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Analytica Chimica Acta (v.583, #2)

Contents (pp. iii-iv).

Calendar of forthcoming meetings (pp. n3).

Filler Advert SD Platform (pp. ii).

Editorial Board (pp. co1).

Contents (pp. iii-iv).

Filler Advert SD Platform (pp. ii).

Editorial Board (pp. co1).

Calendar of forthcoming meetings (pp. n3).

Coupling chemiluminescence with capillary electrophoresis to analyze single human red blood cells by Qing Zhi; Chao Xie; Xiangyi Huang; Jicun Ren (pp. 217-222).

In this paper, we describe a new method for determination of hemoglobin of single red blood cells by coupling chemiluminescence with capillary electrophoresis (CL–CE). The chemiluminescent detection is based on the catalytic effects of hemoglobin on the luminol–hydrogen peroxide reaction. The conditions of chemiluminescent reaction and capillary electrophoresis were investigated. Hemoglobin in human blood samples was detected with the present method, the linear range from 1.7μgmL⁻¹ to 6.8μgmL⁻¹ was tested, and the correlation coefficient of 0.997 and low detection limit of 0.17μgmL⁻¹ (approximately 2.2pg, S/N=3) were obtained. Cell injection procedure was improved, and the method was successfully used to determine hemoglobin of single red blood cells and the statistical result of the average content of hemoglobin in 26 human red blood cells was 23.6pg. Compared to other current methods, CE with CL system is simple, sensitive and will become an attractive alternative method for single cell analysis.

Keywords: Single cell analysis; Red blood cell; Hemoglobin; Chemiluminescence; Capillary electrophoresis

Coupling chemiluminescence with capillary electrophoresis to analyze single human red blood cells by Qing Zhi; Chao Xie; Xiangyi Huang; Jicun Ren (pp. 217-222).

Keywords: Single cell analysis; Red blood cell; Hemoglobin; Chemiluminescence; Capillary electrophoresis

Electrophoretic, size-exclusion high-performance liquid chromatography and liquid chromatography–electrospray ionization ion trap mass spectrometric detection of hemoglobin-based oxygen carriers by Phaedra Dora Simitsek; Panagiota Giannikopoulou; Haralabos Katsoulas; Efstathios Sianos; George Tsoupras; Maria-Helen Spyridaki; Costas Georgakopoulos (pp. 223-230).

Hemoglobin-based oxygen carriers (HBOCs) are blood substitutes based on hemoglobin of either bovine or human origin and they can potentially be misused in elite sports to improve endurance performance. Recently, three methods have been proposed in doping control analysis to allow HBOCs screening and identification by application of electrophoresis, size-exclusion chromatography coupled with HPLC and LC coupled with tandem mass spectrometry (LC/MSMS). In view of the Athens 2004 Olympic Games, modifications were introduced in order to increase the specificity of these methods. The sample preparation protocols of the electrophoretic and SEC–HPLC methods were modified with the introduction of sequential ultra filtration steps to remove all heme containing material below 100kDa, thus leaving only HBOCs material for analysis. Furthermore, a modification of the LC/MSMS methodology was introduced to allow full scan MS–MS spectra of peptide segments arising from the tryptic digestion of bovine HBOCs. These relatively simple methodological modifications have major impact, as far as time and cost effectiveness is concerned in doping control procedures, because they provide a useful tool in order to identify which suspect samples from the initial visual screening are due to hemolysis and exclude them from further analysis.

Keywords: Hemoglobin-based oxygen carriers; Electrophoresis; Size-exclusion high-performance liquid chromatography; Liquid chromatography–electrospray ionization tandem mass spectrometric; Doping control analysis

Polymer mediated capillary electrophoresis with attenuated total reflectance infrared microspectroscopy detection by B.M. Patterson; N.D. Danielson; A.J. Sommer (pp. 231-238).

Polymer mediated capillary electrophoresis (CE) using poly(diallyldimethylammonium chloride) (PDDAC) in the electrolyte with end-column single reflection attenuated total internal reflectance (ATR) Fourier transform infrared (FT-IR) microspectroscopy is presented. The terminus of the capillary is placed ∼1μm from the internal reflectance element (IRE), at the focus of the ATR infrared microscope. Electrophoretic separations of benzenesulfonate, 1-naphthalenesulfonate and 1,5-naphthalenesulfonate in a NaCl and PDDAC electrolyte using either −11 or −15kV are demonstrated with the CE-ATR FT-IR spectra providing identification of these compounds. Running electrolyte salt concentrations in the 0.85–1.7M range are required due to the 50–80mg mL⁻¹ sample concentrations. Increasing the NaCl salt concentration improves peak resolution but also increases analysis time. A PDDAC concentration as low as 0.0075% can facilitate the separation of the aromatic sulfonates while maintaining reasonable electroosmotic flow. Etching of the germanium IRE by the applied current, which can affect the intensity of the infrared beam, is corrected by fabrication of a plastic mounting post for the IRE to prevent current conduction through the IR instrument.

Keywords: Capillary electrophoresis; Infrared; Attenuated total internal reflection; Poly(diallyldimethylammonium chloride); Aromatic sulfonates

Polymer mediated capillary electrophoresis with attenuated total reflectance infrared microspectroscopy detection by B.M. Patterson; N.D. Danielson; A.J. Sommer (pp. 231-238).

Keywords: Capillary electrophoresis; Infrared; Attenuated total internal reflection; Poly(diallyldimethylammonium chloride); Aromatic sulfonates

Simultaneous liquid chromatographic determination of metals and organic compounds in pharmaceutical and food-supplement formulations using evaporative light scattering detection by Zdenek Spacil; Jana Folbrova; Nikolaos Megoulas; Petr Solich; Michael Koupparis (pp. 239-245).

A novel method for the non-derivatization liquid chromatographic determination of metals (potassium, aluminium, calcium and magnesium) and organic compounds (ascorbate and aspartate) was developed and validated based on evaporative light scattering detection (ELSD). Separation of calcium, magnesium and aluminium was achieved by the cation exchange column Dionex CS-14 and an aqueous TFA mobile phase according to the following time program: 0–6min TFA 0.96mLL⁻¹, 6–7min linear gradient from TFA 0.96–6.4mLL⁻¹. Separation of potassium, magnesium and aspartate was achieved by the lipophilic C₁₈ Waters Spherisorb column and isocratic aqueous 0.2mLL⁻¹ TFA mobile phase. Separation of sodium, magnesium, ascorbate and citrate was also achieved by the C₁₈ analytical column, according to the following elution program: 0–2.5min aqueous nonafluoropentanoic acid (NFPA) 0.5mLL⁻¹; 2.5–3.5min linear gradient from 0.5mLL⁻¹ NFPA to 1.0mLL⁻¹ TFA. In all cases, evaporation temperature was 70°C, pressure of the nebulizing gas (nitrogen) 3.5bar, gain 11 and the flow rate 1.0mLmin⁻¹. Resolution among calcium and magnesium was 1.8, while for all other separations was ≥3.2. Double logarithmic calibration curves were obtained within various ranges from 3–24 to 34–132μgmL⁻¹, and with good correlation ( r>0.996). Asymmetry factor ranged from 0.9 to 1.9 and limit of detection from 1.3 (magnesium) to 17μgmL⁻¹ (ascorbate).The developed method was applied for the assay of potassium, magnesium, calcium, aluminium, aspartate and ascorbate in pharmaceuticals and food-supplements. The accuracy of the method was evaluated using spiked samples (%recovery 95–105%, %R.S.D.<2) and the absence of constant or proportional errors was confirmed by dilution experiments.

Keywords: Evaporative light scattering detector; Pharmaceuticals; Sodium; Potassium; Aluminium; Calcium; Magnesium; Ascorbate; Aspartate; Citrate

Determination of priority organic micro-pollutants in water by gas chromatography coupled to triple quadrupole mass spectrometry by E. Pitarch; C. Medina; T. Portolés; F.J. López; F. Hernández (pp. 246-258).

A multiclass method has been developed for screening, quantification and confirmation of organic micro-pollutants in water by gas chromatography coupled to mass spectrometry with a triple quadrupole analyzer. The work has been focused on the determination of more than 50 compounds belonging to different chemical families: 19 organochlorine and organophosphorus insecticides, 6 herbicides, 7 polychlorinated biphenyls, 16 polycyclic aromatics hydrocarbons, 2 brominated diphenyl ethers, and 3 octyl/nonyl phenols and pentachlorobenzene. Most of these analytes are included in the list of priority substances in the framework on European Water Policy.Analyte extraction was performed by solid phase extraction using C₁₈ cartridges, and five isotopically labeled standards were added before extraction as surrogates. Analyses were performed by gas chromatography with tandem mass spectrometry (MS/MS) in electron impact mode. Accuracy and precision were evaluated by means of recovery experiments using water samples fortified at two concentration levels (25 and 250ngL⁻¹), with satisfactory results for most of analytes. The excellent selectivity and sensitivity reached in selected reaction monitoring mode allowed us satisfactory quantification and confirmation at levels as low as 25ngL⁻¹. Two MS/MS transitions were acquired for each analyte, using the Q/ q intensity ratio as a confirmatory parameter. The method developed was applied to the analysis of surface, ground and wastewater samples collected from the Valencia Region (Spain).Analytical methodology using negative chemical ionization mode was also validated for the organochlorine compounds selected, showing a superior sensitivity and lower detection limits.

Keywords: Water analysis; Organic pollutants; Gas chromatography tandem mass spectrometry; Triple quadrupole; Analyte confirmation

Quantification of deformed peaks in capillary gas chromatography (CGC): Application to simultaneous analysis of free fatty acids and less polar compounds in aqueous distillery effluent by E. Morin-Couallier; J. Bleton; M.L. Lameloise; A. Tchapla (pp. 259-265).

The purpose of this study was to find a simple and rapid method allowing the simultaneous quantification of some alcoholic fermentation inhibitors present in aqueous distillery effluent in order to evaluate its recycling properties. A capillary gas chromatography (CGC) method was tested for the quantification of both short chain fatty acids (acetic to hexanoic) and neutral compounds (butane 2,3-diol, 2-furaldehyde, phenyl-2-ethane1-ol). A polyvalent column coated with^®trifluoro-propyl-polysiloxane, allowing water injection, was tested and experiments were performed directly on untreated samples. During the development of the method, a deformation of acid peaks was observed; that could be explained by a secondary equilibrium, added to the chromatographic equilibrium. Although the acid peaks were deformed, calibration curves were produced and rigorously validated, proving that quantification is possible even when the best chromatographic conditions have not been achieved. Eventually, the method enabled the concentration of eight major fermentation inhibitors in distillery effluent to be measured.

Keywords: Capillary gas chromatography; Free fatty acids; Peak deformation; Effluent; Quantitative analysisAbbreviations; aa; Acetic Acid; pa; Propanoic Acid; ba; Butanoic Acid; va; Pentanoic Acid; ha; Hexanoic Acid; bdiol; Butane 2,3-diol; f; Furfural; phol; Phenyl-2-ethane1-ol

Characterisation of polycyclic aromatic hydrocarbons in atmospheric aerosols by gas chromatography–mass spectrometry by E. Borrás; L.A. Tortajada-Genaro (pp. 266-276).

An accurate and reliable method for determining polycyclic aromatic hydrocarbons (PAHs) in atmospheric aerosols is described. This optimised gas chromatography–mass spectrometry (GC–MS) method permits a wide range of concentrations to be analysed without the influence of interferences.Pre-treatment comparison of four kinds of aerosol collector filters determined that quartz and glass fibre filters were the most suitable. Solvents like cyclohexane, toluene, acetonitrile and dichloromethane were evaluated for their PAH-extraction capacity. Ultrasonic extraction using CH₂Cl₂ was selected because it is rapid and easy; moreover, this solvent increases the sample-throughput capacity.PAH compounds were quantitatively collected and ultrasonically extracted twice using 15mL of CH₂Cl₂ for 15min for each replicate. Rotavapor concentration, fractionation and dissolution were also optimised.A certified standard mixture (16 EPA PAHs), a deuterated compound and precision recovery assays were used for validating the proposed methodology. Adequate analytical parameters were obtained. Detection limits were (1.6–26.3)×10⁻⁵ng and quantification limits were (5.2–87.6)×10⁻⁵ng.Analysis of the environmental samples detected 4-10 EPA list PAH compounds. In addition, 2–11 tentative compounds were found, and their molecular structures were described for the first time.Our study of both Youden method and the standard addition method has shown that the proposed determination of PAHs in environmental samples is free of systematic errors.In conclusion, this unbiased methodology improves the identification and quantification of PAH compounds. High sensitivity as well as acceptable detection and quantification limits were obtained for the environmental applications.

Keywords: Polycyclic aromatic hydrocarbons; Atmospheric aerosols; Gas chromatography–mass spectrometry

Characterisation of polycyclic aromatic hydrocarbons in atmospheric aerosols by gas chromatography–mass spectrometry by E. Borrás; L.A. Tortajada-Genaro (pp. 266-276).

Keywords: Polycyclic aromatic hydrocarbons; Atmospheric aerosols; Gas chromatography–mass spectrometry

Application of ethyl chloroformate derivatization for gas chromatography–mass spectrometry based metabonomic profiling by Y. Qiu; M. Su; Y. Liu; M. Chen; J. Gu; J. Zhang; W. Jia (pp. 277-283).

A new combined gas chromatography and mass spectrometry (GC–MS) method has been developed suitable for the urine sample treatment in aqueous phase with ethyl chloroformate (ECF) derivatization agents. The method has been extensively optimized and validated over a broad range of different compounds and urine samples. Analysis of test metabolite derivatives, containing spiked standards, or rat urine exhibited acceptable linearity, satisfactory intra-batch precision (repeatability) and stability, relative standard deviations (R.S.D.) less than 10 and 15% within 48h, respectively. The quantification limits were 150–300pg on column for most metabolites. Recovery of several representative compounds, at different concentrations, ranged from 70 to 120%, with R.S.D. better than 10% for rat urine. We were able to generally eliminate potentially confounding variables such as medium complexity, different urea concentrations, and/or derivatization procedure variability. Metabonomic profiling of 1,2-dimethylhydrazine (DMH)-induced precancerous colon rat urine using GC–MS with ECF derivatization was performed to evaluate the proposed method. The analytical variation of the method was smaller than the biological variation in the rat urine samples, proving the suitability of the method to analyze differences in the metabonome of a living system with perturbed metabolic network. Thus, the proposed GC–MS analytical method is reliable to analyze a large variety of metabolites and can be used to investigate human pathology including disease onset, progression, and mortality.

Keywords: Ethyl chloroformate; Metabonomic profiling; Gas chromatography and mass spectrometry; Aqueous phase

Application of ethyl chloroformate derivatization for gas chromatography–mass spectrometry based metabonomic profiling by Y. Qiu; M. Su; Y. Liu; M. Chen; J. Gu; J. Zhang; W. Jia (pp. 277-283).

Keywords: Ethyl chloroformate; Metabonomic profiling; Gas chromatography and mass spectrometry; Aqueous phase

Identification of salicylic acid using surface modified polyurethane film using an imprinted layer of polyaniline by K. Sreenivasan (pp. 284-288).

The surface of polyurethane (PU) was modified by coating a thin layer of polyaniline (PAN) by oxidizing aniline using ammonium persulfate. Affinity sites for salicylic acid (SA) were created in the coated layer by non-covalent imprinting method. The imprinted layer adsorbed SA five times more compared to the nonimprinted surface reflecting the creation of affinity sites specific to SA on the surface. The equilibrium was attained relatively faster indicating that a material of this kind is suitable for sensing applications. The selectivity in recognizing the print molecule by the imprinted surface was assessed by comparing the extent of uptake of other structurally resembling molecules namely O-amino benzoic acid and acetyl salicylic acid. The selectivity factor was found to be 22 and 16.5. The adsorbed SA was detected using the technique of Fourier transform attenuated total internal reflection infrared spectroscopy (FT-ATR-IR). The results show that molecularly imprinted surface in combination with FT-IR is a useful approach for the sensing applications.

Keywords: Molecular imprinting; Polyaniline; Salicylic acid; Fourier transform infrared spectroscopy

Identification of salicylic acid using surface modified polyurethane film using an imprinted layer of polyaniline by K. Sreenivasan (pp. 284-288).

Keywords: Molecular imprinting; Polyaniline; Salicylic acid; Fourier transform infrared spectroscopy

Evaluation of surfactant assisted pressurized liquid extraction for the determination of glycyrrhizin and ephedrine in medicinal plants by Alan Teck Wee Eng; Ming Yuan Heng; Eng Shi Ong (pp. 289-295).

Surfactant assisted pressurized liquid extraction (PLE) with a laboratory made system was applied for the extraction of glycyrrhizin in Radix glycyrrhizae/liquorice and ephedrine in Ephedra sinica. The proposed system set-up for this current work was simpler as no heating and back pressure regulator was required. Extraction with surfactant assisted PLE was carried out dynamically at a flow of 1.5mLmin⁻¹, at room temperature, under an applied pressure of 10–20bar with an extraction time of 45–50min. The extraction efficiencies of the proposed method using surfactants such as sodium dodecyl sulfate (SDS) and Triton X-100 were compared with sonication using organic solvent for different batches of medicinal plants materials. For the determination of glycyrrhizin in R. glycyrrhizae, the extraction efficiencies of surfactant assisted PLE with SDS and Triton X-100 was observed to be comparable with sonication. The method precision was found to vary from 1.6 to 2.6% (R.S.D., n=6) on different days. For ephedrine in E. sinica, surfactant assisted PLE with SDS was found to give higher extraction efficiencies compared to Triton X-100. The overall method precision for surfactant assisted PLE with SDS for ephedrine in E. sinica was found to vary from 1.5 to 4.1% (R.S.D., n=6) on different days. The marker compounds present in the various medicinal plant extracts were determined by gradient elution HPLC. Our data showed the possibility of PLE at room temperature and the advantages of eliminating the use of organic solvents in the extraction process.

Keywords: Surfactant assisted pressurized liquid extraction; Medicinal plants; Ephedrine; Glycyrrhizin; High performance liquid chromatography; Extraction methods

Preconcentration of Zr, Hf, Nb, Ta and W in seawater using solid-phase extraction on TSK-8-hydroxyquinoline resin and determination by inductively coupled plasma-mass spectrometry by M. Lutfi Firdaus; Kazuhiro Norisuye; Taishi Sato; Shouhei Urushihara; Yusuke Nakagawa; Shigeo Umetani; Yoshiki Sohrin (pp. 296-302).

Here, we present the first simultaneous preconcentration and determination of ultratrace (pmolkg⁻¹ level) Zr, Hf, Nb, Ta and W in seawater, both in the form of dissolved and acid-dissolvable species. 8-Hydroxyquinoline (8HQ) bonded covalently to a vinyl polymer resin, TSK-8HQ, was used in a chelating adsorbent column to concentrate the metals. The greatest advantage of this resin is its endurance to 5M HF, since this is an effective eluent for all five metals. The analytes were successfully concentrated from 250mL seawater with a 50-fold concentration factor through the column extraction and evaporation. The detection limit was 0.009–0.15pmolkg⁻¹. The procedure blank determined using ultra pure water as a sample was 0.005–0.37pmolkg⁻¹. The five metals were quantitatively recovered from seawater with good precision (2–4%). The effect of sample pH, sample flow rate, eluent composition and sample pretreatment were carefully studied. This method was applied to seawater.

Keywords: Zr, Hf, Nb, Ta and W; Seawater; TSK-8HQ; Inductively coupled plasma-mass spectrometry

Determination of rare earth element in carbonate using laser-ablation inductively-coupled plasma mass spectrometry: An examination of the influence of the matrix on laser-ablation inductively-coupled plasma mass spectrometry analysis by Kazuya Tanaka; Yoshio Takahashi; Hiroshi Shimizu (pp. 303-309).

In this study, we examined the influence of the matrix on rare earth element (REE) analyses of carbonate with laser-ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) using carbonate and NIST glass standards. A UV 213nm Nd:YAG laser system was coupled to an ICP-MS. Laser-ablation was carried out in both He and Ar atmospheres to investigate the influence of ablation gas on the analytical results. A small amount of N₂ gas was added to the carrier gas to enhance the signal intensities. Synthetic CaCO₃ standards, doped with REEs, as well as NIST glasses (NIST SRM 610 and 612) were used as calibration standards. Carbonatite, which is composed of pure calcite, was analyzed as carbonate samples. The degree of the influence of the matrix on the results was evaluated by comparing the results, which were calibrated by the synthetic CaCO₃ and NIST glass standards. With laser-ablation in a He atmosphere, the differences between the results calibrated by the synthetic CaCO₃ and NIST glass standards were less than 10% across the REE series, except for those of La which were 25%. In contrast, for the measurements made in an Ar atmosphere, the results calibrated by the synthetic CaCO₃ and NIST glass standards differed by 25–40%. It was demonstrated that the LA-ICP-MS system can provide quantitative analysis of REE concentrations in carbonate samples using non matrix-matched standards of NIST glasses.

Keywords: Laser-ablation inductively-coupled plasma mass spectrometry; Carbonate; Rare earth element; Matrix effect

Authentication of Kalix (N.E. Sweden) vendace caviar using inductively coupled plasma-based analytical techniques: Evaluation of different approaches by I. Rodushkin; T. Bergman; G. Douglas; E. Engström; D. Sörlin; D.C. Baxter (pp. 310-318).

Different analytical approaches for origin differentiation between vendace and whitefish caviars from brackish- and freshwaters were tested using inductively coupled plasma double focusing sector field mass spectrometry (ICP-SFMS) and multi-collector inductively coupled plasma mass spectrometry (MC-ICP–MS). These approaches involve identifying differences in elemental concentrations or sample-specific isotopic composition (Sr and Os) variations. Concentrations of 72 elements were determined by ICP-SFMS following microwave-assisted digestion in vendace and whitefish caviar samples from Sweden (from both brackish and freshwater), Finland and USA, as well as in unprocessed vendace roe and salt used in caviar production. This data set allows identification of elements whose contents in caviar can be affected by salt addition as well as by contamination during production and packaging. Long-term method reproducibility was assessed for all analytes based on replicate caviar preparations/analyses and variations in element concentrations in caviar from different harvests were evaluated. The greatest utility for differentiation was demonstrated for elements with varying concentrations between brackish and freshwaters (e.g. As, Br, Sr). Elemental ratios, specifically Sr/Ca, Sr/Mg and Sr/Ba, are especially useful for authentication of vendace caviar processed from brackish water roe, due to the significant differences between caviar from different sources, limited between-harvest variations and relatively high concentrations in samples, allowing precise determination by modern analytical instrumentation. Variations in the⁸⁷Sr/⁸⁶Sr ratio for vendace caviar from different harvests (on the order of 0.05–0.1%) is at least 10-fold less than differences between caviar processed from brackish and freshwater roe. Hence, Sr isotope ratio measurements (either by ICP-SFMS or by MC-ICP–MS) have great potential for origin differentiation. On the contrary, it was impossible to differentiate between Swedish caviar processed from brackish water roe and Finnish freshwater caviar based solely on¹⁸⁷Os/¹⁸⁸Os ratios.

Keywords: Vendace caviar; Authentication; Inductively coupled plasma mass spectrometry; Elemental concentrations; Isotopic fingerprints

Trace element determination using static high-sensitivity inductively coupled plasma optical emission spectrometry (SHIP-OES) by Carsten Engelhard; Andy Scheffer; Sascha Nowak; Torsten Vielhaber; Wolfgang Buscher (pp. 319-325).

A low-flow air-cooled inductively coupled plasma (ICP) design for optical emission spectrometry (OES) with axial plasma viewing is described and an evaluation of its analytical capabilities in trace element determinations is presented. Main advantage is a total argon consumption of 0.6Lmin⁻¹ in contrast to 15Lmin⁻¹ using conventional ICP sources.The torch was evaluated in trace element determinations and studied in direct comparison with a conventional torch under the same conditions with the same OES system, ultrasonic nebulization (USN) and single-element optimization. A variety of parameters ( x– y-position of the torch, rf power, external air cooling, gas flow rates and USN operation parameters) was optimized to achieve limits of detection (LOD) which are competitive to those of a conventional plasma source.Ionic to atomic line intensity ratios for magnesium were studied at different radio frequency (rf) power conditions and different sample carrier gas flows to characterize the robustness of the excitation source. A linear dynamic range of three to five orders of magnitude was determined under compromise conditions in multi-element mode. The accuracy of the system was investigated by the determination of Co, Cr, Mn, Zn in two certified reference materials (CRM): CRM 075c (Copper with added impurities), and CRM 281 (Trace elements in rye grass). With standard addition values of 2.44±0.04 and 3.19±0.21μgg⁻¹ for Co and Mn in the CRM 075c and 2.32±0.09, 81.8±0.4, 32.2±3.9 for Cr, Mn and Zn, respectively, were determined in the samples and found to be in good agreement with the reported values; recovery rates in the 98–108% range were obtained. No influence on the analysis by the matrix load in the sample was observed.

Keywords: Inductively coupled plasma; Low-flow torch; Certified reference material; Optical emission spectrometry; Trace element determination; Static high-sensitivity ICP

Dynamic method as a simple approach for wide range pH measurements using optodes by A. Safavi; A.R. Banazadeh (pp. 326-331).

In this paper, a flow system equipped with an optode has been suggested for wide range pH measurements. Triacetyl cellulose was used as the optode membrane in which different pH indicators were immobilized. For extending the pH range, the dynamic response rather than the steady-state response of the optode was measured. Since diffusion is the main process governing the system response, different parameters having influence on diffusion of the analyte into the membrane were optimized. Under the optimum conditions, wide range pH determination (up to 11 pH units) is simply achieved regardless of the p K_a of the pH indicator immobilized in the membrane. To validate the application of the method different indicators with different structures and p K_a values were tested and the results were all confirming the precision and accuracy of the method. The suggested method also has combined advantages of flow systems together with inherent advantages of kinetic systems.

Keywords: Wide range pH determination; Dynamic; Optode

Dynamic method as a simple approach for wide range pH measurements using optodes by A. Safavi; A.R. Banazadeh (pp. 326-331).

Keywords: Wide range pH determination; Dynamic; Optode

Hydrogen peroxide and peracetic acid determination in waste water using a reversible reagentless biosensor by Vanesa Sanz; Susana de Marcos; Javier Galbán (pp. 332-339).

During the reversible reaction between peroxidase (HRP) and peroxides, several peroxidase intermediate species, showing different molecular absorption spectra, are formed which can be used for their determination. On this basis, a reversible reagentless optical biosensor based on HRP for hydrogen peroxide and peracetic acid determinations has been developed. The biosensor (which can be used for at least 3 months and/or more than 200 measurements) is prepared by HRP entrapment in a polyacrylamide gel matrix. A mathematical model (in which optical, kinetic and transport aspects are considered) relating the measured absorbance with the analyte concentration is also presented. Both peroxides show similar responses in the sensor film. Under the recommended working conditions, the biosensor shows linear response ranges from 6×10⁻⁷ to 1.0×10⁻⁴M using FIA mode, and from 2×10⁻⁷ to 1.5×10⁻⁵M using continuous mode for both peroxides; the precision, expressed as R.S.D., is about 4%. This biosensor has been applied for peroxide determination in waste water samples previously treated with peroxides.

Keywords: Reagentless biosensors; Hemeproteins; Hydrogen peroxide; Peracetic acid; Ultra violet-visible molecular absorption

Hydrogen peroxide and peracetic acid determination in waste water using a reversible reagentless biosensor by Vanesa Sanz; Susana de Marcos; Javier Galbán (pp. 332-339).

Keywords: Reagentless biosensors; Hemeproteins; Hydrogen peroxide; Peracetic acid; Ultra violet-visible molecular absorption

Schiff bases as cadmium(II) selective ionophores in polymeric membrane electrodes by V.K. Gupta; A.K. Singh; Barkha Gupta (pp. 340-348).

The construction and performance characteristics of polymeric membrane electrodes based on two neutral ionophores, N, N′-[bis(pyridin-2-yl)formylidene]butane-1,4-diamine (S₁) and N-(2-pyridinylmethylene)-1,2-benzenediamine (S₂) for quantification of cadmium ions, are described. The influences of membrane compositions on the potentiometric response of the electrodes have been found to substantially improve the performance characteristics. The best performance was obtained with the electrode having a membrane composition (w/w) of (S₁) (2.15%):PVC (32.2%): o-NPOE (64.5%):KTpClPB (1.07%). The proposed electrode exhibits Nernstian response in the concentration range of 7.9×10⁻⁸ to 1.0×10⁻¹M Cd²⁺ with limit of detection 5.0×10⁻⁸M, performs satisfactorily over wide pH range (2.0–8.0) with a fast response time (10s). The sensor has been found to work satisfactorily in partially non-aqueous media up to 30% (v/v) content of methanol, ethanol and acetonitrile and could be used for a period of 2 months. The analytical usefulness of the proposed electrode has been evaluated by its application in the determination of cadmium in real samples. The practical utility of the membrane electrode has also been observed in the presence of surfactants.

Keywords: Cadmium selective electrode; Poly(vinylchloride) membranes; Schiff base; Potentiometry and ion-selective electrodes

Schiff bases as cadmium(II) selective ionophores in polymeric membrane electrodes by V.K. Gupta; A.K. Singh; Barkha Gupta (pp. 340-348).

Keywords: Cadmium selective electrode; Poly(vinylchloride) membranes; Schiff base; Potentiometry and ion-selective electrodes

Homogeneous time-resolved fluorescence assays for the detection of activity and inhibition of phosphatase enzymes employing phosphorescently labeled peptide substrates by Desmond J. O'Shea; Tomás C. O’Riordan; Paul J. O'Sullivan; Dmitri B. Papkovsky (pp. 349-356).

A rapid, homogenous, antibody-free assay for phosphatase enzymes was developed using the phosphorescent platinum (II)-coproporphyrin label (PtCP) and time-resolved fluorescent detection. An internally quenched decameric peptide substrate containing a phospho-tyrosine residue, labeled with PtCP-maleimide and dabcyl-NHS at its termini was designed. Phosphatase catalysed dephosphorylation of the substrate resulted in a minor increase in PtCP signal, while subsequent cleavage by chymotrypsin at the dephosphorylated Tyr-Leu site provided a 3.5 fold enhancement of PtCP phosphorescence. This phosphorescence phosphatase enhancement assay was optimized to a 96 well plate format with detection on a commercial TR-F plate reader, and applied to measure the activity and inhibition of alkaline phosphatase, recombinant human CD45, and tyrosine phosphatases in Jurkat cell lysates within 40min. Parameters of these enzymatic reactions such as K_m's, limits of detection (L.O.D's) and IC₅₀ values for the non-specific inhibitor sodium orthovanadate were also determined.

Keywords: Metalloporphyrin labels; Phosphorogenic phosphopeptide substrates; Protein tyrosine phosphatases; Time-resolved fluorescence

Correction of inner-filter effect in fluorescence excitation-emission matrix spectrometry using Raman scatter by Tobias Larsson; Margareta Wedborg; David Turner (pp. 357-363).

Fluorescence excitation-emission matrix (EEM) spectroscopy is a useful tool for interpretation of fluorescence information from natural water samples. One of the major problems with this technique is the inner-filter effect (IFE), i.e. absorption of light at both the excitation and emission wavelengths. The common solutions are to either dilute the sample or apply some form of mathematical correction, most often based on the measured absorbance of the sample. Since dilution is not always possible, e.g . in on-line or in situ EEM recordings, and corrections based on absorbance are hampered primarily by the use of a separate absorbance instrument, neither of these solutions is optimal. In this work, we propose a mathematical correction procedure based on the intensity of Raman scatter from water. This procedure was found to reduce the error after correction by up to 50% in comparison with two absorbance correction procedures. Furthermore, it does not require the use of a separate absorbance measurement, and it is applicable to on-line and in situ EEM recordings, where the IFE would otherwise cause problems.

Keywords: Fluorescence; Excitation-emission matrix; Inner-filter effect; Absorbance correction

Correction of inner-filter effect in fluorescence excitation-emission matrix spectrometry using Raman scatter by Tobias Larsson; Margareta Wedborg; David Turner (pp. 357-363).

Keywords: Fluorescence; Excitation-emission matrix; Inner-filter effect; Absorbance correction

Room temperature phosphorescence of α-bromonaphthalene induced by cyclodextrin in the presence of hexahydropyridine or 1-ethylpiperidine and its application by Ya-Xian Zhu; Jing-He Peng; Yong Zhang (pp. 364-369).

Two novel heterocyclic third components, hexahydropyridine (HHP) and 1-ethylpiperidine (EP) were firstly found to enhance room temperature phosphorescence (RTP) of α-bromonaphthalene (α-BrN) induced by cyclodextrin. The effects of equilibrium time for formation of inclusion complex, temperature, pH values and the variation of concentrations of each component on RTP of α-BrN and the RTP lifetime of each ternary complex had been investigated and compared to discuss inclusion mechanism of ternary complexes. The RTP lifetimes of α-BrN/β-CD/HHP, α-BrN/β-CD/cyclohexane (CH) and α-BrN/β-CD/EP were 6.18, 7.71 and 9.36ms, respectively. Based on the strongest RTP of α-BrN induced by CD in the presence of EP, a method for determination of EP was established. Under the optimal conditions, the analytical curve of EP gave a liner dynamic range of 1.50×10⁻⁴ to 1.50×10⁻³molL⁻¹ with a detection limit of 4.8×10⁻⁵molL⁻¹. When the established CD-RTP method was applied to determine the concentration of EP synthetic samples in distilled water, the experimental results demonstrated that the recovery was 91.4% with a relative standard deviation less than 2.85% ( n=7).

Keywords: Room temperature phosphorescence; Cyclodextrin; α-Bromonaphthalene; 1-Ethylpiperidine; Hexahydropyridine

Immunoassay for iprodione: Key estimation for residue analysis and method validation with chromatographic technique by Eiki Watanabe; Shiro Miyake (pp. 370-376).

This work reports on the fundamental characteristics of a commercial enzyme-linked immunosorbent assay (ELISA) for iprodione and the application to residue analysis in agricultural samples. The ELISA had enough analytical sensitivity ( I₅₀ value 4.0ngg⁻¹; limit of detection 0.3ngg⁻¹) to determine a trace of iprodione residue and had a high selectivity. Only administering simple dilution of sample extracts very easily surmounted the most troublesome matrix interference in ELISA for pesticide residue analysis. Consequently, a rapid and simple detection method for iprodione was reached by the combination of the sample dilution and the devised extraction method in which it required no instruments for extraction. The average recovery values from spiked samples with the ELISA were between 106.4 and 115.8% with the average coefficients of variation between 3.0 and 4.0%. The results obtained with the ELISA correlated well with those by the reference chromatographic method for all tested agricultural samples ( r>0.993). These findings strongly indicate that the proposed ELISA was an adequate and reliable detection method for iprodione residues.

Keywords: Iprodione; Pesticide residue; Enzyme-linked immunosorbent assay (ELISA); Immunoassay; Chromatographic analysis; Validation

Immunoassay for iprodione: Key estimation for residue analysis and method validation with chromatographic technique by Eiki Watanabe; Shiro Miyake (pp. 370-376).

Keywords: Iprodione; Pesticide residue; Enzyme-linked immunosorbent assay (ELISA); Immunoassay; Chromatographic analysis; Validation

Immunochemical method for sulfasalazine determination in human plasma by Nuria Pastor-Navarro; Ester Gallego-Iglesias; Ángel Maquieira; Rosa Puchades (pp. 377-383).

Sulfasalazine is an antibiotic used in the treatment of inflammatory bowel diseases. For the assessment of sulfasalazine in several biological matrices, an Enzyme-Linked Immunosorbent Assay (ELISA) method based on polyclonal antibodies was developed and characterized.The immunoassay showed a high sensitivity (IC₅₀=0.51ngmL⁻¹) and specificity, a detection limit of 0.02ngmL⁻¹ and a dynamic range of 0.06–3.75ngmL⁻¹ (80–20% inhibition). The immunoassay performed well when it was applied to spiked plasma samples (from 0.5 to 2.0ngmL⁻¹) previously cleaned up by protein precipitation with methanol. Recoveries ranged from 83 to 119%, with a mean value of 99% (CV=13%).Since sulfasalazine remaining of a treatment reaches the systemic circulation in unchanged form, the immunoassay can be applied to the determination of this pharmaceutical in human plasma in order to facilitate the control of the patients through the application of personal doses.

Keywords: Sulfasalazine; Enzyme-Linked Immunosorbent Assay; Human plasma; Polyclonal antibodies

Immunochemical method for sulfasalazine determination in human plasma by Nuria Pastor-Navarro; Ester Gallego-Iglesias; Ángel Maquieira; Rosa Puchades (pp. 377-383).

Keywords: Sulfasalazine; Enzyme-Linked Immunosorbent Assay; Human plasma; Polyclonal antibodies

Determination of trace halogens in rock samples by radiochemical neutron activation analysis coupled with the k₀-standardization method by Hiromasa Ozaki; Mitsuru Ebihara (pp. 384-391).

Radiochemical neutron activation analysis coupled with the k₀-standardization method ( k₀-RNAA method) was applied to silicate rock samples for the simultaneous determination of trace halogens (Cl, Br and I). Analytical results obtained by the k₀-RNAA method for geological standard rocks and meteorite samples agreed with those determined by the conventional comparison method conducted in the same set of experiments, suggesting that the k₀-RNAA method is as reliable as the conventional method. Our data for these samples are in good agreement with their literature values except for rare cases. Detection limits calculated under the present experimental condition are sufficiently low for Cl and Br but not for I for typical geologic and meteoritic samples. The k₀-RNAA method coupled with longer neutron-irradiation is expected to yield satisfactorily low detection limits for halogens including I in these samples.

Keywords: Halogens; Radiochemical neutron activation analysis; k; ₀; -Standardization; Geological samples; Cosmochemical samples

Determination of trace halogens in rock samples by radiochemical neutron activation analysis coupled with the k₀-standardization method by Hiromasa Ozaki; Mitsuru Ebihara (pp. 384-391).

Keywords: Halogens; Radiochemical neutron activation analysis; k; ₀; -Standardization; Geological samples; Cosmochemical samples

Kinetic analysis of reactions of Si-based epoxy resins by near-infrared spectroscopy,¹³C NMR and soft–hard modelling by Mariano Garrido; Maria Soledad Larrechi; F. Xavier Rius; Luis Adolfo Mercado; Marina Galià (pp. 392-401).

Soft- and hard-modelling strategy was applied to near-infrared spectroscopy data obtained from monitoring the reaction between glycidyloxydimethylphenyl silane, a silicon-based epoxy monomer, and aniline. On the basis of the pure soft-modelling approach and previous chemical knowledge, a kinetic model for the reaction was proposed. Then, multivariate curve resolution-alternating least squares optimization was carried out under a hard constraint, that compels the concentration profiles to fulfil the proposed kinetic model at each iteration of the optimization process. In this way, the concentration profiles of each species and the corresponding kinetic rate constants of the reaction, unpublished until now, were obtained. The results obtained were contrasted with¹³C NMR. The joint interval test of slope and intercept for detecting bias was not significant ( α=5%).

Keywords: Epoxy resins; Silicon; Multivariate curve resolution; Alternating least squares; Soft and hard modelling; Kinetic model; Flame retardants; Nuclear magnetic resonance; near infrared

Presence of virgin olive oil phenolic metabolites in human low density lipoprotein fraction: Determination by high-performance liquid chromatography–electrospray ionization tandem mass spectrometry by Karina de la Torre-Carbot; Jorge L. Chávez-Servín; Olga Jaúregui; Ana I. Castellote; Rosa M. Lamuela-Raventós; Montserrat Fitó; María-Isabel Covas; Daniel Muñoz-Aguayo; M. Carmen López-Sabater (pp. 402-410).

The biological benefits of olive oil in preventing the oxidation of low density lipoprotein (LDL) would seem to be linked to its high monounsaturated fatty acid contents, but also to its respective phenolic compounds contents. One prerequisite to assess the in vivo physiological significance of phenolic compounds is to determine their presence in human LDL following the ingestion of virgin olive oil.In this work, olive oil phenolic metabolites were identified using high-performance liquid chromatography in tandem with electrospray mass spectrometry (HPLC–ESI-MS/MS) detection, after solid phase extraction (SPE). Quantitative methods were developed in carrying out linearity, precision, sensitivity and recovery tests. The results from two methods of LDL separation were compared and shorter LDL isolation procedure showed a better recovery for antioxidants compounds in LDL. The metabolites identified in LDL were: hydroxytyrosol monoglucuronide, hydroxytyrosol monosulfate, tyrosol glucuronide, tyrosol sulfate and homovanillic acid sulfate. The fact that olive oil phenolic metabolites are able to bind LDL strengthens claims that these compounds act as in vivo antioxidants.

Keywords: Abbreviations; HPLC–ESI-MS/MS; high-performance liquid chromatography in tandem with electrospray mass spectrometry; LDL; low density lipoprotein; SPE; solid phase extraction; DAD; diode array detector; IS; internal standard; DP; declustering potential; MRM; multiple reaction monitoring; CE; collision energy; CAD; collision-activated dissociation; LOD; limit of detection; LOQ; limit of quantification; Apo-B; Apolipoprotein-B; R.S.D.; relative standard deviation; u; atomic mass unitsOlive oil; Low density lipoprotein; Hydroxytyrosol; Tyrosol; Homovanillic acid; Phenolic metabolites; High-performance liquid chromatography; Mass spectrometry; Solid phase extraction

Usefulness of the direct coupling headspace–mass spectrometry for sensory quality characterization of virgin olive oil samples by Silvia López-Feria; Soledad Cárdenas; José Antonio García-Mesa; Miguel Valcárcel (pp. 411-417).

The applicability of the headspace coupled to mass spectrometry for evaluation of the sensory quality of virgin olive oil samples is presented. The volatiles of the oil are directly transferred from the sample vial to the detector without chromatographic separation. The mass spectrum obtained can be considered as a fingerprint of the oil sample and can be used for classification purposes. After a training step with samples previously qualified following the official method, a classification model was created using the supervised technique soft independent modeling of class analogy (SIMCA). Eight negative (rancid, winey-vinegary, muddy sediment, hay-wood, vegetable water, earthy, fusty and musty-humidity) and three principal positive attributes (fruity, bitter and pungent) have been included in this study. With them, a classification model consisting of two main classes (extra- and lampante-virgin olive oil) was constructed. In addition, the unsupervised technique cluster analysis permited the discrimination among oils with different negative attributes. The proposed procedure has been applied to the classification of commercial samples (as extra- or lampante-virgin olive oils) and the results were compared with those provided by the expert's panel with acceptable correlation.

Keywords: Headspace; Mass spectrometry; Olive oil sensory quality; Direct analysis; Chemometric techniques

Potentiometric and spectrophotometric p K_a determination of water-insoluble compounds: Validation study in a new cosolvent system by Gergely Völgyi; Rebeca Ruiz; Karl Box; John Comer; Elisabeth Bosch; Krisztina Takács-Novák (pp. 418-428).

In this paper the validation of p K_a determination in MDM–water mixtures is presented. The MDM–water mixture is a new multicomponent cosolvent mixture (consisting of equal volumes of methanol, dioxane and acetonitrile, as organic solvents) that dissolves a wide range of poorly water-soluble compounds. The cosolvent dissociation constants (p_s K_a) of 50 chemically diverse compounds (acids, bases and ampholytes) were measured in 15–56wt% MDM–water mixtures by potentiometric or spectrophotometric titration and the aqueous p K_a values obtained by extrapolation. Three different extrapolation procedures were compared in order to choose the best extrapolation in MDM–water mixture using a sub-set of 30 water-soluble compounds. The extrapolated results are in good agreement with p K_a values measured in aqueous medium. No significant difference was found among these extrapolation procedures thus the widely used Yasuda–Shedlovsky plot was proposed for MDM cosolvent also. Further we also present that the single point estimation based on measurement in 20%/v MDM-mixture using a general calibration equation may be suitable for rapid p K_a determination in the early phase of drug research.

Keywords: p; K; _a; Cosolvent procedure; Methanol/dioxane/acetonitrile–water (MDM); Validation

Development of a tubular fluoride potentiometric detector for flow analysis by João Rodrigo Santos; R.A.S. Lapa; José L.F.C. Lima (pp. 429-436).

In this work a construction procedure for tubular fluoride electrode to be used in flow systems is outlined. The electrode was constructed from a commercially available, LaF₃ single crystal. Principal advantages of the flow detector presented include simplicity of construction, robustness, durability, low cost and easy coupling into any point of a flow manifold.Evaluation of the intrinsic working characteristics of the potentiometric detector in a low dispersion manifold is presented with respect to analytical and dynamic parameters. The constructed detector has similar working characteristics to those of the conventional fluoride electrodes, namely the detection limit, lower limit of linear response and operational pH range.The analytical usefulness of the constructed device was assessed in a flow system developed for fluoride determination in toothpaste, tablet, collutory and water samples for which the reference procedures suggest the determination of fluoride ion with a conventional ion selective electrode.

Keywords: Tubular fluoride electrode; Flow injection analysis; Potentiometry

Development of a tubular fluoride potentiometric detector for flow analysis by João Rodrigo Santos; R.A.S. Lapa; José L.F.C. Lima (pp. 429-436).

Keywords: Tubular fluoride electrode; Flow injection analysis; Potentiometry

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Analytica Chimica Acta (v.583, #2)