Showing papers in "Fresenius Journal of Analytical Chemistry in 1998"
TL;DR: The execution of stability studies using “isochronous” measurements only requires repeatability conditions, whereas classical designs require both repeatability and long term reproducibility conditions, which allows the quality of results to be improved.
Abstract: An alternative method for stability testing of candidate certified reference materials (CRMs) utilizing “isochronous” measurements based on a storage design (storing samples at different temperatures for different time periods), which allows all measurements to be done at the same time, i.e. at the end of the study, is compared to “classical” designs of stability studies using reference time or reference temperature. The execution of stability studies using “isochronous” measurements only requires repeatability conditions, whereas classical designs require both repeatability and long term reproducibility conditions. Consequently, the new design allows the quality of results to be improved.
236 citations
TL;DR: An analytical method has been developed which allows the determination of 22 different neutral and weakly basic drugs belonging to several different medicinal classes like antiphlogistics, betablockers, β2-sympathomimetics, lipid regulators, antiepileptic agents, psychiatric drugs and vasodilators in waste water as well as in river and drinking water.
Abstract: An analytical method has been developed which allows the determination of 22 different neutral and weakly basic drugs belonging to several different medicinal classes like antiphlogistics, betablockers, β2-sympathomimetics, lipid regulators, antiepileptic agents, psychiatric drugs and vasodilators in waste water as well as in river and drinking water. A method including solid phase extraction, derivatization by silylation and detection by GC/MS permits detection down to 5 ng/L. The recovery rates mostly exceeded 70%. However, the determination of phenazone, carbamazepine, cyclophosphamide, ifosfamide and pentoxiphylline is frequently disturbed by organic co-extractants in real samples of rivers and waste waters. Therefore, a time saving alternative method has been developed, combining solid phase extraction (as an enrichment step) together with detection by LC-electrospray/MS/MS allowing the measurement of 5 neutral drugs. Detection limits down to 10 ng/L have been achieved even for organically highly contaminated waters like sewage treatment plant effluents.
156 citations
TL;DR: In this paper, the authors provide a framework for classifying such sensors and to assist a designer in selecting the most suitable detection techniques and waveguide arrangements, based on the five parameters that completely describe a light wave: amplitude, wavelength, phase, polarization state and time-dependent waveform.
Abstract: Current concepts for chemical and biochemical sensing based on detection with optical waveguides are reviewed The goals are to provide a framework for classifying such sensors and to assist a designer in selecting the most suitable detection techniques and waveguide arrangements Sensor designs are categorized on the basis of the five parameters that completely describe a light wave: its amplitude, wavelength, phase, polarization state and time-dependent waveform In the fabrication of a successful sensor, the physical or chemical property of the determined species and the particular light wave parameter to detect it should be selected with care since they jointly dictate the sensitivity, stability, selectivity and accuracy of the eventual measurement The principle of operation, the nature or the detected optical signal, instrumental requirements for practical applications, and associated problems are analyzed for each category of sensors Two sorts of sensors are considered: those based on direct spectroscopic detection of the analyte, and those in which the analyte is determined indirectly through use of an analyte-sensitive reagent Key areas of recent study, useful practical applications, and trends in future development of optical waveguide chemical and biochemical sensors are considered
137 citations
TL;DR: In this article, Nanocrystalline thick-film SnO2 sensors with different dopants were fabricated by an optimized screen printing process and subsequent annealing, and they were used as starting materials which were prepared by a wet chemical process from SnCl4.
Abstract: Nanocrystalline thick-film SnO2 sensors with different dopants were fabricated by an optimized screen printing process and subsequent annealing. Powders were used as starting materials which were prepared by a wet chemical process from SnCl4. Microanalysis was performed of both, the precursors and the final sensor materials with their different annealing conditions. Gas sensing tests with CO, CH4 and NO2 in air with controlled humidity were correlated with results from X-ray photoemission spectroscopy (XPS), Raman spectroscopy and transmission electron microscopy (TEM). As an interesting result, the distribution of the transition metal dopants Pd and Pt (as deduced from TEM and XPS data) rules out the existence of metallic clusters or even atoms in the metallic state at the surface. This finding does not allow to explain the sensor effects on SnO2 based materials as usually done by means of spill-over effects or Fermi energy control.
128 citations
TL;DR: In this paper, the analytical methods and techniques most frequently described in the literature for the determination of antimony species in waters (and possibly in other matrices) at ultratrace levels are summarized and discussed.
Abstract: This review summarizes and discusses the analytical methods and techniques most frequently described in the literature for the determination of antimony species in waters (and possibly in other matrices) at ultratrace levels. The analytical methods for the separation and/or selective determination of Sb species fall into four main categories: 1. Chemical methods, which include such extraction techniques as: liquid-liquid and liquid-solid extraction, selective hydride generation and coprecipitation methods. 2. Chromatographic methods, which also includes a discussion of hyphenated techniques with different detectors. 3. Electrochemical methods based on the use of electrochemical detectors. 4. Kinetic methods The state-of-the-art of the main applications in waters and environmental samples and future trends are also reviewed.
119 citations
TL;DR: In this article, the electronic tongue is used for integral qualitative analysis of beverages and for quantitative analysis of biological liquids and solutions, containing heavy metals, using an array of non-specific (non-selective) potentiometric chemical sensors.
Abstract: Development, recent historical background and analytical applications of promising sensor instruments based on sensor arrays with data processing by pattern recognition methods have been described. Attention is paid to the “electronic tongue” based on an array of original non-specific (non-selective) potentiometric chemical sensors. Application results for integral qualitative analysis of beverages and for quantitative analysis of biological liquids and solutions, containing heavy metals are reported. Discriminating abilities and precision obtained allow to consider “electronic tongue” as a perspective analytical tool.
116 citations
TL;DR: In this paper, the authors describe the development of various acid sample decomposition methods, as well as an extraction (leaching) method and compares them with the Schoniger Combustion technique.
Abstract: This paper describes the development of various new acid sample decomposition methods, as well as an extraction (leaching) method and compares them with the “Schoniger Combustion” technique. The methods have been developed as sample preparation techniques for iodine determination in biological materials, especially in solid samples. ICP-MS (inductively coupled plasma mass spectrometry) and a catalytic technique are employed and discussed for the final determination of iodine concentrations. Accuracy and reliability of the different analytical methods are shown in the examples of different CRMs (certified reference materials) available for iodine. The results of an interlaboratory comparison are specifically presented for the extraction (leaching) method.
112 citations
TL;DR: In this paper, an analytical approach is presented that utilizes CSV (cathodic stripping voltammetry) determination of Pt and Rh in polluted common grass, successfully discriminating trends in the imission situation.
Abstract: An analytical approach is presented that utilizes CSV (cathodic stripping voltammetry) determination of Pt and Rh in polluted common grass, successfully discriminating trends in the imission situation. A sampling strategy was developed leading to clear spatial trends. It is shown that additional detection of Rh helps to confirm accuracy even of peak Pt concentrations. Applicability and reliability of CSV Rh (and Pt) detection is proven during comparative measurements in other laboratories. Independent instrumental methods (ICP-MS, docimasy) confirmed CSV results, particularly in the case of Rh. In 1997, concentrations of Pt and Rh in grass samples were found to be 2.7 times higher than in 1994, and in dust samples 3.9 times higher than in 1994, respectively. Percentage of cars equipped with catalytic converters, on the other hand, was 2.4 times higher in 1997 compared with 1994. Some of the first rhodium concentrations in environmental samples are reported.
105 citations
TL;DR: In this paper, the authors describe the interlaboratory testing of EDTA and DTPA extraction procedures for soil analysis, followed by the preparation of a calcareous soil reference material (CRM 600), the homogeneity and stability studies and the analytical work performed for the certification of the EDTA-and DTPA- extractable contents of some trace metals (following the standardized extraction procedures).
Abstract: Single extraction tests are commonly used to study the eco-toxicity and mobility of metals in soils, e.g. to assess the bioavailable metal fraction (and thus to estimate the related phyto-toxic and nutritional deficiency effects) and the environmentally accessible trace metals upon disposal of e.g. sediment on to a soil (e.g. contamination of ground waters). However, the lack of uniformity in the different procedures does not allow the results to be compared worldwide nor the procedures to be validated. This paper describes the interlaboratory testing of EDTA- and DTPA-extraction procedures for soil analysis, followed by the preparation of a calcareous soil reference material (CRM 600), the homogeneity and stability studies and the analytical work performed for the certification of the EDTA- and DTPA- extractable contents of some trace metals (following the standardized extraction procedures).
103 citations
TL;DR: In this article, the authors combine molecular imprinting with mass-sensitive transducers to increase the sensitivity of sensor material synthesis with inert analytes acting as molecular templates, where the remaining imprint allows the molecular recognition of an analyte due to host-guest-interactions.
Abstract: The technique of molecular imprinting – a novel tool of sensor material synthesis – can be successfully combined with mass-sensitive transducers. Imprinted polymers are prepared in presence of inert analytes acting as molecular templates. The remaining imprint allows the molecular recognition of an analyte due to host-guest-interactions. The sensor properties of devices coated with imprint polymers can be tuned to the analyte by variation of the polymerization solvent and the amount of cross-linker added. A further sensitivity enhancement can be achieved by rising the resonant frequencies of QMBs and SAW resonators, since the signal to noise-ratio increases in an approximately linear manner with the oscillation frequency.
96 citations
TL;DR: A trace analytical procedure for the cytostatic drugs carmustine, chlorambucil, cisplatin, cyclophosphamide, cytarabine, etoposide, 5-fluorouracil, melphalan, methotrexate, and vinblastine was developed in this paper.
Abstract: A trace analytical procedure for the cytostatic drugs carmustine, chlorambucil, cisplatin, cyclophosphamide, cytarabine, etoposide, 5-fluorouracil, melphalan, methotrexate, and vinblastine was developed in order to evaluate the environmental hazards of these drugs in clinical waste water and sewage treatment plants. The analysis was performed using solid phase extraction with subsequent HPLC separation and quantitative determination by gradient elution techniques with DAD and fluorescence detection. Detection limits after the clean-up and enrichment procedure vary from 0.002 to 0.2 mg/L. A simulation of the degradation processes under conditions as close as possible to those in a real sewage plant showed that cisplatin and cyclophosphamide are not biodegradable, but cytarabine and 5-fluorouracil are biodegradable in different magnitudes. The biodegradation process of methotrexate is combined with the generation of the toxic and persistent degradation product 7-hydroxymethotrexate.
TL;DR: In this paper, a fiber optic probe for NIR-FT-Raman spectroscopy was used, which allows sterilization and the prevention of hazards due to laser radiation and makes in vivo measurements possible.
Abstract: There is a vast demand for in vivo methods for the detection of skin cancer, one of the most dangerous skin lesions. Use of near infrared Fourier transform (NIR-FT)-Raman spectroscopy virtually eliminates the fluorescence of the normal cell constituents and provides a signal to noise ratio, rSN, large enough to successfully evaluate the spectra using chemometric methods. A novel fiber optic probe for NIR-FT-Raman spectroscopy was used, which allows sterilization and the prevention of hazards due to laser radiation and makes in vivo measurements possible. The Raman spectra of normal skin are dominated by the connective tissue, mainly collagen type I. The Raman spectra of skin with inflammatory diseases show an increased lipid and water content. Kaposi sarcomas show typical features of tumors mainly in the amide III and the protein backbone range. A clear separation of Raman spectra of normal skin from those of benign and malignant neoplasms can be achieved by cluster analysis. However, the unequivocal diagnosis of skin cancer needs investigation of a larger number of more defined skin samples, taking into consideration the concurrent appearance of different skin symptoms like coloring and inflammation.
TL;DR: In this article, an on-line hyphenation of reversed phase high-performance liquid chromatography (RP-HPLC) with inductively coupled plasma-mass spectrometry (ICP-MS) is applied, using an ultrasonic nebuliser combined with a membrane desolvator as the interface.
Abstract: 1. An on-line hyphenation of reversed phase high-performance liquid chromatography (RP-HPLC) with inductively coupled plasma-mass spectrometry (ICP-MS) is applied, using an ultrasonic nebuliser combined with a membrane desolvator as the interface. Thus, organic solvents (e.g. methanol, hexane) or gradients (e.g. methanol/water) as well as aqueous NaHCO3/NaCl mixtures can be directly used without influence on the plasma. The high resolution power of HPLC enables the separation of Pt-species, whereas ICP-MS is taken for element specific detection with low detection limits. 2. Additionally, a powerful on-line coupling of capillary electrophoresis (CE) and ICP-MS [1, 2] was used for platinum speciation in parallel. With these two methods, independent from each other, first characterisation is achieved about the nature of Pt species formed by interaction with a soil. Aqueous extracts of a clay-like humic soil, treated with a Pt contaminated tunnel dust and Pt model compounds [3] were examined to elucidate transformation processes of Pt-species in a soil.
TL;DR: In this article, a rapid, inexpensive and solvent-free method for the simultaneous determination of the polyamide plasticizer N-butylbenzenesulfonamide (NBBS) and the widely used pharmaceutical Ibuprofen by solid phase microextraction (SPME) combined with gas chromatography/mass spectrometry (GC/MSD) in wastewater samples was developed.
Abstract: A rapid, inexpensive and solvent-free method for the simultaneous determination of the polyamide plasticizer N-butylbenzenesulfonamide (NBBS) and the widely used pharmaceutical Ibuprofen by solid phase microextraction (SPME) combined with gas chromatography/mass spectrometry (GC/MSD) in wastewater samples was developed. Besides the optimized analytical conditions, results of investigations with varying analytical parameters are reported. Problems, which may occur during the analytical procedure (e.g. salt deposits, adsorption phenomena, carry-over), are discussed. For the determination of Ibuprofen, it is important to carry out the extraction under acidic conditions with sufficiently buffered samples; the GC/MSD system must be very clean and well maintained. SPME allows an extraction of Ibuprofen without derivatization of its carboxylic group. For quantification in complex matrices, the standard addition technique is necessary. Limit of detection and limit of determination are 0.1 μg/L for both analytes. NBBS and Ibuprofen were detected in several raw and treated wastewater samples from municipal wastewater treatment plants in the range from < 0.1 to 3.5 μg/L.
TL;DR: The analytical literature about chromium speciation in solid samples has been surveyed in this article, where the methodologies to do speciation of chromium in solids after sample pretreatment are discussed, through consideration of the types of samples and their dissolution.
Abstract: The analytical literature about chromium speciation in solid samples has been surveyed. From 451 articles published on the speciation of chromium from 1983 to 1997, the methodologies to do speciation in solids after sample pretreatment are discussed, through consideration of the types of samples and their dissolution, the analytical techniques employed for chromium measurement, and the figures of merit of the 86 papers reported in the Analytical Abstracts data base.
TL;DR: Microwave assisted EPA method 3051 for nitric acid leaching of environmentally key elements from sediments, soils, and sludges was tested, and the influence of leaching temperature and time on element recovery for an estuarine sediment (CRM 277) was investigated as discussed by the authors.
Abstract: Microwave-assisted EPA method 3051 for nitric acid leaching of environmentally key elements from sediments, soils, and sludges was tested, and the influence of leaching temperature and time on element recovery for an estuarine sediment (CRM 277) was investigated. The extraction efficiencies for four certified reference materials applying EPA method 3051, an optimized nitric acid procedure, and an aqua regia (HCl/HNO3 3:1) procedure were compared. Digestions were carried out in a high-pressure microwave system offering simultaneous temperature and pressure control for all digestion vessels employed. Eight elements (Cd, Co, Cr, Cu, Hg, Ni, Pb, and Zn) were determined by ICP-AES and ICP-MS. Extraction efficiency strongly depended on the applied leaching parameters and varied for certain elements among different materials when a nitric acid procedure was applied. In general, element recoveries obtained from the aqua regia procedure were superior to those obtained from nitric acid procedures and showed good agreement with the 95% confidence interval of the certified value for most of the elements investigated.
TL;DR: In this article, the authors developed a new method for the simultaneous determination of the main arsenic species so far detected in urine: arsenite (As(III)), arsenate (As (V)), methylarsonic acid (MA), dimethylarsinic acid (DMA), and arsenobetaine (AsB).
Abstract: Urinary arsenic speciation is considered to be an effective procedure to differentiate between toxic inorganic and less toxic organic arsenic exposure. The aim of the present work was to develop a new method for the simultaneous determination of the main arsenic species so far detected in urine: arsenite (As(III)), arsenate (As(V)), methylarsonic acid (MA), dimethylarsinic acid (DMA), and arsenobetaine (AsB). The method is based on anion exchange HPLC coupled on-line to an inductively coupled plasma mass spectrometer (ICP-MS) for element specific detection. Experimental parameters, such as column type and composition of the mobile phases were optimized in order to get best separation, little matrix interferences, lowest detection limits, and short total times of analyses. Best chromatographic conditions were obtained by using a Dionex AS14 anion exchange column and a gradient elution with tetramethylammonium hydroxide and ammonium carbonate as eluting compounds. The detection limits (3 σ) were found to be in the sub μg L–1 range. The method was applied to analyze different urine samples from persons with and without consumption of seafood. To avoid significant matrix influences, samples (24 h urine) had to be diluted 1 : 5 with water and were filtered through a 0.45 μm filter prior to analyses. Special attention was focused on the validation of the method according to the regulations of the “Deutsche Forschungsgemeinschaft” (DFG) for the analyses of hazardous substances in biological materials.
TL;DR: In this paper, a dual stage preconcentration system based on flow injection on-line ion exchange and solvent extraction has been developed for flame atomic absorption spectrometry, where lead is taken as a model trace element.
Abstract: A dual stage preconcentration system based on flow injection on-line ion-exchange and solvent-extraction has been developed for flame atomic absorption spectrometry. Lead is taken as a model trace element. A column packed with Amberlite IRC-718 cation exchanger is incorporated into the FI manifold. The analyte is retained on the column by time-based sample loading and eluted by 1 mol/L HNO3. The eluate is subsequently merged with potassium iodide and tetrabutylammonium bromide (TBABr), and isobutyl methyl ketone (IBMK). Lead is extracted on-line into IBMK as the ion-pair formed between the iodoplumbate anion and tetrabutylammonium cation. The organic phase is separated from the aqueous phase by a gravity phase separator. 50 μL of concentrate is introduced into the nebulizer-burner system of the spectrometer. An enhancement factor of 550 is achieved with a 30 mL sample consumption at a sampling frequency of 30/h. The precision (relative standard deviation) is 2.4% at 10 μg/L level and the detection limit is 0.3 μg/L (3 σ). The method was successfully applied to the determination of lead in water samples.
TL;DR: The desorption of the metal, by fluxing a chelating solution, restored the metal binding capacity of the cells, thus affording the multiple use of the same biomass in the remediation treatment.
Abstract: Microbial biomass provides available ligand groups on which metal ions bind by different mechanisms. Biosorption of these elements from aqueous solutions represents a remediation technology suitable for the treatment of metal-contaminated effluents. The purpose of the present investigation was the assessment of the capability of Brevibacterium sp. cells to remove bivalent ions, when present alone or in pairs, from aqueous solutions, using immobilized polyacrylamide cells of the microorganism in a flow-through system. The biosorption capacity of Brevibacterium cells was studied for lead, cadmium and copper. The metal cell binding capacity followed the order Cu > Pb > Cd, based on estimated qmax. These values, expressed as mmol metal/g dry weight cells, were 0.54 for Cu, 0.36 for Pb and 0.14 for Cd. Polyacrylamide-gel immobilized cells were effective in Pb, Cu and Cd removal. Lead removal was not affected by the presence of Cd and Cu; lead instead inhibited Cd and Cu removal. The desorption of the metal, by fluxing a chelating solution, restored the metal binding capacity of the cells, thus affording the multiple use of the same biomass in the remediation treatment.
TL;DR: In this paper, gas chromatographic and liquid chromatogram methods for the investigation of phenylarsenic compounds are presented. But they do not consider the use of liquid chromatography for the detection of ADAMSITE.
Abstract: Gas chromatographic (GC) and liquid chromatographic methods for the investigation of phenylarsenic compounds are presented. With gas chromatography using an electron capture detector (ECD), the chemical warfare agents PFIFFIKUS, CLARK I and CLARK II can be detected. After derivatization with mercaptans and dimercaptans the sum of diphenylarsenic compounds resp. phenylarsenic and phenylarsonic compounds can be detected as the mercapto resp. dimercapto derivatives. High performance liquid chromatography (HPLC) analysis may be used for the detection of triphenylarsenic compounds and ADAMSITE.
TL;DR: The NIST Certificate of Analysis (CSA) is the best estimate of the true concentration of an element and is not expected to deviate from that concentration by more than the stated uncertainty.
Abstract: The National Institute of Standards and Technology (NIST, formerly the National Bureau of Standards or NBS) has produced numerous Standard Reference Materials (SRM) for use in biological and environmental analytical chemistry. The value listed on the “NIST Certificate of Analysis” is the present best estimate of the “true” concentration of that element and is not expected to deviate from that concentration by more than the stated uncertainty. However, NIST does not certify the elemental concentration of every constituent and the number of elements reported in the NIST programs tends to be limited.
TL;DR: In this article, a new method for the separation of organic antimony as trimethylantimony dichloride (TMSbCl2) and inorganic Sb(V) and Sb (III) by using anion exchange high-performance liquid chromatography coupled with inductively-coupled plasma mass spectrometry (ICP-MS) is presented.
Abstract: A new method for the separation of organic antimony as trimethylantimony dichloride (TMSbCl2) and inorganic Sb(V) and Sb(III) by using anion exchange high-performance liquid chromatography coupled with inductively-coupled plasma mass spectrometry (ICP-MS) is presented. In comparison with previous work the detection limits for both species were significantly decreased, down to 5 ngL–1, mainly by avoiding any contamination from the chromatographic device. Using an ultrasonic nebulizer (USN) improved the detection limits for inorganic Sb species, but was useless for the HPLC method due to problems in the recovery of the TMSbCl2. Matrix interferences of the chromatographic determination were studied in detail and the method was applied to environmental samples assumed to contain organic antimony species. Additionally, the molecular structure of the TMSbCl2 in solution was studied by using electrospray-ionization mass spectrometry (ESI-MS) showing that this species occurs most probably as [TMSbOH]+ in aqueous solutions.
TL;DR: In this article, an ion pair chromatographic method with ICP-MS detection for the separation of selenoamino acid standards potentially present in real samples is given.
Abstract: Consumption of selenium enriched plants or yeast-based nutritional supplements has been reported to provide anticarcinogenic benefits which are selenium compound dependent. Separation and identification of these selenium compounds is critical to understand the activity. Plants and yeast convert inorganic selenium in the soil or growth media into organoselenium compounds, probably following a route similar to the sulfur assimilatory pathway. Non-volatile selenium compounds produced include selenoamino acids, some of which have shown anticarcinogenic activity. Volatile compounds produced by chemical reaction of involatile precursors have also been found. An ion pair chromatographic method with ICP-MS detection for the separation of selenoamino acid standards potentially present in real samples is given. The method allows separation of selenoamino acids including such analytes as the cis-trans isomers of Se-1-propenyl-dl-selenocysteine. The method also provides the capability of determining the presence of selenoxides and possibly selenones, and tracking of other functionalities and reactions by selective derivatization. Alternatively, selenoamino acids are treated with ethylchloroformate to produce stable volatile derivatives which are amenable to GC separation with element specific atomic emission detection (GC-AED). Results of total selenium determination and speciation of selenium enriched yeast-based nutritional supplements, selenium enriched allium vegetables and bioremediation samples are presented.
TL;DR: A review with 159 references is presented in this article on the applications of adsorptive stripping voltammetry (AdSV) for determining trace metal ions in different environmental samples (e.g. water, soil, plant, biological fluids).
Abstract: A review with 159 references is presented on the applications of adsorptive stripping voltammetry (AdSV) for determining trace metal ions in different environmental samples (e.g. water, soil, plant, biological fluids). The analytical applications of AdSV to biologically active organic compounds (e.g. pharmaceuticals, pesticides, biomolecules) are also discussed.
TL;DR: In this paper, a method for the determination of hydrogen peroxide and several organic peroxides by high-performance liquid chromatography with post-column UV irradiation, derivatization and fluorescence detection is described.
Abstract: A method for the determination of hydrogen peroxide and several organic peroxides by high-performance liquid chromatography with post-column UV irradiation, derivatization and fluorescence detection is described. By means of post-column UV irradiation in the presence of water organic peroxides are converted into hydrogen peroxide and organic hydroperoxides, which react rapidly with the post-column derivatization agent p-hydroxyphenylacetic acid (PHPAA) under catalysis of horseradish peroxidase to yield the fluorescent PHPAA dimer that is detected at excitation and emission wavelengths of 285 and 400 nm, respectively. The detection limit for hydrogen peroxide is 14 ng/mL, for organic peroxides between 34 ng/mL and 5 μg/mL. No interference by other compounds was observed when their concentrations were below 10 mg/mL except ethers and phenols.
TL;DR: In this article, the effect of the O 2 and H 2 O content on the oxidation behavior of the 9%Cr steel P91 was studied in the temperature range of 600-800°C.
Abstract: The effect of the O 2 and H 2 O content on the oxidation behavior of the 9%Cr steel P91 was studied in the temperature range of 600-800°C. The oxidation rates under the various experimental conditions were determined by in-situ thermogravimetry. In dry oxygen a protective scale growth occurs with an oxidation rate controlled by diffusion in the scale. In presence of water vapor, after an incubation period, the scales become non-protective, as a result of a change of the oxidation limiting process. The water vapor effect is especially apparent in the temperature range of 600-700°C, whereas at higher temperatures hardly any effect was found. The destruction of the protective scale by water vapor does not only depend on the H 2 O content but also on the H 2 O/O 2 -ratio.
TL;DR: In this article, a fully automated system for the direct determination of methylmercury (MeHg), ethylmercure (EtHg, PhHg and inorganic mercury (Hg(II)) at the ng/L level is described.
Abstract: A fully automated system for the direct determination of methylmercury (MeHg), ethylmercury (EtHg), phenylmercury (PhHg), and inorganic mercury (Hg(II)) at the ng/L level is described. It is based on solid phase extraction preconcentration incorporated in a flow injection (FI) system, high performance liquid chromatography (HPLC) separation, reduction combined with thermolysis and determination by cold vapour atomic absorption spectrometry (CVAAS). For preconcentration a microcolumn of bonded silica with octadecyl functional groups (C18 reversed phase material) was used as a sorbent for the mercury complexes formed on-line with ammonium pyrrolidine dithiocarbamate. Retained mercury species are eluted with a methanol-acetonitrile-water mixture and subjected to separation on an octadecylsilane (ODS) column before determination by CVAAS. The sensitivity of organo-mercury determination could be improved by using NaBH4 as a reductant combined with a thermolysis step. In order to perform on-line measurements the preconcentration microcolumn was mounted in a pressure-tight casing. Limits of detection for MeHg, EtHg, PhHg and Hg(II) employing a sample volume of 58.5 mL were 9, 6, 10 and 5 ng/L, respectively. The relative standard deviation (RSD) calculated from 9 repeated measurements was found to be 3.6%, 5.5%, 10.4% and 7.6% for MeHg, EtHg, PhHg and Hg(II), respectively. Finally, the application of this method for speciation of mercury in fish and human urine is described.
TL;DR: In this article, the status, requirements, and potentials of CE-ICP-MS are discussed, as well as the features of electrospray ion sources that can be incorporated in CE-ICP-MS and the potential for microfabricated CE.
Abstract: This report focuses on the status, requirements, and potentials of CE-ICP-MS. The ultimate goal of a viable CE-ICP-MS system is to obtain quantitative elemental speciation information and isotopic ratio data for practical biological and environmental metal containing compounds. To make use of the CE separation features, the CE analyte must be introduced efficiently into the ICP. For practical samples, pre- and post-separation enrichment techniques probably are required. The features of electrospray ion sources that can be incorporated in CE-ICP-MS and the potential for microfabricated CE are discussed.
TL;DR: A flow injection on-line sorption preconcentration method for the electrothermal AAS determination of platinum has been developed in this paper, where pyrrolidine dithiocarbamate complexes of either Pt4+ or Pt2+, formed in 0.7 mol L−1 HNO3, are on-online adsorbed on the inner walls of a PTFE knotted reactor and subsequently eluted with methanol.
Abstract: A flow injection on-line sorption preconcentration method for the electrothermal AAS determination of platinum has been developed. The pyrrolidine dithiocarbamate complexes of either Pt4+ or Pt2+, formed in 0.7 mol L–1 HNO3, are on-line adsorbed on the inner walls of a PTFE knotted reactor and subsequently eluted with methanol. An enhancement factor of 112 and a detection limit (3 σ) of 10 ng L–1 along with a sampling frequency of 21 h–1 are achieved with a 90 s preconcentration time at a sample flow rate of 8.8 mL min–1. The relative standard deviation is 2.5% for 0.4 μg L–1 Pt. The method has been applied to the determination of platinum in blood samples.
TL;DR: In this paper, the extraction of wine aroma compounds was studied by direct-SPME (DI/SPME), headspaceSPME and multiple-headspace extraction (MHE/SME) methods.
Abstract: The extraction of wine aroma compounds was studied by direct-SPME (DI/SPME), headspace-SPME (HS/SPME) and multiple-headspace-extraction-SPME (MHE/SPME). The aromagrams obtained by HS/SPME-CGC were evaluated with chemometrical methods for the varietal classification of wines.