Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Analytical and Bioanalytical Chemistry (v.358, #7-8)
Limits of tolerance and z-scores in ring tests by S. Uhlig; P. Henschel (pp. 761-766).
A series of objections are discussed to the use of symmetrical tolerance intervals in ring tests as part of a procedure for laboratory assessment. Instead, a modified, asymmetrical tolerance interval is introduced which takes these objections into consideration. A modified z-score is proposed corresponding to the modified tolerance interval.
Improved power of determination in SS-ZAAS using pellets of 10 to 20 mg for analysis by T.-M. Sonntag; M. Rossbach (pp. 767-770).
Solid sampling-Zeeman atomic absorption spectrometry (SS-ZAAS) has been a valuable tool for rapid, direct and reproducible element determination in a broad variety of biological, geological, and environmental materials for more than two decades. However, since the technique was applicable to small amounts of sample mass only (0.02–2.0 mg), until now quantitative analysis by SS-ZAAS has not gained adequate attention. With such a small quantity of sample analyzed, the requirements concerning the sensitivity of the technique or the homogeneity of the material to obtain meaningful results cannot always be fulfilled. Particularly for elements where only a relatively insensitive absorption line is available in relation to the content in low contaminated materials, the technique showed inadequate limits of analysis. In order to overcome these restrictions and to broaden the applicability of the technique, an attempt was made to introduce higher sample masses in the form of pressed pellets (5 to 20 mg) on the graphite boat of the sample introduction system. As an example the analytical parameters and results for thallium analysis in natural biological materials from the German Environmental Specimen Bank (ESB) and in Reference Materials are described. This approach widens the scope of SS-ZAAS as a sensitive, accurate, fast and direct analytical technique for biological and environmental materials and compares well with results obtained by more established techniques such as isotope dilution mass spectrometry with thermal ionization (ID-MS).
Determination of cobalt, copper, iron, nickel and zinc in cemented tungsten carbides with cobalt as a binder by FAAS: Matrix effect control by multivariate technique by T. Piippanen; Jouko Jaatinen; Aarni Pirjetä; Jouni Tummavuori (pp. 771-774).
A new approach for the determination of cobalt, copper, iron, nickel and zinc in cemented tungsten carbides with cobalt as a binder by flame atomic absorption spectrophotometry (FAAS) is reported. Real samples were dissolved in phosphoric, hydrochloric and nitric acid. PTFE bomb or alternatively small amounts of HF were used for the enhancement of the recovery of the elements investigated. Synthetic samples were used for interference studies. Multiple linear regression was applied for the control of matrix effects and it proved to be very effective in the search for interfering elements. Using simple acid based standards, all investigated elements could be determined sequentially in a complex matrix by using an appropriate method of calculation. The method described has been succesfully applied to real type commercial samples. Results were compared with those obtained by inductively coupled plasma atomic emission spectrometry (ICP-AES) and X-ray fluorescence spectrometry (XRF), being in good agreement with each other and having relative standard deviations better than 5%.
Application of factorial designs and simplex optimisation in the development of flow injection-hydride generation-graphite furnace atomic absorption spectrometry (FI-HG-GFAAS) procedures as demonstrated for the determination of trace levels of germanium by B. Hilligsøe; E. H. Hansen (pp. 775-780).
The optimisation of a volume-based FI-HG-GFAAS procedure is described for the trace determination of Ge, comprising in situ collection of the generated germane in the graphite furnace. The response function is the peak area readout (A × s). Based on a preliminary study, where factorial designs were used to identify significant factors and interactions, the procedure was optimised using both simplex and OVAT (one variable at a time) methods. The characteristics and merits of these methods are discussed. Under optimal experimental conditions, using a sample volume of 100 μL, Ge was determined at a sampling frequency of 22 h–1. The sensitivity, in terms of the characteristic mass, m0, was 26 pg/0.0044 A × s, with a detection limit of 0.21 μgL–1 (3σ). The precision (relative standard deviation) was 2.0% (n = 10) at the 1 μgL–1 level.
Multivariate data analysis of trace element content in animal organs measured by simultaneous atomic absorption spectrometry by U. Gottelt; G. Henrion; R. Henrion (pp. 781-784).
The simultaneous determination of trace elements in animal organs offers improved possibilities to characterize the geographical origin of the animal by analyzing its pollution characteristics. Pb, Cd, Ni (GF-AAS) and Cu, Zn, Fe, Mn (F-AAS) in kidneys and livers of cows from different sites have been measured using simultaneous AAS. The correct allocation of cows to specific regions shows that multivariate data analysis provides efficient tools for the geographical classification. The consideration of absorbance rather than concentration as the data input simplified the analytical procedures by omitting the calibration step.
Information theory and systematic toxicological analysis in “general unknown” poisoning cases by D. Thieme; R. K. Müller (pp. 785-792).
If qualitative analysis is aimed to detect large, imprecisely confined groups comprising hundreds or thousands of compounds – like during the analysis of questionable poisoning cases without direct hints, the so called “general unknowns”–, the evaluation of the identification certainty becomes equally important like the associated estimation of the necessary information capacity of the analytical procedures to be applied [1–4]. On this basis, the authors have outlined factors, which influence the usable information provided by analytical principles or procedures depending of the number and types (analytical categories, differences and similarities, detectability) of the analytes to be detected or included. A correlation between the usable information (excess or deficiency) and the probability of failing identifications is defined, and the information loss by interfering analytical signals is discussed. The concepts of discrimination power DP, identification power IP, and mean list length MLL [4–7] are associated with these considerations. Examples of analytical tasks in this “general unknown” environment of toxicological analysis are presented.
Gas analysis by infrared spectroscopy as a tool for electrical fault diagnostics in SF6 insulated equipment by H. M. Heise; R. Kurte; P. Fischer; D. Klockow; P. R. Janissek (pp. 793-799).
Infrared spectroscopy shows an enormous potential for the analysis of by-products generated from electrical discharges in sulfur-hexafluoride (SF6) insulated equipment. Since by-product composition can be related to the fault genesis (arc, partial discharge or corona), the analysis of contaminated SF6 provides a valuable diagnostic tool. The IR-spectrometric results from discharge experiments are presented, carried out with the application of SF6 pressures around 300 kPa and an alternating voltage up to 30 kV. Under the discharge conditions used, the main by-products found are the sulfuroxyfluorides SOF4 and SO2F2 with concentrations correlated to the discharge time. Due to its toxicity, special attention is also paid to S2F10. The experimental conditions and practical aspects for reliable quantitative analysis of reactive species are discussed.
Certification of 22 elements in a pure copper (99.5%) sample for spark emission and X-ray fluorescence spectrometry (CRM BAM-376) by K. A. Meier; S. Recknagel (pp. 800-803).
The element contents of Ag, Al, As, Be, Bi, Cd, Co, Cr, Fe, Mg, Mn, Ni, P, Pb, S, Sb, Se, Sn, Te, Ti, Zn and Zr in a pure copper (99.5%) sample (CRM BAM-376) for use in spark emission and X-ray fluorescence spectrometry were certified and the certified values are given. For Si, the certification has not yet been completed, the content of this element will be certified later. The sample was produced and certified in collaboration with the Committee of Chemists of the GDMB Gesellschaft für Bergbau, Metallurgie, Rohstoff- und Umwelttechnik. Data of the homogeneity testing and the certification campaign with 14 participating laboratories using different analytical methods are reported.
Sliding spark spectroscopy – rapid survey analysis of flame retardants and other additives in polymers by A. Golloch; Dirk Siegmund (pp. 804-811).
A sliding spark spectrometer with a new powerful excitation source was used to detect halogens, flame retardants and metals in non-chlorine containing polymers. The sliding spark source generated discharges using up to 2 kJ of stored energy. The new generator results in improved signal-to-background ratios (SBR) by the factor of three. With this source and a newly developed low cost charge-coupled device spectrometer it was possible to detect elements simultaneously in polymer materials within 5 s. Fillers and white pigments containing Pb, Ti, Zn, Si, Mg, Ca and Ba were qualitatively detected in polyethylene and polypropylene. Acrylnitrile-butadiene-styrene copolymer samples containing different types of flame retardants were analysed and Cl, Br, P, Sb, Al, Mg and Zn were detected. Limits of detection of about 0.1% w/w for elements in chlorine-free polymers were obtained. The use of multiple linear regression gave better results than the use of one individual spectral line.
Optimized pressure-pulse splitless injection and electron-capture, negative ionization detection for the congener specific determination of compounds of technical toxaphene by Richard Bartha; W. Vetter; Bernd Luckas (pp. 812-817).
The goal of the study is the optimization of the congener specific determination of compounds of technical toxaphene (CTTs). For this reason GC/ECNI-MS and CTT standard mixtures are applied. The splitless injection is improved by pressure-pulse injection which yields significantly higher abundance of the CTTs than by the conventional constant flow injection technique. The abundance of low volatile CTTs like B9-1025 (Parlar #62) is increased by factor 3 or more. The pressure-pulse injection can easily be integrated in standard (constant flow splitless injection) methods without influencing the retention times and reproducibility. The GC oven program and the flow are optimized for the separation of CTTs on a non-polar CP-Sil 2 column. Problems caused by oxygen in the ion source are discussed.
Determination of silver in fresh water by atomic absorption spectrometry following flotation preconcentration by iron(III) collectors by Katarina Čundeva; Trajče Stafilov (pp. 818-821).
Colloid precipitate flotation of silver from fresh water is applied for preconcentration and separation. Optimal conditions using hydrated iron(III) oxide and iron(III) tetramethylenedithiocarbamate as collectors were investigated. Various factors affecting the silver recovery, including collector mass, nature of the supporting electrolyte, pH of the working medium, electrokinetic potential of the collector particle surfaces, type of surfactant, induction time etc., were checked. Within the optimal pH range (5.5–6.5) silver was separated quantitatively (94.9– 100.0%) with 30 mg Fe(III) as collector. The content of silver was determined by electrothermal atomic absorption spectrometry and compared to that from inductively coupled plasma-atomic emission spectrometry. The detection limit of silver by the method described is 0.01 μg/L.
Supported liquid membrane enrichment using an organophosphorus extractant for analytical trace metal determinations in river waters by Nii-Kotey Djane; Kuria Ndung’u; Fredrik Malcus; Gillis Johansson; L. Mathiasson (pp. 822-827).
Metal ions were preconcentrated from water samples using supported liquid membranes containing 40% w/w di-2-ethylhexyl phosphoric acid (DEHPA) dissolved in kerosene as the membrane liquid. The driving force for the mass transport of analytes in this system is the pH gradient across the membrane. The effect of the carrier concentration on the extraction efficiency was studied. The mechanism for the mass transport in the system was investigated by measuring changes in pH and analyte ion concentration as well as changes in the concentration of other interfering metal ions present in large excess during the enrichment. The extraction efficiency was found to be unchanged as long as the pH difference across the membrane was more than 2 pH units. The long-term stability of the system was investigated at different pHs in the donor solution. Under optimal conditions, the membrane was stable for at least 200 h with reagent water samples and at least 80 h for river water samples. Enrichment factors of approximately 15 times could be obtained. The corresponding extraction efficiencies were over 80% for some of the investigated metal ions. The detection limits of blank samples for Cu2+, Cd2+ and Pb2+ using 120 min processing time were 0.19, 0.024 and 0.09 ng/mL, respectively.
Speciation analysis of organotin compounds in Thermaikos Gulf by GC-MIP-AED by S. Girousi; E. Rosenberg; A. Voulgaropoulos; M. Grasserbauer (pp. 828-832).
A rapid, sensitive and interference-free analytical procedure was applied to organotin speciation in sea water. The method was based on the ethylation of ionic organotin compounds in the aqueous phase with NaBEt4, followed by extraction of the derivatized species into hexane. The separation and determination of organotin species were performed by capillary Gas Chromatography-Microwave Induced Plasma-Atomic Emission Detection (GC-MIP-AED). The operational variables were ortimized for chromatographic resolution and detection limits. 100 mL of sample were used for the analysis and the detection limits, for butyltin species, were ranging from 17.7 to 33.4 ng/L (as Sn) and for phenyltin species, from 17.8 to 22.3 ng/L (as Sn). The method was applied to the determination of organotin species in samples collected from Thermaikos Gulf (Thessaloniki, Greece) at 4 sampling points and 3 sampling campaigns. The sampling points represented industrial, urban and harbour activities. In three samples collected during the second sampling campaign, and from three sampling points respectively, only dibutyltin species were present at concentration levels close to the detection limits.
Rapid determination of volatile organic compounds in environmentally hazardous wastewaters using solid phase microextraction by K. J. James; Mary A. Stack (pp. 833-837).
Solid phase micro-extraction (SPME) was applied to the determination of volatile organic compounds (VOC) in wastewater discharges. Environmentally significant samples, typical of those subject to regulatory control, were examined and included discharges from pharmaceutical, petrochemical and municipal sewerage treatment plants. Analysis was performed using gas chromatography – mass spectrometry (GC-MS) following sampling using headspace or immersion SPME. Fused silica fibres, coated with either poly(dimethylsiloxane) or poly(acrylate), were examined to determine VOC which included chloroform, saturated carboxylic acids, alkylbenzenes, phenol, benzonitrile and benzofuran. Detection limits varied from 10 to 170 ng/ml and satisfactory relative standard deviations (%RSD < 10) were obtained. For most samples, headspace sampling was preferred to immersion. SPME was found to be a useful technique for the rapid screening of wastewaters for VOC.
Determination of total arsenic in urine by hydride AAS after UV-digestion by R. Ritsema; E. van Heerde (pp. 838-843).
A method for analysing arsenic in urine samples by Flow Injection Analysis-Atomic Absorption Spectrometry (FIA-AAS) after ultra-violet (UV) digestion is developed and validated. The validated method has the following performance characteristics: limit of detection (LOD) 0.5 μg L–1, repeatability and reproducibility better than 5% and 10% relative standard deviation (RSD) respectively for arsenic concentrations above 3 μg L–1, linear range 0.5–40 μg L–1. Validation of the method was performed by analysing several certified reference materials. Results obtained were well within the certified intervals. Several urine samples analysed by UV-FIA-AAS were also analysed by Inductively Coupled Plasma-Mass Spectrometry after High Performance Liquid Chromatography (HPLC-ICP-MS) in order to investigate comparability. Again results were satisfactory, arsenic concentrations in urine samples did not differ from each other significantly. Storage conditions were also studied. Urine samples are best stored in polyethylene containers at 5 ± 4°C and are stable in arsenic content for at least 30 days.
Application of rapid electrothermal atomic absorption spectrometric methods to the determination of Ag, Al, Cd and Mn in cocaine and heroin samples by P. Bermejo-Barrera; Antonio Moreda-Piñeiro; Jorge Moreda-Piñeiro; Adela Bermejo-Barrera (pp. 844-847).
Rapid methods were developed for the direct determination of Ag, Al, Cd and Mn in cocaine and heroin by ETAAS using programmes omitting the charring step . Sample pretreatment was simple: dissolution in ultrapure water or in 35.0% (v/v) HNO3 for heroin or cocaine, respectively. Optimum drying temperatures were 250 °C for Ag, Al and Mn, and 300 °C for Cd. The run cycles were 35 and 37 s, for Ag and Al respectively, and 36 s for Cd and Mn. The best results were obtained with Pd, Mg(NO3)2 and (NH4)2HPO4, as chemical modifiers. The limits of detection were 8.6, 55.9, 2.2 and 12.4 μg kg-1 for Ag, Al, Cd and Mn, respectively.
Analysis of the distribution of lead, cadmium and mercury in the avian kidney by means of direct solid sampling electrothermal atomic absorption spectrometry by Ernst Lücker (pp. 848-853).
The distribution of Pb, Cd and Hg was studied in 3 sets of 10 pairs of avian kidneys by means of direct solid sampling electrothermal atomic absorption spectrometry (SS-ETAAS). The hierarchic model for the analysis of variance for each element consisted of 10 animals, 2 pairs of kidneys, 3 sampling sites and 6 microsamples (n=360). Heterogeneity was found to be only a minor source of analytical variance in Pb, Cd and Hg. The kidney of an animal as component of variance was of no significant influence. However, the variance of the sampling site was highly significant in the case of Pb and Cd. Here, total analytical variance must be reduced by means of an adequate sampling strategy. For six replicates with each microsample taken from a different sampling site, the variance of mean value estimation as represented by the total distribution factor is reduced from 1.20 to 1.08 and from 1.19 to 1.07 in the case of Pb and Cd, respectively. In Hg-determinations, the respective factor is reduced from 1.23 to 1.09 with the sampling strategy having nearly no effect. Results of direct SS-ETAAS determinations of Pb, Cd and Hg in non-homogenized avian kidneys are considered to be highly representative, even more than in previous studies of mammalian kidneys and livers, due to the larger part of material which is actually analyzed.
Comparison of NTIMS and ICP-OES methods for the determination of boron concentrations in natural fresh and saline waters by S. Barth (pp. 854-855).
Determination of B concentrations in natural fresh and saline waters by ICP-OES may be strongly affected by matrix effects resulting in a deviation (shift to apparently lower values) in the order of 10 to 20% (if working without matrix-matched standard solutions), at variance with the NTIMS (Negative Thermal Ionization Mass Spectrometry) isotope dilution technique which is virtually unaffected by such effects. NTIMS isotope dilution is a highly sensitive, precise and effective technique which requires only trace amounts of boron (1–10 ng B) and allows boron concentrations in natural waters to be analyzed with an analytical uncertainty of ± 2% (2 σ).
A novel preconcentration technique using crosslinked chitosan for the determination of mercury by CVAAS by Meilin Wang; Ganquan Huang; Shahua Qian; Jianshen Jiang; Yuting Wan; Y. K. Chau (pp. 856-858).
A novel crosslinked chitosan (CCTS) has been synthesized by the reaction of water-soluble chitosan with epoxy chloropropane. In the presence of the chelating EDTA and in the pH range between 4–10, CCTS selectively adsorbed trace inorganic Hg in water samples with enrichment factors of 100. Inorganic Hg could be directly reduced using KBH4 without preceding elution and determined by CVAAS. Accordingly, the total mercury could be determined after all species of mercury in water samples were transformed into Hg2+. The detection limit (3σ) for mercury was 12 ng L–1 and the relative standard deviation less than 5% at the 50 ng L–1 level. Beer’s law was obeyed over the range 30–400 ng L–1 of mercury and the preconcentration method was applied to environmental water samples with the recoveries between 92–96%.
Anodic stripping voltammetric determination of total lead, copper and selenium in whole blood and blood serum by H. Aydın; Özcan Oruç (pp. 859-860).
A two-step procedure including appropriate wet-digestions, separation of selenium from interfering ions such as heavy metal ions with pentyl alcohol and anodic stripping voltammetric (ASV) determination of Pb2+, Cu2+ and SeO3 2– is developed. The elements in digested whole blood and serum sample solutions were determined by using a standard addition method. 1 × 10–9 mol/L SeO2– 3, Cu2+ and Pb2+ were successfully determined with relative standard deviations of approximately 1–2% (n = 6–8).
Highly sensitive chemiluminescence flow sensor for ascorbic acid by W. Qin; Z. J. Zhang; H. H. Chen (pp. 861-863).
A highly sensitive chemiluminescence(CL) flow sensor is proposed for the determination of ascorbic acid. The analytical reagents luminol and iron(II) are immobilized on anion-exchange and cation-exchange resins, respectively, and can be eluted by sodium sulphate. The calibration graphs are linear in the range 1 × 10–9 to 1 × 10–6 g mL–1 and the detection limit is 4.0 × 10–10 g mL–1. The sensor has been applied successfully to the determination of ascorbic acid in vegetables.
Electrocatalytic oxidation of dopamine at the polyglycine chemically modified carbon fiber bundle electrode and its voltammetric resolution with uric acid by H.-Y. Chen; A.-M. Yu; Hai-Li Zhang (pp. 863-864).
A polyglycine chemically modified electrode shows substantial catalytic ability towards dopamine (DA). The calibration graph obtained by linear sweep voltammetry for DA is linear in the range 2.0 × 10–8∼ 4.4 × 10–6 mol/L and the detection limit is ca. 5.0 × 10–9 mol/L. The catalytic ability towards DA results in the voltammetric resolution of DA and uric acid (UA) in the same solution, which is impossible at the unmodified electrode. Uric acid in less than 120-fold excess does not interfere with the determination of DA.