extraction of these pollutants from spiked sediment and soil with efficiencies similar to those provided by the reference method but with a drastic reduction of both the extraction and derivatization times. The repeatability of the analyses, expressed as RSD, of Dacthal and its di-acid metabolite was 4.6% and 5.4%, respectively; meanwhile, the RSD for within-laboratory reproducibility was 8.7% and 9.2%, respectively.

Keywords: Dacthal; Ultrasound; Microwave; Soil

Speciation of phytate ion in aqueous solution. Cadmium(II) interactions in aqueous NaCl at different ionic strengths by Concetta De Stefano; Demetrio Milea; Nunziatina Porcino; Silvio Sammartano (pp. 346-356).

Interactions between myo-inositol 1,2,3,4,5,6-hexakis(dihydrogen phosphate) (phytic acid) and cadmium(II) were studied by using potentiometry (at 25 °C with the ISE-H⁺ glass electrode) in different metal to ligand (Phy) ratios (1:1≤Cd²⁺:Phy≤4:1) in NaCl_aq at different ionic strengths (0.1≤I/mol L⁻¹≤1). Nine Cd_iH_jPhy^{(12−2i−j)−} species are formed with i=1 and 2 and 4≤j≤7; and trinuclear Cd₃H₄Phy²⁻. Dependence of complex formation constants on ionic strength was modeled by using Specific ion Interaction Theory (SIT) equations. Phytate and cadmium speciation are also dependent on the metal to ligand ratio. Stability of Cd_iH_jPhy^{(12−2i−j)−} species was modeled as a function of both the ligand protonation step (j) and the number of metal cations bound to phytate (i), and relationships found were used for the prediction of species other than those experimentally determined (mainly di- and tri-protonated complexes), allowing the possibility of modeling Phy and Cd(II) behavior in natural waters and biological fluids. A critical evaluation of phytate sequestering ability toward cadmium(II) has been made under several experimental conditions, and the determination of an empirical parameter has been proposed for an objective “quantification” of this ability. A thorough analysis of literature data on phytate–cadmium(II) complexes has been performed.

Keywords: Speciation analysis; Dependence on ionic strength; Predictive relationships; Cadmium–phytate complexes

Extraction and determination of hexavalent chromium in soil samples by Malgorzata Grabarczyk; Mieczyslaw Korolczuk; Katarzyna Tyszczuk (pp. 357-362).

A procedure for the extraction of Cr(VI) from solid soil-like samples was presented in which the complexing properties of diethylenetriaminepentaacetic acid (DTPA) were exploited to extract insoluble compounds of Cr(VI). A concentration of DTPA in an ammonium sulphate/ammonium hydroxide buffer equal to 0.02 mol l⁻¹ was chosen. The conditions of extraction of insoluble Cr(VI) from solid samples were optimised using soil certified reference material spiked with known concentration of insoluble Cr(VI) added as PbCrO₄. The extracts were analysed by adsorptive stripping voltammetry. Validation of the proposed procedure of extraction was carried out by analysis of certified reference material (CRM) 545 and comparison of the results obtained using the proposed and other methods of extraction in the course of analysis of natural soil samples.

Keywords: Chromium (VI); Soil; Extraction; Complexation; Determination

Iron fractionation for corrosion products from natural gas pipelines by continuous-flow sequential extraction by Nattikarn Kaewkhomdee; Chatvalee Kalambaheti; Somrudee Predapitakkun; Atitaya Siripinyanond; Juwadee Shiowatana (pp. 363-369).

The forms and quantities of iron species in corrosion product samples from natural gas pipelines were examined, using a continuous-flow sequential extraction system. Sequential extraction consists of four steps that dissolve water soluble iron (FeSO₄), acid soluble iron (FeCO₃), reducible iron (Fe-(oxyhydr)oxides) and oxidisable iron (FeS₂) fractions, respectively. Selectivity of extracting reagents for particular iron species was evaluated by determination of co-extracted anions, using ion chromatography, and evolved CO₂, using indirect flame atomic absorption spectrometer (FAAS). Iron was found predominantly in the reducible fraction (61–99%), indicating that Fe-(oxyhydr)oxides are the major constituents of the corrosion products.

Keywords: Corrosion product; Iron fractionation; Sequential extraction

Elucidation of n-butyl benzyl phthalate biodegradation using high-performance liquid chromatography and gas chromatography–mass spectrometry by Xiang-Rong Xu; Hua-Bin Li; Ji-Dong Gu (pp. 370-375).

n-Butyl benzyl phthalate (BBP) is an endocrine-disrupting chemical. A bacterium species capable of using BBP as the sole source of carbon and energy was isolated from mangrove sediment. Effects of BBP concentration, pH, temperature, and salinity on BBP biodegradation were studied. The optimum pH, temperature, and salinity for the BBP biodegradation were 7.0, 37°C, and 15 g L⁻¹, respectively. BBP was completely degraded within 6 days under optimum conditions, and the biodegradation of BBP could be fitted to a first-order kinetic model. The major metabolites of BBP biodegradation were identified as mono-butyl phthalate, mono-benzyl phthalate, phthalic acid, and benzoic acid by using high-performance liquid chromatography and gas chromatography–mass spectrometry. A preliminary metabolic pathway was proposed for the biodegradation of BBP.

Keywords: n-Butyl benzyl phthalate; Biodegradation; High-performance liquid chromatography; Gas chromatography–mass spectrometry

Determination of butyltin and octyltin stabilizers in poly(vinyl chloride) products by headspace solid-phase microextraction and gas chromatography with flame-photometric detection by Qin-Ren Ou; Chen-Wen Whang (pp. 376-381).

Headspace solid-phase microextraction (HS-SPME) and gas chromatography with flame photometric detection (GC-FPD) have been investigated for determination of butyltin and octyltin stabilizers in poly(vinyl chloride) (PVC) products. The organotin stabilizers were first released from the plastic matrix by dissolving the PVC sample in tetrahydrofuran (THF). The stabilizers were then hydrolyzed to the chloride forms, by treatment with 6 mol L⁻¹ HCl, then derivatized with sodium tetraethylborate (NaBEt₄) in 0.2 mol L⁻¹ sodium acetate buffer (pH 4.5) at 50 °C. HS-SPME was performed with a fused-silica fiber coated with a 100-μm film of polydimethylsiloxane (PDMS). The collected organotin compounds were then desorbed in the GC injector at 280 °C and analyzed by GC-FPD. Linearity (r≥0.994) over a concentration of approximately two orders of magnitude was usually obtained. Limits of quantitation (LOQ) of the four organotin compounds studied, viz., monobutyltin (MBT), dibutyltin (DBT), monooctyltin (MOT), and dioctyltin (DOT), were in the range 0.3–1.0 ng Sn mL⁻¹. Recovery was >90% for butyltins and >80% for octyltins. The method was validated by analyzing two reference standard PVC sheets with known organotin content. The applicability of the method to analysis of organotin stabilizers in commercial PVC products was also demonstrated.

Keywords: Organotin stabilizers; Poly(vinyl chloride); Solid-phase microextraction; Gas chromatography-flame photometric detection

Advanced CPMAS-¹³C NMR techniques for molecular characterization of size-separated fractions from a soil humic acid by Pellegrino Conte; Riccardo Spaccini; Alessandro Piccolo (pp. 382-390).

A humic acid extracted from a volcanic soil was subjected to preparative high-performance size-exclusion chromatography (HPSEC) to reduce its molecular complexity and eleven different size fractions were obtained. Cross-polarization magic-angle spinning ¹³C NMR (CPMAS ¹³C NMR) analysis performed with variable contact-time (VCT) pulse sequences showed that the largest molecular-size fractions contained aromatic, alkyl, and carbohydrate-like components. The carbohydrate-like content and the alkyl chain length seemed to decrease with decreasing molecular size. Progressive reduction of aromatic carbon atoms was also observed with decreasing molecular size of the separated fractions. Mathematical treatment of the results from VCT experiments enabled cross polarization (T _CH) and proton spin–lattice relaxation ( $$ T_{{1 ho }} {left( H ight)} $$ ) times to be related to structural differences among the size fractions. The conformational distribution indicated that the eleven size fractions could be allocated to two main groups. The first group, with larger nominal molecular sizes, was characterized by molecular domains with slower local molecular motion. The second group of size fractions, with smaller nominal molecular sizes, was characterized by a larger number of molecular domains with faster local molecular motion. The T _CH and $$ T_{{1 ho }} {left( H ight)} $$ values suggested that either condensed or strongly associated aromatic systems were predominant in the size fractions with the largest apparent molecular dimensions.

Keywords: CPMAS ¹³C NMR; HPSEC; Humic substances; Size fractions; Supramolecular associations; Variable contact time (VCT)

Full automation of solid-phase microextraction/on-fiber derivatization for simultaneous determination of endocrine-disrupting chemicals and steroid hormones by gas chromatography–mass spectrometry by Lihua Yang; Chongyu Lan; Hongtao Liu; Jun Dong; Tiangang Luan (pp. 391-397).

A fully automated method using direct immersion solid-phase microextraction (DI-SPME) and headspace on-fiber silylation for simultaneous determinations of exogenous endocrine-disrupting chemicals (EDCs) and endogenous steroid hormones in environmental aqueous and biological samples by gas chromatography–mass spectrometry (GC-MS) was developed and compared to a previously reported manual method. Three EDCs and five endocrine steroid hormones were selected to evaluate this method. The extraction and derivatization time, ion strength, pH, incubation temperature, sample volume, and extraction solvent were optimized. Satisfactory results in pure water were obtained in terms of linearity of calibration curve (R ²=0.9932–1.0000), dynamic range (3 orders of magnitude), precision (4–9% RSD), as well as LOD (0.001–0.124 μg L⁻¹) and LOQ (0.004–0.413 μg L⁻¹), respectively. These results were similar to those obtained using a manual method, and moreover, the precision was improved. This new automated method has been applied to the determinations of target compounds in real samples used in our previous study on a manual SPME method. Exogenous octylphenol (OP), technical grade nonylphenol (t-NP), and diethylstilbestrol (DES) were at 0.13, 5.03, and 0.02 μg L⁻¹ in river water and 3.76, 13.25, and 0.10 μg L⁻¹ in fish serum, respectively. Natural steroid hormones estrone (E₁), 17β-estradiol (E₂), and testosterone (T) were at 0.19, 0.11, and 6.22 μg L⁻¹ in river water; and in female fish serum E₁, E₂, and pregnenolone (PREG) were at 1.37, 1.95, and 6.25 μg L⁻¹, respectively. These results were confirmed by the manual method. The developed fully automated SPME and on-fiber silylation procedures showed satisfactory applications in environmental analysis and the performances show improved precision and a reduced analysis time compared to the manual method.

Keywords: Automated silylation; Nonylphenol; Octylphenol; Diethylstilbestrol; Steroid hormones; Water and biological samples

2007 Bunsen–Kirchhoff Award for Analytical Spectroscopy (pp. 398-398).

Determination of volatile residual solvents in pharmaceutical products by headspace liquid-phase microextraction gas chromatography-flame ionization detector by Xia Wang; Ting Jiang; Jinpeng Yuan; Chuange Cheng; Jianhua Liu; Junbo Shi; Rusong Zhao (pp. 399-399).

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Analytical and Bioanalytical Chemistry (v.386, #2)

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Analytical and Bioanalytical Chemistry (v.386, #2)