Walter Kosmus

Speciation of selenium compounds with ion-pair reversed-phase liquid chromatography using inductively coupled plasma mass spectrometry as element-specific detection

For selenium speciation analysis, the hyphenation of chromatographic separation with element-specific detection has proved a useful technique. A powerful separation system, which is capable of resolving several biologically and environmentally important selenium compounds in a single column, is greatly needed. However, that has been difficult to achieve. In this paper eight selenium compounds, namely, selenite [Se(IV)], selenate [Se(VI)], selenocystine (SeCys), selenourea (SeUr), selenomethionine (SeMet), selenoethionine (SeEt), selenocystamine (SeCM) and trimethylselenonium ion (TMSe+), were separated by using mixed ion-pair reagents containing 2.5 mM sodium 1-butanesulfonate and 8 mM tetramethylammonium hydroxide as a mobile phase. The separation of these anionic, cationic and neutral organic selenium compounds on a LiChrosorb RP18 reversed-phase column took only 18 min at a flow-rate of 1.0 ml/min with isocratic elution, and baseline separation among the six organic Se compounds was achieved. Inductively coupled plasma mass spectrometry (ICP-MS) was employed as element-specific detection. A comparison of ICP-MS signal intensity obtained with a Barbington-type nebulizer and with an ultrasonic nebulizer (USN) was made. Different signal enhancement factors were observed for the various selenium compounds when a USN was used. The speciation technique was successfully applied to the study on chemical forms of selenium in a selenium nutritional supplement. Selenomethionine was found to be the predominant constituent of selenium in the supplement.

Essential trace elements in humans. Serum arsenic concentrations in hemodialysis patients in comparison to healthy controls.

Serum arsenic concentrations of persons suffering from renal failure and undergoing hemodialysis treatment (n=85) and of healthy controls (n=25) were determined by hydride-generation AAS technique after microwave digestion. The results were evaluated by comparing the values of both groups, considering physiological factors and individual data, as well as comorbid conditions of the hemodialysis (HD) patients. Serum arsenic levels were diminished in the patient group compared with controls (mean values 8.5±1.8 ng/mL vs 10.6±1.3 ng/mL). Furthermore, additional diseases within the hemodialysis group, particularly injuries of the central nervous system (CNS), vascular diseases, and cancer, were correlated to occasionally markedly decreased serum arsenic concentrations. It was concluded that arsenic homeostasis is disturbed by HD treatment and certain additional diseases. Desirable arsenic concentrations in the body seem to be reasonable. This consideration results in the conclusion that arsenic could play an essential role in human health. Thus, reference arsenic concentrations in different human tissues and body fluids should be established in order to recognize not only arsenic intoxication, but also arsenic deficiency. Perhaps arsenic deficiency contributes to the increased death risk of HD patients, and therefore, arsenic supplementations for patients with extremely low serum arsenic concentrations should be taken into account.

Modified electrical heating system for hydride generation atomic absorption spectrometry and elaboration of a digestion method for the determination of arsenic and selenium in biological materials

Abstract A modified electrical heating system for hydride generation atomic absorption spectrometry has been designed. The heating block permits a rapid and convenient change of the quartz tube in order to clean and condition its surface. Frequent conditioning guarantees high and constant measurement sensitivity. Further, an inexpensive and simple microwave digestion procedure has been developed. The methods were tested by analysing reference materials and proved to be appropriate for trace concentrations of arsenic and selenium.

Speciation of arsenic compounds by coupling high-performance liquid chromatography with inductively coupled plasma mass spectrometry

There is considerable evidence that toxicity and physiological behavior of arsenic depends on its chemical forms. Arsenic speciation became therefore the subject of increasing interest in recent years. A sensitive method for the determination of arsenic species has been developed. The proposed procedure involves the use of high-performance liquid chromatography and inductively coupled plasma mass spectrometry (HPLC-ICP-MS). Six arsenic compounds were separated by anion-exchange chromatography with isocratic elution using tartaric acid as mobile phase with an elution order: arsenocholine, arsenobetaine, dimethylarsinic acid, methylarsonic acid, arsenous acid and arsenic acid. The chromatographic parameters affecting the separation of the arsenic species were optimized. Analytical characterization of the method has been realized with standard solutions. The detection limits for six arsenic compounds were from 0.04 to 0.6 μg/L as As element. The repeatability (expressed by R.S.D) was better than 7% for all investigated compounds. The HPLC-ICP-MS system was successfully applied to the determination of arsenic compounds in environmental and biological samples in μg/L level.

Mo scf calculations on isocyanates

Abstract Calculations on some isocyanates have been performed by means of semi-empirical MO methods (CNDO/2). The NCO group is found to be nonlinear, in agreement with recent experimental result. Energies, charge densities and bond indices are discussed in relation to the stability of these compounds.

Simultaneous Speciation of Arsenic and Selenium Compounds by ION-Chromatography with Inductively Coupled Plasma Mass Spectrometry as Elemental Specific Detector

Abstract The feasibility of simultaneous speciation of arsenic and selenium compounds after ion chromatographic separation was investigated using inductively coupled plasma mass spectrometry (ICP-MS) as multielement specific detector. Separation conditions were optimized. Under the optimized conditions, six arsenic species: arsenous acid [As (III)], methylarsonic acid (MA), dimethylarsinic acid (DMA), arsenic acid [As(V)], arsenobetaine (AsB), arsenocholine (AsC), and four selenium species: selenous acid [Se(IV)], trimethylselenonium cation (TMSe+), selenocystine (SeCys), selenomethionine (SeMet), can be separated in the same injection within 8 minutes and determined at environmental concentration levels. The detection limits are estimated in the range of 0.04–0.6 μg/L for arsenic compounds and 0.18–0.35 μg/L for selenium compounds.

The chromatographic behavior of arsenic compounds on anion exchange columns with binary organic acids as mobile phases

SummaryIdentification and quantification of arsenic compunds was performed with high- performance liquid chromatography (HPLC) and flame atomic absorption spectrometry (FAAS) as element-specific detector. Arsenous acid, methylarsonic acid, dimethylarsinic acid, arsenic acid, arsenobetaine, and arsenocholine were separated on two anion-exchange columns (Synchropak Q 300 and PRP-X 100) with different binary organic acids as mobile phases. The infleunce of chromatographic parameters, such as pH and the concentration of the mobile phase were investigated. An unusual chromatographic behavior of arsenous acid was observed when tartaric acid was used as mobile phase.

Beiträge zur Chemie der Kohlensäurederivate, 3. Mitt.: Neue Synthesen von Tris(trimethylsilyl) cyanurat,N-Chlorsulfinylimid und Chlorcyan

Tris(trimethylsilyl)cyanurate (I) has been prepared in high yields by silylation of cyanuric acid with trimethylsilyl cyanide, as well as by the reaction of trichloroisocyanuric acid with trimethylsilyl cyanide or trimethylsilylsulfinylimide. The latter reactions, yielding Cl−CN and Cl−NSO resp. as the only by-products, are convenient methods for synthesizing these pseudohalogen-chloride compounds in a very pure state. Starting fromN-chlorocarbonyl isocyanateI is formed in high yields by a complex reaction with trimethylsilylsulfinylimide too. Based on IR, Raman and1H-NMR data the O-silyl structure ofI was confirmed. The formation of products with N-silyl or N,O-silyl structure was never observed.

Influence of humic and low molecular weight polycarboxylic acids on the release of arsenic from soils

The effect of humic acid and some low molecular weight polycarboxylic acids (LMWPAs) (phthalic, oxalic, and citric) on the release of arsenic has been studied by adding various amounts of the acids to a soil collected from a grazing land in south eastern part of Austria (Gasen). All the organic acids studied were found to enhance the release of arsenic, but not to the same extent. The trend in the release observed with HA treatment varied remarkably from the LMWPA treatments. The LMWPAs were more effective in releasing arsenic as compared to humic acid at pH 2, 3, 5, 7 and 8. Concentration of released arsenic increased substantially as the quantity of added acid increased, while it decreased with an increase in pH. With humic acid, unlike in the case of the LMWPA the release of arsenic increased with an increase in pH. The simultaneous release of Fe and Al has also been studied and results obtained showed that the release of As is strongly related to the formation of soluble complexes between the acids investigated and these elements.

Multi-element determination in earthworms with instrumental neutron activation analysis and inductively coupled plasma mass spectrometry: A comparison

Earthworms were collected from agricultural fields in Admont, Graz, Piber and Gumpenstein, Austria. Six earthworm samples were investigated with INAA and with ICP-MS in parallel for the element concentrations of As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Pb, Rb, Sb, Se and Zn. With both techniques 14 elements were analysed in a wide concentration range (ng/g to mg/g) GF-AAS and HG-AAS were used for verification of some element concentrations. A comparison of analytical results between INAA and ICP-MS was discussed. In general, good agreement between ICP-MS and INAA was obtained, the relative difference values of most of the elements are within ±20% range, however, a methodical error for the determination of Hg by ICP-MS was found.