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Analytical and Bioanalytical Chemistry (v.381, #2)

Sample preparation for speciation by Carmen Cámara (pp. 277-278).

Passive sampling and/or extraction techniques in environmental analysis: a review by Jacek Namieśnik; Bożena Zabiegała; Agata Kot-Wasik; Monika Partyka; Andrzej Wasik (pp. 279-301).

The current state-of-the-art of passive sampling and/or extraction methods for long-term monitoring of pollutants in different environmental compartments is discussed in this review. Passive dosimeters that have been successfully used to monitor organic and inorganic contaminants in air, water, sediments, and soil are presented. The application of new approaches to the determination of pollutants at the sampling stage is discussed. The main milestones in the development of passive techniques for sampling and/or extraction of analytes, and in biomonitors used in environmental analysis, are summarized in this review. Passive samplers and biomonitors are compared.

Keywords: Sampling/extraction techniques; Passive sampling; Environmental analysis; Solid-phase microextraction; Biomonitoring; Speciation

Metal fractionation of atmospheric aerosols via sequential chemical extraction: a review by Patricia Smichowski; Griselda Polla; Darío Gómez (pp. 302-316).

This review surveys schemes used to sequentially chemically fractionate metals and metalloids present in airborne particulate matter. It focuses mainly on sequential chemical fractionation schemes published over the last 15 years. These schemes have been classified into five main categories: (1) based on Tessier’s procedure, (2) based on Chester’s procedure, (3) based on Zatka’s procedure, (4) based on BCR procedure, and (5) other procedures. The operational characteristics as well as the state of the art in metal fractionation of airborne particulate matter, fly ashes and workroom aerosols, in terms of applications, optimizations and innovations, are also described. Many references to other works in this area are provided.

Keywords: Chemical fractionation; Fractionation schemes; Metals and metalloids; Airborne particulate matter; Fly ashes; Workroom aerosols

Pretreatment procedures for characterization of arsenic and selenium species in complex samples utilizing coupled techniques with mass spectrometric detection by Katarzyna Wrobel; Kazimierz Wrobel; Joseph A. Caruso (pp. 317-331).

Research interest in analyzing arsenic and selenium is dictated by their species-dependent behavior in the environment and in living organisms. Different analytical methodologies for known species in relatively simple chemical systems are well established, yet the analysis of complex samples is still a challenge. Owing to the complex matrix and low concentrations of target species that may be chemically labile, suitable pretreatment of the sample becomes a critical step in any speciation procedure. In this paper, the pretreatment procedures used for arsenic and selenium speciation are reviewed with the emphasis on the link between the analytical protocol applied and the biologically-significant information provided by the results obtained. In the first approach, the aim of pretreatment is to convert the original sample into a form that can be analyzed by a coupled (hyphenated) technique, preventing possible losses and/or species interconversion. Common techniques include different leaching and extraction modes, enzymatic hydrolysis, species volatilization, and so on, with or without species preconcentration. On the other hand, if the speciation analysis is performed for elucidation of elemental pathways and specific functions in a living system, more conscious pretreatment and/or fractionation is needed. The macroscopic separation of organs and tissues, isolation of certain types of cells, cell disruption and separation of sub-cellular fractions, as well as isolation of a specific biomolecules become important. Furthermore, to understand molecular mechanisms, the identification of intermediate—often highly instable—metabolites is necessary. Real life applications are reviewed in this work for aquatic samples, soils and sediments, plants, yeast, and urine.

Arsenic speciation in hair extracts by Andrea Raab; J. Feldmann (pp. 332-338).

Ingested arsenic is known to be not only excreted by urine, but to be stored in sulphydryl-rich tissue like hair, nail or skin. We developed an extraction method for arsenic species from these tissues and studied the stability of different arsenic species during the extraction process. Inorganic and pentavalent methylated arsenic was found to be stable under the extraction conditions, whereas trivalent methylated arsenicals and the thio-analogue of DMA^V (DMAS) showed reduced stability. The absorption ability of hair for these different species was studied as well. Inorganic arsenic is better absorbed by hair than monomethyl- or dimethyl-arsenicals, whereby the trivalent forms are taken up better than the pentavalent forms. Independent of which methylated arsenical was used for the incubation, the pentavalent form was always the dominant form after extraction. Hair and nail samples from humans suffering from chronic arsenic intoxication contained dominantly inorganic arsenic with small and strongly varying amounts of DMA^V and MA^V present. DMAS was only found in some nail sample extracts containing unusually high amounts of DMA^V and is believed to be formed during the extraction process.

Keywords: Arsenic speciation; Sample preparation; Hair analysis; HPLC-ICP-MS; Accumulation potential; Species transformation

Determination of inorganic arsenic in white fish using microwave-assisted alkaline alcoholic sample dissolution and HPLC-ICP-MS by Erik H. Larsen; Joakim Engman; Jens J. Sloth; Marianne Hansen; Lars Jorhem (pp. 339-346).

An analytical method for the determination of inorganic arsenic in fish samples using HPLC-ICP-MS has been developed. The fresh homogenised sample was subjected to microwave-assisted dissolution by sodium hydroxide in ethanol, which dissolved the sample and quantitatively oxidised arsenite (As(III)) to arsenate (As(V)). This allowed for the determination of inorganic arsenic as a single species, i.e. As(V), by anion-exchange HPLC-ICP-MS. The completeness of the oxidation was verified by recovery of As(V) which was added to the samples as As(III) prior to the dissolution procedure. The full recovery of As(V) at 104±7% (n=5) indicated good analytical accuracy. The uncertified inorganic arsenic content in the certified reference material TORT-2 was 0.186±0.014 ng g⁻¹ (n=6). The method was employed for the determination of total arsenic and inorganic arsenic in 60 fish samples including salmon from fresh and saline waters and in plaice. The majority of the results for inorganic arsenic were lower than the LOD of 3 ng g⁻¹, which corresponded to less than one per thousand of the total arsenic content in the fish samples. For mackerel, however, the recovery of As(III) was incomplete and the method was not suited for this fat-rich fish.

Keywords: Inorganic arsenic; Microwave-assisted alkaline dissolution; Anion-exchange HPLC-ICP-MS; Seafood

Preservation strategies for inorganic arsenic species in high iron, low-Eh groundwater from West Bengal, India by Andrew G. Gault; Joydeb Jana; Sudipto Chakraborty; Partha Mukherjee; Mitali Sarkar; Bibash Nath; David A. Polya; Debashis Chatterjee (pp. 347-353).

Despite the importance of accurately determining inorganic arsenic speciation in natural waters to predicting bioavailability and environmental and health impacts, there remains considerable debate about the most appropriate species preservation strategies to adopt. In particular, the high-iron, low-Eh (redox potential) shallow groundwaters in West Bengal, Bangladesh and SE Asia, the use of which for drinking and irrigation purposes has led to massive international concerns for human health, are particularly prone to changes in arsenic speciation after sampling. The effectiveness of HCl and EDTA preservation strategies has been compared and used on variably arsenic-rich West Bengali groundwater samples, analysed by ion chromatography–inductively coupled plasma–mass spectrometry (IC–ICP–MS). Immediate filtration and acidification with HCl followed by refrigerated storage was found to be the most effective strategy for minimizing the oxidation of inorganic As(III) during storage. The use of a PRP-X100 (Hamilton) column with a 20 mmol L⁻¹ NH₄H₂PO₄ as mobile phase enabled the separation of Cl⁻ from As(III), monomethylarsonic acid, dimethylarsinic acid and As(V), thereby eliminating any isobaric interference between ⁴⁰Ar³⁵Cl⁺ and ⁷⁵As⁺. The use of EDTA as a preservative, whose action is impaired by the high calcium concentrations typical of these types of groundwater, resulted in marked oxidation during storage. The use of HCl is therefore indicated for analytical methods in which chloride-rich matrices are not problematical. The groundwaters analysed by IC–ICP–MS were found to contain between 5 and 770 ng As mL⁻¹ exclusively as inorganic arsenic species. As(III)/total-As varied between 0 and 0.94.

Keywords: IC–ICP–MS; Arsenic; Speciation; Preservation; Groundwater

Mercury speciation in thawed out and refrozen fish samples by gas chromatography coupled to inductively coupled plasma mass spectrometry and atomic fluorescence spectroscopy by Petra Krystek; Rob Ritsema (pp. 354-359).

Different sub-sampling procedures were applied for the determination of mercury species (as total mercury Hg, methylmercury MeHg⁺ and inorganic mercury Hg²⁺) in frozen fish meat. Analyses were carried out by two different techniques. After the sample material was pre-treated by microwave digestion, atomic fluorescence spectroscopy (AFS) was used for the determination of total Hg. Speciation analysis was performed according to the following procedure: dissolution of sample material in tetramethylammonium hydroxide (TMAH), derivatisation with sodium tetraethylborate (NaBEt₄), extraction into isooctane and measurement with gas chromatography inductively coupled plasma mass spectrometry (GC-ICPMS) for the identification and quantification of methylmercury (MeHg⁺) and inorganic mercury (Hg²⁺). The concentration range of total Hg measured in the shark fillets is between 0.9 and 3.6 μg g⁻¹ thawed out shark fillet. Speciation analysis leads to ≥94% Hg present as MeHg⁺. Homogeneity, storage conditions and stability of analytical species and sample materials have great influence on analytical results. Sub-sampling of half-frozen/partly thawed out fish and analysis lead to significantly different concentrations, which are on average a factor of two lower.

Keywords: Methylmercury; Inorganic mercury; Speciation; Frozen fish; Shark; Sub-sampling; Atomic fluorescence spectrometry; Gas chromatography; Inductively coupled plasma mass spectrometry

Extraction of methylmercury from tissue and plant samples by acid leaching by Holger Hintelmann; Hong T. Nguyen (pp. 360-365).

A simple and efficient extraction method based on acidic leaching has been developed for measurement of methylmercury (MeHg) in benthic organisms and plant material. Methylmercury was measured by speciated isotope-dilution mass spectrometry (SIDMS), using gas chromatography interfaced with inductively coupled plasma mass spectrometry (GC–ICP–MS). Reagent concentration and digestion temperature were optimized for several alkaline and acidic extractants. Recovery was evaluated by addition of MeHg enriched with CH₃²⁰¹Hg⁺. Certified reference materials (CRM) were used to evaluate the efficiency of the procedure. The final digestion method used 5 mL of 4 mol L⁻¹ HNO₃ at 55°C to leach MeHg from tissue and plant material. The digest was further processed by aqueous phase ethylation, without interference with the ethylation step, resulting in 96±7% recovery of CH₃²⁰¹Hg⁺ from oyster tissue and 93±7% from pine needles. Methylmercury was stable in this solution for at least 1 week and measured concentrations of MeHg in CRM were statistically not different from certified values. The method was applied to real samples of benthic invertebrates and inter-laboratory comparisons were conducted using lyophilized zooplankton, chironomidae, and notonectidae samples.

Keywords: Methylmercury extraction; Zooplankton; Benthos; Pine needles; Speciated isotope dilution mass spectrometry

Electrochemical vapor generation of selenium species after online photolysis and reduction by UV-irradiation under nano TiO₂ photocatalysis and its application to selenium speciation by HPLC coupled with atomic fluorescence spectrometry by Jing Liang; Qiuquan Wang; Benli Huang (pp. 366-372).

An online UV photolysis and UV/TiO₂ photocatalysis reduction device (UV–UV/TiO₂PCRD) and an electrochemical vapor generation (ECVG) cell have been used for the first time as an interface between high-performance liquid chromatography (HPLC) and atomic fluorescence spectrometry (AFS) for selenium speciation. The newly designed ECVG cell of approximately 115 μL dead volume consists of a carbon fiber cathode and a platinum loop anode; the atomic hydrogen generated on the cathode was used to reduce selenium to vapor species for AFS determination. The noise was greatly reduced compared with that obtained by use of the UV–UV/TiO₂PCRD–KBH₄–acid interface. The detection limits obtained for seleno-DL-cystine (SeCys), selenite (Se^IV), seleno-DL-methionine (SeMet), and selenate (Se^VI) were 2.1, 2.9, 4.3, and 3.5 ng mL⁻¹, respectively. The proposed method was successfully applied to the speciation of selenium in water-soluble extracts of garlic shoots cultured with different selenium species. The results obtained suggested that UV–UV/TiO₂PCRD–ECVG should be an effective interface between HPLC and AFS for the speciation of elements amenable to vapor generation, and is superior to methods involving KBH₄.

Keywords: Selenium speciation; UV/TiO₂ photocatalysis; Electrochemical vapor generation; HPLC; AFS

Enzymatic probe sonication extraction of Se in animal-based food samples: a new perspective on sample preparation for total and Se speciation analysis by Ana I. Cabañero; Yolanda Madrid; Carmen Cámara (pp. 373-379).

This paper describes a fast, simple and novel extraction method for total selenium and selenium species determination in food samples. Parameters influencing extraction, such as sonication time, extracting media, temperature, sample mass, ultrasound amplitude and sample/enzyme mass ratio were investigated. The enzymatic hydrolysis proposed, enhanced by probe sonication, allowed the quantitative extraction of selenium in chicken muscle, liver, kidney and feed (97, 93, 95 and 102%, respectively) in 2 min, maintaining the original Se-species integrity. Total Se content of the samples was determined using inductively coupled plasma mass spectrometry. Se-species were identified and quantified using high-performance liquid chromatography in conjunction with inductively coupled plasma mass spectrometry. Chromatographic analyses were carried out under two chromatographic conditions and led to the identification of SeMet in all samples. The accuracy of the proposed method was assessed using certified reference materials as well as microwave digestion. Potential advantages of the proposed method over traditional hydrolysis are speed, simplicity and safety of the procedure.

Keywords: Selenium; Extraction; Speciation; Selenomethionine; Food

Monitoring the degradation and solubilisation of butyltin compounds during in vitro gastrointestinal digestion using “triple spike” isotope dilution GC-ICP-MS by Pablo Rodríguez-González; Jorge Ruiz Encinar; J. Ignacio García Alonso; Alfredo Sanz-Medel (pp. 380-387).

An in vitro gastrointestinal digestion approach in combination with species-specific isotope dilution analysis has been employed for the first time to study the transformation reactions as well as the solubilisation of butyltin species throughout a simulated human digestion. Different sample preparation procedures were assayed in order to avoid problems derived from lack of isotope equilibration between the endogenous and the isotopically-enriched added species. A “triple spike” approach, which can be used to calculate the corrected concentrations of mono-, di-, and tributyltin (MBT, DBT and TBT, respectively), as well as six interconversions, was employed throughout this work. In order to calculate and compare the species degradation factors, a triple spike solution containing each butyltin species enriched in a different isotope was added to the simulated gastric and intestinal fluids before the digestion procedures in the presence and in the absence of a solid biological matrix (commercial mussel tissue). Additionally, by analysing the soluble and insoluble fractions resulting from the simulated digestion of a commercial mussel tissue (gastric and gastric plus intestinal digestion), total mass balances for each butyltin compound could be derived. For this purpose, the isotopically-enriched species were added after the enzymatic digestions in order to avoid problems derived from lack of isotope equilibration. The mass balances provided information not only about the solubilisation but also about the degradation of the butyltin species during the digestion procedures. Good agreement between the degradation factors calculated under all experiments performed in this work and between those reported in previous works were obtained. The most serious degradation observed was that of DBT to produce MBT, whereas slight degradations of TBT and MBT were detected. Moreover, a worrying 61% of the original total butyltin content present in a commercial mussel tissue was found to be solubilised after complete simulated gastrointestinal digestion, with minimal degradation of TBT.

Preparation of trout liver microsomes for iron speciation in P-450 enzymes by AE–FPLC with ICP–(ORS)MS detection by Andrés Rodríguez-Cea; María Rosario Fernández de la Campa; Alfredo Sanz-Medel (pp. 388-393).

Cytochromes P-450 are members of a superfamily of hemoproteins involved in the oxidative metabolism of various physiological and xenobiotic compounds in eukaryotes and prokaryotes. The multiplicity of this group of enzymes has been widely studied by chromatographic techniques, mainly high-performance liquid chromatography (HPLC). Because these enzymes are membrane-bound proteins, sample preparation for chromatographic separation of P-450 enzymes requires a solubilization step. The sample-preparation procedures are critical, because detergents affect not only the efficiency of protein solubilization but also their further chromatographic resolution. Trout liver microsomes have been taken here as a model sample to investigate iron speciation in cytochrome P-450. Trouts were treated intraperitoneally with β-naphthoflavone, a potent inducer of some P-450 enzymes, and a microsomal suspension containing 7.4±0.1 nmol mL⁻¹ P-450 enzymes was obtained by ultracentrifugation. Lubrol PX was selected as detergent for solubilization, resulting in about 90% solubilization recovery. The solubilized cytochromes P-450 were further separated by AE–FPLC, with UV detection, or coupled to ICP–MS with an octapole reaction system, ICP–(ORS)MS (monitoring Fe signals at masses 54, 56, and 57). A sampling procedure and chromatographic conditions are developed and were successfully applied to iron speciation in trout liver P-450 enzymes. ICP–(ORS)MS detection of P-450 enzymes is Fe-specific and so will give accurate information on the prosthetic group of the protein, which can constitute an advantageous alternative to classical methods for detection of these hemoproteins.

Keywords: Iron speciation; Cytochrome P-450; Trout; Anion-exchange liquid chromatography; ICP-MS

Third international conference on trace element speciation in biomedical, nutritional and environmental sciences by Bernhard Michalke; Peter Schramel (pp. 394-396).

Uses of speciation techniques in biomonitoring for assessing human exposure to organic environmental chemicals by Larry L. Needham; Donald G. Patterson Jr.; Dana B. Barr; James Grainger; Antonia M. Calafat (pp. 397-404).

Speciation analysis has been used for many years to identify and measure different forms of a given chemical in environmental and human samples. Although the term “speciation” is generally applied to the measurement of inorganic chemicals, the term can also be applied to many measurements of organic chemicals in complex samples, such as environmental media and biological matrices. We present several examples of achieving speciation analysis by selecting the appropriate biological matrix in which to measure a specific chemical(s), by a given analytical method, for the most accurate assessment of human exposure to the environmental chemical. Much of this information and many of these techniques are transferable to the measurement of inorganic elements in environmental and biological samples.

Keywords: Speciation; Specificity; Biomonitoring; Chromatography; Organic environmental chemicals

Novel separation method for highly sensitive speciation of cancerostatic platinum compounds by HPLC–ICP–MS by S. Hann; Zs. Stefánka; K. Lenz; G. Stingeder (pp. 405-412).

A high-performance liquid chromatography–inductively coupled plasma mass spectrometry (HPLC–ICP–MS) method is presented for analysis of cisplatin, monoaquacisplatin, diaquacisplatin, carboplatin, and oxaliplatin in biological and environmental samples. Chromatographic separation was achieved on pentafluorophenylpropyl-functionalized silica gel. For cisplatin, carboplatin, and oxaliplatin limits of detection of 0.09, 0.10, and 0.15 μg L⁻¹, respectively, were calculated at m/z 194, using aqueous standard solutions. (3 μL injection volume). The method was utilized for model experiments studying the stability of carboplatin and oxaliplatin at different chloride concentrations simulating wastewater and surface water conditions. It was found that a high fraction of carboplatin is stable in ultrapure water and in solutions containing 1.5 mol L⁻¹ Cl⁻, whereas oxaliplatin degradation was increased by increasing the chloride concentration. In order to support the assessment of oxaliplatin eco-toxicology, the method was tested for speciation of patient urine. The urine sample contained more than 17 different reaction products, which demonstrates the extensive biotransformation of the compound. In a second step of the study the method was successfully evaluated for monitoring cancerostatic platinum compounds in hospital waste water.

Keywords: Cisplatin; Carboplatin; Oxaliplatin; Wastewater; Urine; Stability study

N-Arylamine derivatives of 3-hydroxy-4-pyridinones: solution studies and bioevaluation in view of Al-detoxification roles by M. Amélia Santos; Marco Gil; Sérgio Marques; Lurdes Gano; Sílvia Chaves (pp. 413-419).

A study of a series of bifunctional 3-hydroxy-4-pyridinone derivatives, containing side-chains with various alkyl-aryl-amine-amides as extra-functional groups, was conducted to assess the relevance of those groups to the Al-chelating affinity, the lipo–hydrophilic balance of the compounds, and ⁶⁷Ga biodistribution in mice, in view of their potential use as Al-decorporating agents; the results were compared with those for the drug Deferriprone. Their acid–base properties and Al-chelating affinity in aqueous solution were studied by potentiometric techniques. These ligands form very stable tris-chelated Al complexes and the non-chelating extra-groups are only responsible for small differences in the complex stability (ΔpAl≤1.2). At physiological pH the major ligand/complex species have different charges, because of the different extent of protonation of the ligands. The introduction of the different groups induces a well-balanced stepwise-like lipo–hydrophilic character (−0.2D_oct./water<+1.1). The effect of each ligand on the biodistribution of ⁶⁷Ga in overloaded mice is rapid blood clearance for all of them, but with different biodistribution patterns, namely excretion pathways and brain uptake/clearance, thus suggesting potential different clinical use.

Keywords: Hydroxypyridinones; 3-Hydroxy-4-pyridinones; Al chelators; Biodistribution; Gallium-67

Study of the lipophilicity of selenium species by Fotios N. Tsopelas; Maria Th. Ochsenkühn-Petropoulou; Anna Tsantili-Kakoulidou; Klaus-Michael Ochsenkühn (pp. 420-426).

In this work the lipophilicity of different selenium species occurring in environmental matrices and food, Se(IV), Se(VI), selenomethionine (Se-Met), selenocystamine (Se-CM), selenocystine (Se-Cyst), and dimethyl diselenide (CH₃)₂Se₂, was investigated in the octanol–water system, using the shaking flask method and detection with inductively coupled plasma–atomic emission spectrometry (ICP–AES), in order to assess their environmental fate and tendency to bioaccumulate. Polarography was also used for the electrochemically active Se species, Se(IV), Se-Cyst, Se-CM and (CH₃)₂Se₂, and the results were compared with those measured by ICP–AES. Furthermore, the influence of pH was studied by determining the logarithm of the distribution coefficient, log D, at three pH values, 5, 7, and 9, as was the impact of the marine environment on the lipophilicity profile of the six investigated Se species. The results were compared with those estimated approximately by use of PrologD software, based on the Ghose-Crippen log P (P: partition coefficient) calculation system, the only system which incorporates values—even though approximate—for the atom type of Se. Finally, from our experimental data an indicative value of the Se–Se fragment for log P prediction, for use in drug design, was estimated.

Keywords: Lipophilicity; Selenium; Selenocystamine; Selenocystine; Selenomethionine; Polarography

Measuring the solubilities of ionic liquids in water using ion-selective electrodes by Natalia V. Shvedene; Svetlana V. Borovskaya; Victor V. Sviridov; Erika R. Ismailova; Igor V. Pletnev (pp. 427-430).

Polyvinyl chloride-plasticized membrane ion-selective electrodes (ISE) based on conventional ion-exchangers have been proposed as a cheap universal tool to measure the solubilities of ionic liquids (ILs) in water. They are applicable for ILs with a wide range of solubilities in water, since the linear range of a potentiometric response spans several orders of magnitude. As an example, we have fabricated and tested ISEs for widely used alkylimidazolium ionic liquids. The aqueous solubilities of four typical ILs have been determined at 21 °C: 0.075±0.001 mol l⁻¹ (1-butyl-3-methylimidazolium, BMIm, hexafluorophosphate); 0.018±0.001 mol l⁻¹ (BMIm bis(triflylimide)); 0.054±0.007 mol l⁻¹ (1-butyl-2,3-dimethylimidazolium, BDMIm, hexafluorophosphate); 0.014±0.001 mol l⁻¹ (BDMIm bis(triflylimide)).

Keywords: Ion-selective electrodes; Ionic liquids; Solubility

Deep-UV Raman spectrometer tunable between 193 and 205 nm for structural characterization of proteins by Igor K. Lednev; Vladimir V. Ermolenkov; Wei He; Ming Xu (pp. 431-437).

A new deep-UV Raman spectrometer utilizing a laser source tunable between 193 and 205 nm has been designed, built, and characterized. Only selected wavelengths from this range have previously been accessible, by Raman shifting of the second, third, and fourth harmonics of the Nd:YAG fundamental in hydrogen. The apparatus was demonstrated to be a useful tool for characterizing hen egg white lysozyme structural rearrangements at various stages of fibril formation. High-quality deep-UV resonance Raman spectra were obtained for both a protein solution and a highly-scattering gelatinous phase formed by fibrillogenic species. In addition to amide bands, strong contribution of ν₁₂ and ring-C phenylalanine vibrational modes was observed at excitation wavelengths below 200 nm. Remarkably, the Raman cross-section of these modes revealed dramatic change of lysozyme in response to heat denaturation and fibril formation. These results indicate that phenylalanine could serve as a new deep-UV Raman probe of protein structure.

Keywords: Raman spectroscopy; protein; Amyloid fibril; Structure; Lysozyme; Phenylalanine

Microanalytical flow-through method for assessment of the bioavailability of toxic metals in environmental samples by Modupe Jimoh; Wolfgang Frenzel; Volkmar Müller (pp. 438-444).

The application of a recently proposed microanalytical flow-through system for on-line sequential extraction of heavy metals from solid samples of environmental interest is described. Using various extraction schemes (a nitric acid scheme, a two-stage extraction scheme using two reagents applied in the BCR procedure) and comparison with the common batch sequential BCR procedure, the suitability of the system for fast screening of solid environmental samples is demonstrated. By pumping leaching agents sequentially through the sample held in a micro cartridge, the different metal fractions present can be assessed in less than an hour. Method evaluation was performed using SRM 1648 urban particulate matter and BCR 701 lake sediment reference material certified for extractable metals. The need for and design of laboratory internal reference material suitable for simulating the natural (dynamic) processes of metal release into the environment is also discussed. For the first time correlation is sought between fractionation techniques and physiologically based methods for assessment of the bioaccessibility of metals in biomatrices.

Keywords: Flow-through sequential extraction; Bioavailability; Bioaccessibility; Heavy metals; Soil

Biodegradabilities of some chain oils in groundwater as determined by the respirometric BOD OxiTop method by Pekka Vähäoja; Toivo Kuokkanen; Ilkka Välimäki; Sauli Vuoti; Paavo Perämäki (pp. 445-450).

The respirometric BOD OxiTop method was used to monitor the biodegradation of different chain oils (mineral, rapeseed and tall oils) over 28 days in groundwater, as well as in standard conditions described by OECD 301 F. The aim of the study was to gather more information about the biodegradability of forestry oils in groundwater, as well as about the suitability of the automatic OxiTop method for biodegradation measurements. The BOD OxiTop method proved to be a precise and reliable technique for determining the biodegradations of different oils. Some comparative studies were also made using a traditional IR method in order to clarify the total oil concentrations. The results show that if biodegradation only is to be monitored, the OxiTop method is preferable. This is due to the influence of other reactions aside from biodegradation on total hydrocarbon concentrations when using the IR method.

Keywords: Chain oil; Groundwater; Biodegradation; BOD OxiTop method

Spectroscopic and voltammetric studies of Pefloxacin bound to calf thymus double-stranded DNA by A. Radi; M. A. EL Ries; S. Kandil (pp. 451-455).

Spectral and electrochemical studies have been carried out on the interaction of pefloxacin with calf thymus double-stranded dsDNA. The voltammetric behavior of pefloxacin was investigated at glassy carbon, carbon paste and dsDNA-modified carbon paste electrodes using cyclic voltammetry. Pefloxacin was oxidized, yielding one irreversible oxidation peak. The modification of the carbon paste surface with dsDNA allowed an accumulation process to take place for pefloxacin such that higher sensitivity was achieved compared with the bare surface. The response was characterized with respect to ionic strength, accumulation time, pefloxacin concentration, and other variables. The stripping differential pulse voltammetric response showed a linear calibration curve in the range 1.0×10⁻⁷–1.0×10⁻⁵ mol l⁻¹ with a detection limit of 5.0×10⁻⁸ mol l⁻¹ at the dsDNA modified electrode. The method was applied to the direct determination of pefloxacin in diluted urine samples.

Keywords: Spectroscopy; Voltammetry; Pefloxacin; DNA-drug interaction; DNA-modified electrode; Urine analysis

Determination of ion-pair formation constants of univalent metal–crown ether complex ions with anions in water using ion-selective electrodes: application of modified determination methods to several salts by Yoshihiro Kudo; Masaomi Wakasa; Tomomi Ito; Jun Usami; Shoichi Katsuta; Yasuyuki Takeda (pp. 456-463).

Ion-pair formation constants (mol⁻¹ dm³ unit), K_MX for a univalent metal salt (MX) and K_MLX for its ion-pair complex (ML⁺X⁻) with a crown ether (L) in water, were determined at various ionic strengths (I) and 25°C by potentiometry with ion-selective electrodes for MX=NaPic, NaMnO₄, NaBPh₄, KPic, and KMnO₄; and MLX=Na(18C6)Pic, K(18C6)Pic, and Na(18C6)BPh₄, where Pic⁻ and 18C6 denote a picrate ion and 18-crown-6 ether, respectively. Equations for analyzing I-dependence of logK_MLX and logK_MX were derived and fitted well to the I-dependence using a non-linear regression analysis. The equilibrium constants at I=0 mol dm⁻³, K_MLX° and K_MX°, were simultaneously obtained from the analysis. The experimental values of K_MLX and K_MX were only in agreement with the values calculated from K_MLX° and K_MX°, respectively, in the ranges of higher I.

Keywords: Ion-pair formation constant; In water; Crown ether complex ion; Picrates; Permanganates; ISE

Solvent extraction and extraction–voltammetric determination of phenols using room temperature ionic liquid by Kristine S. Khachatryan; Svetlana V. Smirnova; Irina I. Torocheshnikova; Natalia V. Shvedene; Andrey A. Formanovsky; Igor V. Pletnev (pp. 464-470).

The phenolic compounds phenol, 4-nitrophenol, 2,4-dinitrophenol, 2,6-dinitrophenol, 1-naphthol, 2-naphthol, and 4-chlorophenol are extracted nearly quantitatively from aqueous solution into the room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMImPF₆) in molecular form at pHK_a. Picric acid is extracted efficiently in anionic form. Recovery of pyrocatechol and resorcinol is much lower. The effect of pH, phenol concentration, and volume ratio of aqueous and organic phases were studied. Ionic liquid BMImPF₆ is shown to be suitable for extraction–voltammetric determination of phenols without back-extraction or addition of support electrolyte. The electrochemical window of BMImPF₆ at various electrodes was determined, and voltammetric oxidation of phenols and reduction of nitrophenols in BMImPF₆ was studied.

Keywords: Room temperature ionic liquid; Phenols; Liquid–liquid extraction; Voltammetry

Synthesis, characterization, and analytical application of zirconium(IV) selenoiodate, a new cation exchanger by V. K. Gupta; Premvir Singh; Nafisur Rahman (pp. 471-476).

Zirconium(IV) selenoiodates have been synthesized under a variety of conditions. The most chemically and thermally stable sample is prepared by adding a mixture of aqueous solutions of 0.1 mol L⁻¹ potassium iodate and 0.1 mol L⁻¹ sodium selenite to aqueous solution of 0.1 mol L⁻¹ zirconium(IV) oxychloride. Its ion-exchange capacity for K⁺ and Pb²⁺ was found to be 3.20 and 2.35 meq g⁻¹ dry exchanger, respectively. The material has been characterized on the basis of chemical composition, pH titration, and thermogravimetric analysis. The effect on the exchange capacity of drying the exchanger at different temperatures has also been studied. The analytical importance of the material has been established by quantitative separation of Pb²⁺ from other metal ions.

Keywords: Synthesis; Characterization; Zirconium(IV) selenoiodate; Cation exchanger

Microsynthesis and electron ionisation mass spectrometric analysis of chemical weapons convention (CWC)-related O,O-dialkyl-N,N-dialkylphosphoramidates by Meehir Palit; Deepak Pardasani; A. K. Gupta; Purushottam Shakya; D. K. Dubey (pp. 477-486).

The paper describes microsynthesis and GC/EIMS analysis of O,O-dialkyl-N,N-dialkylphosphoramidates (DADAPs). DADAPs belong to schedule 2B6 category of chemical weapons convention (CWC), as they are important markers of the chemical warfare agent Tabun and its analogues. The study was undertaken to develop a spectral database of DADAPs for verification of CWC. The reported synthetic strategy can be adopted to prepare several analogues of DADAPs simultaneously and rapidly during official proficiency tests, for the unambiguous identification of analytes within a short period. Based on the EIMS data of more than 60 compounds, fragmentation routes are proposed which explain the formation of most of the characteristic fragment ions. Subtle differences in EIMS of isomeric DADAPs are discussed to facilitate their identification.

Keywords: Chemical warfare agent; Tabun; Nerve agent; Chemical weapons convention (CWC); Microsynthesis; Markers; EIMS; Phosphoramidates

Discrimination of three tobacco types (Burley, Virginia and Oriental) by pyrolysis single-photon ionisation–time-of-flight mass spectrometry and advanced statistical methods by T. Adam; T. Ferge; S. Mitschke; T. Streibel; R. R. Baker; R. Zimmermann (pp. 487-499).

Pyrolysis single-photon ionisation (SPI)–time-of-flight mass spectrometry (TOFMS) and statistical analysis techniques have been applied to differentiate three major tobacco types, Burley, Virginia and Oriental, by means of the gas phase. SPI is known as a soft ionisation technique that allows fast and comprehensive on-line monitoring of a large variety of aliphatic and aromatic substances without fragmentation of the molecule ions. The tobacco samples were pyrolysed at 800°C in a nitrogen atmosphere. The resulting pyrolysis gas contained signals from more than 70 masses between m/z 5 and 170. Mass spectra obtained were analysed by principal component analysis (PCA) and linear discriminant analysis (LDA) to distinguish between different tobacco types. Prior variable reduction of the data set was carried out by calculation of the Fisher ratios. Results achieved give information about chemical composition and characteristics of the smoke derived from each tobacco type and enable conclusions on plant cultivation to be drawn. Based on LDA, a model for tobacco type recognition of unknown samples was established, which was cross-checked by additional measurements of each tobacco type. Furthermore, first results on the recognition of tobacco mixtures based on principal component regression (PCR) are presented.

Keywords: Pyrolysis; Tobacco; Single-photon ionisation; Multivariate analysis

Glucose biosensor based on glucose oxidase immobilized in sol–gel chitosan/silica hybrid composite film on Prussian blue modified glass carbon electrode by Xue-Cai Tan; Yuan-Xin Tian; Pei-Xiang Cai; Xiao-Yong Zou (pp. 500-507).

An improved amperometric glucose biosensor based on glucose oxidase immobilized in sol–gel chitosan/silica hybrid composite film, which was prepared from chitosan (CS) and methyltrimethoxysilane (MTOS), on the surface of Prussian blue (PB)-modified glass carbon electrode was developed. The film was characterized by FT-IR. Effects of some experimental variables such as ratio of CS to silica, buffer pH, temperature, and applied potential on the current response of the biosensor were investigated. The biosensor fabricated under optimal conditions had a linear response to glucose over the range 5.0×10⁻⁵ to 2.6×10⁻² M with a correlation coefficient of 0.9948 and a detection limit of 8.0×10⁻⁶ M based on S/N =3. The biosensor had a fast response time of less than 10 s, a high sensitivity of 420 nA mM⁻¹, a long-term stability of over 60 days, and a good selectivity. The apparent Michaelis–Menten constant K_m was found to be 3.2×10⁻³ M. The activation energy for enzymatic reaction was calculated to be 21.9 kJ mol⁻¹. This method has been used to determine the glucose concentration in real human blood samples.

Keywords: Sol–gel; Chitosan/silica hybrid composite film; Glucose biosensor; Prussian blue

Determination of selected polycyclic aromatic hydrocarbons and oxygenated polycyclic aromatic hydrocarbons in aerosol samples by high-performance liquid chromatography and liquid chromatography–tandem mass spectrometry by Jutta Lintelmann; Karin Fischer; Erwin Karg; Andreas Schröppel (pp. 508-519).

Fine and ultrafine particles are probably responsible for numerous health effects, but it is still unclear whether and to what extent the particle itself or organic compounds adsorbed or condensed on the particle are responsible for the effects observed. One important class of particle-bound substances are the polycyclic aromatic hydrocarbons (PAH) and their oxygenated derivatives. To improve the tools used for chemical characterization of particulate matter analytical methods for the determination of PAH and oxygenated PAH in aerosol samples of different origin have been developed and optimized. PAH on high-volume filters and on soot aerosols were analyzed by using accelerated solvent extraction for extraction and high-performance liquid chromatography with fluorescence detection for separation and quantification. Total PAH concentrations were in the range 0.3–9.3 ng m⁻³. For analysis of selected oxygenated PAH on high-volume filters a liquid chromatography–tandem mass spectrometric method was developed and optimized. Preliminary investigations showed that oxygenated PAH at pg m⁻³ concentrations can be determined.

Keywords: PAH; Oxygenated PAH LC–MS–MS; LC–MS–MS; ASE; Particulate matter

Polarographic and voltammetric determination of trace amounts of 2-nitronaphthalene by Karolina Pecková; Jiří Barek; Josino Costa Moreira; Jiří Zima (pp. 520-525).

The polarographic behaviour of 2-nitronaphthalene was investigated by DC tast polarography (DCTP) and differential pulse polarography (DPP), both at a dropping mercury electrode, and differential pulse voltammetry and adsorptive stripping voltammetry, both at a hanging mercury drop electrode. Optimum conditions have been found for the determination of 2-nitronaphthalene by the given methods in the concentration ranges of 2×10⁻⁶–1×10⁻⁴, 2×10⁻⁷–1×10⁻⁴, 1×10⁻⁸–1×10⁻⁴ and 2×10⁻⁹–1×10⁻⁸ M, respectively. Practical applicability of these techniques was demonstrated by the determination of 2-nitronaphthalene in drinking and river water after its preliminary separation and preconcentration using liquid–liquid and solid-phase extraction with limits of determination of 3×10⁻¹⁰ M (drinking water) and 3×10⁻⁹ M (river water).

Keywords: DC tast polarography; Differential pulse polarography; Differential pulse voltammetry; Adsorptive stripping voltammetry; 2-Nitronaphthalene

Ultra-sensitive fully automated immunoassay for detection of propanil in aqueous samples: steps of progress toward sub-nanogram per liter detection by Jens Tschmelak; Guenther Proll; Guenter Gauglitz (pp. 526-526).

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Analytical and Bioanalytical Chemistry (v.381, #2)

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Analytical and Bioanalytical Chemistry (v.381, #2)