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Analytical and Bioanalytical Chemistry (v.376, #5)

Curiosity and wonder by John Fetzer (pp. 555-556).

Application of synchrotron radiation in chemistry—status and future by Arndt Knöchel (pp. 557-557).

X-ray microscopy: methods and perspectives by Gerd Schneider (pp. 558-561).

X-ray absorption spectroscopy to analyze nuclear geometry and electronic structure of biological metal centers—potential and questions examined with special focus on the tetra-nuclear manganese complex of oxygenic photosynthesis by Holger Dau; Peter Liebisch; Michael Haumann (pp. 562-583).

X-ray absorption spectroscopy (XAS) has become a prominent tool for the element-specific analysis of transition metals at the catalytic center of metalloenzymes. In the present study the information content of X-ray spectra with respect to the nuclear geometry and, in particular, to the electronic structure of the protein-bound metal ions is explored using the manganese complex of photosystem II (PSIII) as a model system. The EXAFS range carries direct information on the number and distances of ligands as well as on the chemical type of the ligand donor function. For first-sphere ligands and second-sphere metals (in multinuclear complexes), the determination of precise distances is mostly straightforward, whereas the determination of coordination numbers clearly requires more effort. The EXAFS section starts with an exemplifying discussion of a PSII spectrum data set with focus on the coordination number problem. Subsequently, the method of linear dichroism EXAFS spectroscopy is introduced and it is shown how the EXAFS data leads to an atomic resolution model for the tetra-manganese complex of PSII. In the XANES section the following aspects are considered: (1) Alternative approaches are evaluated for determination of the metal-oxidation state by comparison with a series of model compounds. (2) The interpretation of XANES spectra in terms of molecular orbitals (MOs) is approached by comparative multiple-scattering calculations and MO calculations. (3) The underlying reasons for the oxidation-state dependence of the XANES spectra are explored. Furthermore, the potential of modern XANES theory is demonstrated by presenting first simulations of the dichroism in the XANES spectra of the PSII manganese complex.

Keywords: Manganese complex; Metalloenzymes; Photosystem; XAFS; XANES

Application of time-resolved in-situ X-ray absorption spectroscopy in solid-state chemistry by T. Ressler (pp. 584-593).

Time-resolved X-ray absorption spectroscopy (TR-XAS) possesses excellent capabilities to reveal quantitative phase composition and average valence together with the evolution of the local structure of a system under dynamic reaction conditions. The work discussed here focused on time-resolved in-situ XAS investigations aiming, first, at understanding structural evolution under dynamic conditions and, second, at revealing properties of the system studied not available from investigations under stationary conditions. Hence, not only was the local structure of a material studied under reaction conditions, but characteristic properties of the reaction, such as reaction intermediates or the kinetics of the reaction, were also elucidated. The solid–gas reactions presented here clearly demonstrate the potential of TR-XAS investigations to extend the suitability of XAS for in-situ studies in solid-state chemistry to investigations under dynamic conditions.

Keywords: In situ; EXAFS; Catalysis; Structure–activity; X-ray absorption; Time-resolved; Solid-state

Recent synchrotron radiation microdiffraction experiments on polymer and biopolymer fibers by C. Riekel; M. C. García Gutiérrez; A. Gourrier; S. Roth (pp. 594-601).

The status of synchrotron radiation (SR) microdiffraction techniques developed at the ID13 beamline of the European Synchrotron Radiation Facility (ESRF) is reviewed for polymer and biopolymer fiber applications. Beam sizes in the micrometer-range have been used to study the local structure of whole fibers such as viscose-rayon or poly(p-phenylene terephthalamide). The possibilities for in situ studies during stretching, extrusion, or indentation will be discussed.

Online SAXS investigations of polymeric hollow fibre membranes by P. Klaus Pranzas; Arndt Knöchel; Klemens Kneifel; Helmut Kamusewitz; Thomas Weigel; Rainer Gehrke; Sérgio S. Funari; Regine Willumeit (pp. 602-607).

Polymeric membranes are used in industrial and analytical separation techniques. In this study small-angle X-ray scattering (SAXS) with synchrotron radiation has been applied for in-situ characterisation during formation of polymeric membranes. The spinning of a polyetherimide (PEI) hollow fibre membrane was chosen for investigation of dynamic aggregation processes during membrane formation, because it allows the measurement of the dynamic equilibrium at different distances from the spinning nozzle. With this system it is possible to resolve structural changes in the nm-size range which occur during membrane formation on the time-scale of milliseconds. Integral structural parameters, like radius of gyration and pair-distance distribution, were determined. Depending on the chosen spinning parameters, e.g. the flow ratio between polymer solution and coagulant water, significant changes in the scattering curves have been observed. The data are correlated with the distance from the spinning nozzle in order to get information about the kinetics of membrane formation which has fundamental influence on structure and properties of the membrane.

Keywords: Polymeric hollow fibre membrane; Small-angle X-ray scattering (SAXS); Synchrotron radiation; Membrane formation; Spinning parameters

Nanostructure evolution studies of bulk polymer materials with synchrotron radiation: progress in method development by Norbert Stribeck (pp. 608-617).

The prospects of a modern analysis of nanostructure evolution during the processing of polymer materials by means of scattering from synchrotron radiation are demonstrated in examples. The beam sources have gained stability, shortages are located in beamline setups and in method development for the quantitative analysis of voluminous data sets.By using the proposed multidimensional chord distribution function (CDF) analysis method, nanostructure information from small-angle X-ray scattering (SAXS) data are extracted and visualised. The method can be automated if the beamline setup is able to deliver a full data set with simple constraints. In this case even a simultaneous data evaluation is possible (while one pattern is accumulated, the previous one is analysed). The advantages of the method are demonstrated in a study of the straining of a thermoplastic elastomer. The possibilities of an automated analysis are demonstrated in an investigation of the crystallisation behaviour of high-pressure injection-moulded polyethylene (HPIM-PE). The achievable results of nanostructure analysis of polymer materials are discussed. It is shown that the time-resolved SAXS of polymer materials studied during a transformation and analysed by the CDF method is not just a powerful tool to investigate the relationship between structure and properties of materials; the information that can be gained concerning the processes that control nanostructure evolution is equally important. In the future the enlightenment of such relationships may help to tailor polymer materials with respect to their properties and, beyond that, to improve assessments concerning their aging.

Keywords: Synchrotron radiation; Instrument setup; SAXS; Polymer materials; Evaluation method; Automation

Characterisation of structure and aggregation processes of aquatic humic substances using small-angle scattering and X-ray microscopy by P. Klaus Pranzas; Regine Willumeit; Rainer Gehrke; Jürgen Thieme; Arndt Knöchel (pp. 618-625).

Aquatic humic substances (HS), an important part of the dissolved organic carbon in freshwater systems, are polyfunctional natural compounds with polydisperse structure showing strong aggregation/coagulation behaviour at high HS concentrations and in the presence of metal ions. In this study, small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS) and X-ray microscopy (XRM) were applied to characterise the structure and aggregation processes of HS in solution. In SAXS and XRM the high brilliant synchrotron radiation was used as X-ray source. Applying small-angle scattering, information about the size distribution and shape of aquatic HS was obtained. Spherical HS units were found which were stable in a wide concentration range in a kind of "monomeric" state almost independent of pH and ionic strength. At higher concentrations they formed chain-like agglomerates or disordered HS structures. In studies on the coagulation behaviour of HS after addition of copper ions, a linear relationship between Cu²⁺ concentration and the formation of large disordered HS-Cu²⁺ agglomerates was obtained. By using X-ray microscopy, single "huge" particles were found in older solutions and in solutions with high HS concentrations. Over a threshold Cu²⁺ concentration of approx. 300 mg/L, the formation of an extensive HS-Cu²⁺ network structure was observed within a few minutes. The presented structures show the ability of the methods used to characterise processes between diluted phase and suspended matter, which play an important role particularly in the region of phase interfaces.

Keywords: Aquatic humic substances; Humic and fulvic acids; Small-angle scattering; X-Ray microscopy; Structure; Aggregation processes

Instrumentation for FT-IR reflection spectroscopy with synchrotron radiation by M. Gensch; K. Hinrichs; A. Röseler; E. H. Korte; U. Schade (pp. 626-630).

A versatile experimental set-up for infrared reflectance measurements with synchrotron radiation and its adaptation to a beamline is presented. Particular consideration is given to the collimation and the polarization of incident radiation. The performance is characterized with experimental results. Due to the high brilliance of the synchrotron radiation source, the irradiation of samples smaller than 1 mm² was found to be improved by more than one order of magnitude when compared to a globar.

Keywords: Fourier transform infrared spectroscopy; FT-IR; Infrared synchrotron radiation; Reflection

Complexation of uranium(VI) with protocatechuic acid—application of iterative transformation factor analysis to EXAFS spectroscopy by A. Roßberg; T. Reich; G. Bernhard (pp. 631-638).

The speciation of 1 mM uranium(VI) in carbonate-free aqueous solutions of 50 mM protocatechuic acid (PCA, 3,4-dihydroxybenzoic acid) was studied in the pH range of 4.0 to 6.8 using EXAFS spectroscopy. The uranium L_III-edge EXAFS spectra were analyzed using a newly developed computer algorithm for iterative transformation factor analysis (FA). Two structural different uranium(VI) complexes were observed. The speciation in the pH range of 4.0 to 4.8 is dominated by a 1:2 or 1:3 uranium(VI)/PCA complex with bidentate coordination of the carboxyl group to the uranium(VI) moiety. Already at pH 4.6 significant amounts of a second species are formed. This uranium(VI) species contains two PCA ligands that are bound to the uranium via their neighboring phenolic hydroxyl groups under formation of five-member rings.

Keywords: Uranium; Protocatechuic acid; Complexation; EXAFS spectroscopy; Factor analysis; Speciation

Analysis of the cleaved topaz (001) surface by B. Struth; W. Hofmeister; D.-M. Smilgies; O. Konovalov (pp. 639-641).

We report on the first study of the cleaved (001) topaz surface and the characterization of the chemical composition and atomic arrangement of the surface. We conclude that there is strong evidence for a hydroxyl group termination appropriate for further chemical reactions. The surface itself is easily accessible, atomically flat and suitable for potential technological applications.

Keywords: Topaz; Surface; Synchrotron radiation

Optical sensor for carbon dioxide combining colorimetric change of a pH indicator and a reference luminescent dye by Naoki Nakamura; Yutaka Amao (pp. 642-646).

A new optical CO₂ sensor based on the luminescence intensity change of the europium(III) complex tris(thenoyltrifluoroacetonato) europium(III) dihydrate ([Eu(tta)₃]) caused by the absorption change of various pH indicators—thymol blue, phenol red, or cresol red—with CO₂ was developed and its CO₂ sensing properties were investigated. For all the CO₂ sensors using pH indicators the observed luminescence intensity from [Eu(tta)₃] at 613 nm increased with increasing CO₂ concentration. The linear calibration method based on the plot of (I₁₀₀−I₀)/(I−I₀) versus the inverse of CO₂ concentration was suggested, where I₀ and I₁₀₀ were luminescence intensities at 613 nm of the CO₂ sensor film in 100% nitrogen and 100% gaseous CO₂. In all cases the plots showed good linearity and the correlation factors of the plots, r², were 0.991 for thymol blue, 0.990 for phenol red, and 0.998 for cresol red. The slopes of the plots (A/B) for thymol blue, phenol red, and cresol red were 2.2, 5.2, and 9.0%, respectively. The response times of the CO₂ sensor film were 4.0 s for thymol blue, 4.4 s for phenol red, and 8.8 s for cresol red for switching from nitrogen to CO₂, and the recovery times of films were 36 s for thymol blue, 39.2 s for phenol red, and 56.6 s for cresol red for switching from CO₂ to nitrogen. The signal changes were fully reversible and hysteresis was not observed during the measurements. The highly sensitive CO₂ sensor was developed using thymol blue as an indicator for the CO₂-sensing probe.

Keywords: pH indicator; CO₂ sensor; Optical sensor; Colorimetric change

Measurement of the perfection of nanoscale multilayers by J. Thomas; J. Schumann; C. Kleint (pp. 647-652).

In modern materials science the characterisation of nanostructures is becoming increasingly important. For measurement of the quality of nanoscale multilayer arrangement with high spatial resolution a method is described that is based on the broadening of the spots in the Fourier transformation of transmission electron microscopic images of multilayer cross-sections. Using this method on Si/Ge superlattices with periodic lengths between 4 and 12 nm it could be quantitatively shown that the layer perfection decreases with increasing periodic length. The transition from elastic to plastic deformation between the Si and Ge layers at larger periodic lengths can be the reason for this behaviour.

Keywords: Quality of nanoscale multilayers; TEM; HRTEM; Si/Ge superlattices

Determination of low levels of free fibres of chrysotile in contaminated soils by X-ray diffraction and FTIR spectroscopy by E. Foresti; M. Gazzano; A. F. Gualtieri; I. G. Lesci; B. Lunelli; G. Pecchini; E. Renna; N. Roveri (pp. 653-658).

A new analytical method for the determination of low levels (0.01–1 wt%) of free fibres of chrysotile in contaminated clayey, sandy and sandy-organic soils is described. The detection limit of 0.01 wt% is reached with an enrichment of free fibres of chrysotile in the sample using a standard laboratory elutriator for sedimentation analysis. The chrysotile quantitative determination is performed both by X-ray powder diffraction, using the internal standard and reference intensity ratio methods, and by Fourier-transform infrared absorption spectroscopy. The procedure can be successfully applied to different soils after removal, by a thermal treatment, of the matrix components which can interfere. This straightforward method fulfils the request of public institutions and private companies for an appropriate quantitative determination of chrysotile-free fibres in contaminated soils.

Keywords: Asbestos; Chrysotile; X-ray diffraction; FTIR; Pollution; Environment

A thorough study of the surface wax of apple fruits by Giancarlo Verardo; Emanuela Pagani; Paola Geatti; Paolo Martinuzzi (pp. 659-667).

The composition of the surface waxes of three apple ( Malus domestica L.) cultivars ("Florina", "Golden B" and "Ozark Gold") has been studied by means of spectroscopic and GC–MS analysis of the class-fractionated mixture of components. Odd n -alkanes, mainly C₂₇ and C₂₉ molecules, are prevalent in the saturated fraction. Small concentrations of alkenes were also found; the C_28:1 component is strongly (72%) in excess over the other 1-alkenes. Straight-chain esters (mainly of palmitic acid) of saturated primary alcohols (C₁₈–C₃₀) were also detected; whereas the acyl moiety is made up essentially of an even number of carbons, the alcohol counterpart does not exhibit this characteristic. Aldehydes are present (C₂₀–C₃₀) with the homologue patterns C₂₆–C₃₀ most strongly represented. Straight-chain free secondary alcohols characterize the waxes of "Florina" and "Ozark Gold"; the hydroxy function is located far from the extremity of the carbon framework. Outstanding is the presence of three alcohols with 29 carbon centres. These alcohols are accompanied by free straight-chain primary alcohols, mainly with even-numbered carbon chains in the range C₂₆–C₃₀. Free fatty acids are present; all of have a framework of even-numbered carbon chains mainly in the range C₁₆–C₂₀. C_18:1 (oleic acid) is well represented.

Keywords: Apple; Cuticle wax; Chemical composition; Florina; Golden B; Ozark golden; Malus domestica

Study of VOC distribution in citrus fruits by chromatographic analysis by Magdalena Ligor; Bogusław Buszewski (pp. 668-672).

The contamination of various parts of citrus fruits by toluene (a representative of volatile organic compounds—VOCs) was analyzed. The model of contamination distribution, based on investigations of the sorption and accumulation of toluene in particular parts of citrus fruits was considered. Solvent extraction of components from fruit parts (waxy layer, cuticle, and pulp) was applied. The extracts were analyzed by gas chromatography. The sorption time profiles for such citrus fruits as kumquats and mandarins were determined by plotting the extracted mass, or the relationship C/C⁰, versus the sorption time of toluene. After the sorption process the highest concentration of toluene was observed in the flavedo, where the oil glands of kumquats and mandarins are located. The data obtained prove that the high dissolution of aromatic hydrocarbons results from the presence of essential oils in the oil glands. The diffusion coefficients of toluene for the cuticle and pulp of kumquats were also calculated. The results of model investigations were compared with the actual concentration of toluene in kumquats, citrons, mandarins and oranges from outdoor stands and orchards.

Keywords: Volatile organic compounds; Citrus fruit analysis; Solvent extraction; GC

Carbohydrate and alditol analysis by high-performance anion-exchange chromatography coupled with electrochemical detection at a cobalt-modified electrode by Innocenzo G. Casella; Michela Contursi (pp. 673-679).

A cobalt oxyhydroxide film dispersed on a carbon electrode surface was characterized and proposed as an amperometric sensor for determination of alditols and carbohydrates in flowing streams. Complex mixtures of carbohydrates were separated by anion-exchange chromatography using a moderately alkaline solution as mobile phase. The cobalt modified electrode (GC–Co) was employed under a constant applied potential of 0.5 V (vs Ag/AgCl). Under these experimental conditions the detection limits (S/N=3) for all analyzed electroactive molecules ranged between 0.3 μmol L⁻¹ and 1.5 μmol L⁻¹ and the dynamic linear ranges spanned generally three orders of magnitude above the relevant detection limits. Analytical determinations of carbohydrates and alditols in red and white wines, are reported.

Keywords: Carbohydrates; Alditols; Amperometric; Chromatography; Wine

Prediction of n -octanol/water partition coefficients for polychlorinated dibenzo- p -dioxins using a general regression neural network by G. Zheng; W. H. Huang; X. H. Lu (pp. 680-685).

A general regression neural network was used for the first time to study quantitative structure and property relationships of organic pollutants to correlate and predict n -octanol/water partition coefficients of polychlorinated dibenzo- p -dioxins from their topological molecular descriptors. In total, 42 polychlorinated dibenzo- p -dioxins and dibenzo- p -dioxins were available for this study—42 polychlorinated dibenzo- p -dioxins and dibenzo- p -dioxins in the training data set and 41 polychlorinated dibenzo- p -dioxins in the test data set. Partial least squares regression, back propagation network and general regression neural network models were trained using the training data set, and the accuracy of the models obtained were examined by the use of leave-one-out cross-validation. For prediction of the n -octanol/water partition coefficient, the best method is the general regression neural network. With the test data set, the correlation coefficient, root mean square error and mean absolute relative error for the general regression neural network model are 0.9276, 0.22 and 2.79%, respectively. For describing the structure of polychlorinated dibenzo- p -dioxins, the topological molecular descriptors outperform the mobile order and disorder thermodynamic method.

Keywords: GRNN; QSPR; logKow; PCDDs

A toxicity view of the pesticide picloram when immobilized onto a silica gel surface by Alexandre G. S. Prado; Claudio Airoldi (pp. 686-690).

The pesticide picloram (4-amino-3,5,6-trichloropicolinic acid) was anchored onto silica gel to yield a new surface. Isothermal microcalorimetry was applied to study the toxic effects caused to microbial activity of a typical Brazilian agricultural soil by application of free and immobilized picloram. The activity of the microorganisms in 1.50 g of soil sample was stimulated by addition of 6.0 mg of glucose plus 6.0 mg of ammonium sulfate under 34.8% controlled humidity at 298.15±0.02 K. The activity was recorded through power–time curves for increasing amounts of the active principle, varying from zero to 10.00 μg g⁻¹. The increasing amounts of picloram, either free or immobilized, caused a decrease of the original thermal effect. The calorimetric data showed that the anchored pesticide presented a much lower toxic effect than the free picloram on the microbial activity.

Keywords: Picloram; Silica; Calorimetry

Determination of hydroxyl radical by capillary electrophoresis and studies on hydroxyl radical scavenging activities of Chinese herbs by Yuhua Cao; Qingcui Chu; Jiannong Ye (pp. 691-695).

High-performance capillary electrophoresis (CE) with electrochemical detection (ED) was employed to determine hydroxyl radicals in the Fenton reaction. Hydroxyl radicals can react with salicylic acid to produce 2,3-dihydroxy benzoic acid and 2,5-dihydroxy benzoic acid, which can be analyzed by CE-ED. Based on this principle, hydroxyl radicals were determined indirectly. In a 20 mmol/L phosphate running buffer (pH 7.4), 2,3-dihydroxy benzoic acid and 2,5-dihydroxy benzoic acid would elute simultaneously from the capillary within 6 min. As the working electrode, a 300 μm diameter carbon-disk electrode exhibits good responses at +0.60 V (vs. SCE) for the two analytes. Peak currents of the two analytes are additive. Excellent linearity was obtained in the concentration range from 1.0×10^-3 mol/L to 5.0×10^-6 mol/L for 2,3-dihydroxy benzoic acid. The detection limit (S/N=3) was 2.0×10^-6 mol/L. This method was successfully applied for studying hydroxyl radical scavenging activities of Chinese herbs. It is testified that Apocynum Venetum L., Jinkgo bibola L., Morus alba L. and Rhododendron dauricum L. have strong hydroxyl radical scavenging activities.

Keywords: Capillary electrophoresis; Electrochemical detection; Hydroxyl radical; Chinese herbs

Potential parameters for the detection of hGH doping by A. Kniess; E. Ziegler; J. Kratzsch; D. Thieme; R. K. Müller (pp. 696-700).

The aim of our hGH application study with non-competitive athletes was the investigation of selected serum parameters from different processes affected by hGH. Fifteen athletes (age 21–33, mean 24) were treated with 0.06 IU hGH/kg BW per day or placebo (10 hGH, 5 placebo) respectively for 14 days. Blood samples were taken prior to, during and until 10 weeks after treatment.The concentrations of the following markers were determined in relevant serum samples: IGF-I, IGFBP-3, ALS, PIIINP, PINP, osteocalcin, and leptin. The IGF-I concentration increased rapidly within the hGH treatment group and showed significantly higher levels compared to baseline even 3 days after application. The response of the IGFBP-3 to the hGH applications was lower in comparison to IGF-I. The hGH group showed an increasing IGFBP-3 compared to baseline from day 4 till day 15. The response of PIIINP to hGH is clearly delayed compared to the IGF-I axis, but the PIIINP concentration remains on an increased level for a longer period (from day 4 until day 21). The time course and the extent of response varied strongly interindividually. PINP and osteocalcin showed only a small response to hGH applications. These parameters are characterised by a strong scattering of base values compared with the small response. In the hGH treatment group very different leptin concentrations were found at the beginning of the study, but after treatment decreasing leptin levels were observed in all cases.The determination of only one parameter will not be sufficient for detection of hGH abuse. A combination of markers by mathematical methods can be helpful to distinguish between placebo and hGH-treated athletes. By using the suggested discriminant function the data sets of hGH and placebo-treated athletes could be separated without false positive results.

Keywords: Doping; hGH; IGF-I; PIIINP; IGFBP-3; Bone and soft tissue markers; Sport

Determination of antifungal proteins in soil by liquid chromatography by Elek Bolygo; Dean Ricketts; Frank Moffatt; Michael Jessop; Sheila Attenborough (pp. 701-705).

A liquid chromatography method was developed for the determination of antifungal/antimicrobial proteins Rs-AFP1 and Dm-AMP1 in sandy loam soils. The extraction of these highly basic proteins was achieved by mechanical shaking with aqueous Tris buffer pH 9 containing guanidinium thiocyanate salt (4.1 M), EDTA and nonionic polyoxyethylene 20 cetyl ether, Brij-58 detergent. The extracts were cleaned up on Oasis HLB polymer solid-phase extraction cartridges and quantified by liquid chromatography fluorescence detection based on the fluorescence properties of the tryptophan content of these proteins. The detector response was linear for 0.3–10 μg mL⁻¹. Procedural recoveries were tested in the range 10–100 mg kg⁻¹. The limit of quantification was 10 mg kg⁻¹protein in the soil sample representing the lowest validated fortification level. The antifungal proteins were found to be stable in soil extract tested up to 9 days when stored at 4 °C.

Keywords: Antifungal; Antimicrobial; Proteins; AFPs; Rs-AFP1; Dm-AMP1; Defensins; Analysis from soils

Differential-pulse polarography (DPP) determination of betamethasone valerate in dosage form by J.-E. Belgaied (pp. 706-709).

The electrochemical reduction of betamethasone valerate (BV) in a pharmaceutical formulation containing neomycin has been carried out in Britton–Robinson buffer (BRB) (0.04 mol L⁻¹) by differential-pulse polarography (DPP). BV exhibits a well-defined irreversible reduction peak at −1.03 V/ref. The influence of pH on the reduction of BV was studied in Britton–Robinson buffer (pH range 1.7–10). A method for the analysis of BV in BRB (0.04 mol L⁻¹), which allows quantification over the range 3.9×10^–6–1.1×10^–4 mol L^–1, was proposed and successfully applied to the determination of BV in tablets with mean recovery and relative standard deviation of 100.81% and 0.45%, respectively.

Keywords: Corticosteroid; Betamethasone valerate

New colorimetric methods for the determination of trazodone HCl, famotidine, and diltiazem HCl in their pharmaceutical dosage forms by Magda M. Ayad; Abdalla Shalaby; Hisham E. Abdellatef; Mervat M. Hosny (pp. 710-714).

Two sensitive and simple spectrophotometric methods are developed for the determination of trazodone HCl, famotidine, and diltiazem HCl in pure and pharmaceutical preparations. The methods are based on the oxidation of the cited drugs with iron(III) in acidic medium. The liberated iron(II) reacts with 1,10-phenanthroline (method A) and the ferroin complex is colorimetrically measured at 510 nm against reagent blank. Method B is based on the reaction of the liberated Fe(II) with 2,2-bipyridyl to form a stable colored complex with λ _maxat 520 nm. Optimization of the experimental conditions was described. Beer's law was obeyed in the concentration range of 1–5, 2–12, and 12–32 μg mL^–1 for trazodone, famotidine, and diltiazem with method A, and 1–10 and 8–16 μg mL^–1 for trazodone and famotidine with method B. The apparent molar absorptivity for method A is 1.06×10⁵, 2.9×10⁴, 1.2×10⁴ and for method B is 9.4×10⁴and 1.6×10⁴, respectively. The suggested procedures could be used for the determination of trazodone, famotidine, and diltiazem, both in pure and dosage forms without interference from common excipients.

Keywords: Colorimetry; Trazodone HCl; Famotidine; Diltiazem HCl; Iron–phenanthroline; Iron–bipyridyl

Pressurized wet digestion in open vessels by B. Maichin; M. Zischka; G. Knapp (pp. 715-720).

The High Pressure Asher (HPA-S) was adapted with a Teflon liner for pressurized wet digestion in open vessels. The autoclave was partly filled with water containing 5% (vol/vol) hydrogen peroxide. The digestion vessels dipped partly into the water or were arranged on top of the water by means of a special rack made of titanium or PTFE-coated stainless steel. The HPA-S was closed and pressurized with nitrogen up to 100 bars. The maximum digestion temperature was 250 °C for PFA vessels and 270 °C for quartz vessels. Digestion vessels made of quartz or PFA-Teflon with volumes between 1.5 mL (auto sampler cups) and 50 mL were tested. The maximum sample amount for quartz vessels was 0.5–1.5 g and for PFA vessels 0.2–0.5 g, depending on the material. Higher sample intake may lead to fast reactions with losses of digestion solution. The samples were digested with 5 mL HNO₃ or with 2 mL HNO₃+6 mL H₂O+2 mL H₂O₂. The total digestion time was 90–120 min and 30 min for cooling down to room temperature. Auto sampler cups made of PFA were used as digestion vessels for GFAAS. Sample material (50 mg) was digested with 0.2 mL HNO₃+0.5 mL H₂O+0.2 mL H₂O₂. The analytical data of nine certified reference materials are also within the confidential intervals for volatile elements like mercury, selenium and arsenic. No cross contamination between the digestion vessels could be observed. Due to the high gas pressure, the diffusion rate of volatile species is low and losses of elements by volatilisation could be observed only with diluted nitric acid and vessels with large cross section. In addition, cocoa, walnuts, nicotinic acid, pumpkin seeds, lubrication oil, straw, polyethylene and coal were digested and the TOC values measured. The residual carbon content came to 0.2–10% depending on the sample matrix and amount.

Keywords: Wet digestion; Open vessel digestion; Pressurized digestion; Sample decomposition

Determination of titanium by slurry sampling graphite furnace atomic absorption spectrometry with the use of fluoride modifiers by Torunn Marie Sørlie; Grethe Wibetoe (pp. 721-727).

A method for the determination of titanium in graphite furnace atomic absorption spectrometry with slurry sampling was developed. Titanium forms thermally stable carbides in the graphite tube that leads to decreased sensitivity and severe memory effects. Various fluorinating agents, BaF₂, NH₄F, and CHF₃ (Freon-23) were therefore examined in order to reduce or eliminate these problems. Ti was determined, at various concentration levels, in certified reference materials (CRMs) using ultrasonic slurry sampling graphite furnace atomic absorption spectrometry (USS-GFAAS). The three CRMs, GBW 07601 (Human Hair Powder), GBW 07602 (Bush Branches and Leaves), and GBW 07411 (Chinese Soil), contained 2.7 μg g⁻¹, 95 μg g⁻¹, and 0.41% Ti, respectively. For comparison, determinations of Ti were made with modifiers (BaF₂ and NH₄F) and without modifier, using 5% CHF₃ (in argon) for cleaning the graphite furnace. Good accuracy was obtained using aqueous Ti standards for calibration. A homogeneity study showed that Ti was evenly distributed in all the samples at the mg–μg level. The relative standard deviations (RSDs) obtained for the three CRMs were 16%, 11%, and 8% (n=30). In spite of the wide range of Ti concentrations in the present samples, the same wavelength (365.4 nm) could be used for analysis by varying the slurry sample concentration. The precision was best for the material with the highest titanium content in spite of the fact that only 3 μg of sample was introduced into the furnace.

Keywords: Graphite furnace atomic absorption spectrometry; Titanium; Carbide formation; Memory effect; Fluoride modifier; Slurry sampling

Preconcentration using diethylenetriaminetetraacetic acid-functionalized polysiloxane (DETAP) for determination of molybdenum(VI) in seawater by ICP–OES by Jimmy C. Yu; S. M. Chan; ZuLiang Chen (pp. 728-734).

This paper reports a new method for preconcentration and separation of trace amounts of molybdenum in seawater samples prior to determination by inductively coupled plasma–atomic emission spectroscopy (ICP–OES). Diethylenetriaminetetraacetic acid-functionalized polysiloxane (DETAP) was synthesized by carboxymethylation of amino groups on triamine immobilized polymer, which was prepared by modification of 3-chloropropylpolysiloxane with diethylenetriamine. The resulting polysiloxane is highly selective and efficient in chelating Mo(VI) at trace levels. It can be used as a column packing material. The polysiloxane column can be reused over ten times without losing its original properties, so it is suitable for preconcentration of molybdenum species in seawater samples before determination. The parameters governing the characteristics of polysiloxane for adsorption of Mo(VI) were investigated. These include the effect of pH, amount of polysiloxane, equilibrium time, adsorption isotherm, maximum adsorption capacity, interfering ions, flow rate, capacity for reuse, and desorption. The precision of the preconcentration method, calculated as the relative standard deviation of seawater samples, was 3%. The preconcentration factor was 100. The detection limit, defined as 3 times the standard deviation of five replicate measurements of the blank sample at pH 3, was 0.17 μg L⁻¹. Measurement results for standard reference materials were in good agreement with the certified values [(CRMs), NASS-2 Seawater (Open Ocean) and CASS-2 Seawater (Coastal)].

Keywords: Molybdenum; Diethylenetriaminetetraacetic acid; Polysiloxane; ICP–OES

Interactions between 33 solutes and four cyano-containing stationary phases: gas chromatographic activity coefficients and the solvation parameter model by José M. Santiuste; József M. Takács (pp. 735-744).

Infinite-dilution gas–liquid chromatographic activity coefficients at 393.15 K (with their thermal and athermal components) and derived excess partial molar Gibbs energies, enthalpies, and entropies have been determined for each of 33 solutes of different polarity on four stationary phases with cyano groups, using retention data taken from the literature. The strongest interactions predicted by the solvation model are the dipolarity/polarizability, the acidic solute–basic stationary phase interaction, and nonpolar cavity formation and dispersion. These interactions were compared with those evaluated from the solute activity coefficients; the effect of the solute connectivity index and dipole moment on nonpolar and polar interactions, respectively, is discussed. The dependence of the thermal activity coefficient on nonpolar interactions, and the influence of stationary phase polarity on the four solute–stationary phase interactions, were evaluated. The nonpolar interaction increases with increasing connectivity and with increasing athermal activity coefficient. The dipolarity/polarizability interaction increases with increasing solute dipole moment. Finally, polar interactions increase with increasing stationary phase polarity whereas the nonpolar interaction is independent of stationary phase polarity.

Keywords: Gas chromatographic activity coefficients; Molecular connectivity indices; Solvation parameter model; Solute dipole moment; Stationary phase polarity; Correlations

Sulfonated and sulfoacylated poly(styrene–divinylbenzene) copolymers as packing materials for cation chromatography by Andrey V. Pirogov; Marina V. Chernova; Dar'ya S. Nemtseva; Oleg A. Shpigun (pp. 745-752).

Three different types of cation exchangers were produced from four basic poly(styrene–divinylbenzene) substrates with different properties. Porous PS-DVB resin beads were functionalized by sulfonation and sulfoacylation under various conditions to produce sulfonated resins with exchange capacities of 0.03–1.80 mM g⁻¹. The matrix with 50% of cross-linking is most suitable for updating by the proposed technique. Sulfuric and chlorosulfonic acids were used as the reagents for sulfonation. The sulfonating conditions, capacities, and the technique of the synthesis are given. The effects of parameters of the sulfonation reaction and the composition of the reactionary mixture on ion-exchange capacity of the sorbents were investigated. Selectivity and efficiency of the separation of some inorganic cations and derivatives of amines and hydrazines on the resins obtained are compared by ion chromatography with conductometric detection. As a result, the sulfoacylated resin was proved more efficient for the separation of these analytes. The resolution of the analytes strongly depends on the degree of functionalization. The best performance about 19,000 plates m⁻¹ was obtained using the sulfopropionylated beads with an ion-exchange capacity of 0.3 mM g⁻¹. The prepared sulfoacylated cation exchanger was compared with the commercially available Dionex CS-12 packing material. It was found that the separation of alkaline ions and 1,1-dimethylhydrazine (UDMH) were much better that those for the commercial material.

Keywords: Cation exchangers; Ion chromatography; Stationary phases; Polystyrene-divinylbenzene resins

Determination of mercury in SRM crude oils and refined products by isotope dilution cold vapor ICP-MS using closed-system combustion by W. Robert Kelly; Stephen E. Long; Jacqueline L. Mann (pp. 753-758).

Mercury was determined by isotope dilution cold-vapor inductively coupled plasma mass spectrometry (ID-CV-ICP-MS) in four different liquid petroleum SRMs. Samples of approximately 0.3 g were spiked with stable ²⁰¹Hg and wet ashed in a closed system (Carius tube) using 6 g of high-purity nitric acid. Three different types of commercial oils were measured: two Texas crude oils, SRM 2721 (41.7±5.7 pg g⁻¹) and SRM 2722 (129±13 pg g⁻¹), a low-sulfur diesel fuel, SRM 2724b (34±26 pg g⁻¹), and a low-sulfur residual fuel oil, SRM 1619b (3.5±0.74 ng g⁻¹) (mean value and 95% CI). The Hg values for the crude oils and the diesel fuel are the lowest values ever reported for these matrices. The method detection limit, which is ultimately limited by method blank uncertainty, is approximately 10 pg g⁻¹ for a 0.3 g sample. Accurate Hg measurements in petroleum products are needed to assess the contribution to the global Hg cycle and may be needed in the near future to comply with reporting regulations for toxic elements.

Keywords: Mercury; SRM; Crude oil; Carius; ICP-Ms

Speciation of Co(II), Co(III), and Cu(II) in ethylenediamine solutions by capillary electrophoresis by Evaldas Naujalis; Jurgita Čepytė; Audrius Padarauskas (pp. 759-762).

A capillary electrophoretic (CE) method for the speciation of Co(II), Co(III), and Cu(II) in electroless copper-plating baths containing ethylenediamine (En) has been developed. The method is based on the selective pre-capillary derivatization of Co(II) with 1,10-phenanthroline (Phen) followed by CE separation of stable [CoPhen₃]²⁺ , [CoEn₃]³⁺, and [CuEn₂]²⁺ chelates. The proposed derivatization procedure protects Co(II) from oxidation by dissolved oxygen and enables rapid determination of all three metal species within a single run. The optimized separations were carried out in a fused silica capillary (57 cm×75-μm I.D.) filled with an ethylenediamine sulfate electrolyte (20 mmol L^–1 H₂SO₄, pH 7.0 with En, applied voltage +30 kV) using direct UV detection at 214 nm. The detection limits for a signal-to-noise ratio of 3 and 10 s, hydrodynamic injections were 5×10^–6 mol L^–1 for Cu(II), 1×10^–6 mol L^–1 for Co(III), and 4×10^–7 mol L^–1 for Co(II). Application of the method to the speciation of Co(II), Co(III), and Cu(II) in copper-plating bath samples is also demonstrated.

Keywords: Capillary electrophoresis; Cobalt(II); Cobalt(III); Copper(II) ethylenediamine; 1,10-Phenanthroline; Derivatization

Evaluation of glycoalkaloids in tubers of genetically modified virus Y-resistant potato plants (var. Désirée) by non-aqueous capillary electrophoresis coupled with electrospray ionization mass spectrometry (NACE–ESI–MS) by Giuliana Bianco; Philippe Schmitt-Kopplin; Aniello Crescenzi; Soccorsa Comes; Antonius Kettrup; Tommaso R. I. Cataldi (pp. 763-764).

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Analytical and Bioanalytical Chemistry (v.376, #5)