Determination of minor element concentrations in reference materials

It has been shown, for a Pb isotopic reference material and for natural Cd, that total evaporation with integrating mass spectrometric measurement allows the determination of isotope ratios of these elements with sufficient accuracy and reproducibility. It is possible to use the method in carefully selected cases for IDA-TIMS measurements without the application of bias factors derived from isotopic reference material measurements. IDA-TIMS measurements were used for the determination of Cd (40–400 g/g) in polyethylene and Cd (10 g/g), Pb (500 g/g), Ga (150 g/g) and Zn (2000 g/g) in the Al alloy AlCuMg2. Relative standard deviations (n=5) were between 1.2% to 2.4% in the first case and 0.3% for Cd, 0.4% for Ga, 0.14% for Pb, 0.6% for Zn in the second. Deviations from the certified values were between 0.8% and 1.4% in the first case. The four concentration values contributed to the AlCuMg2 certification measurements but deviated from the finally certified values as follows: Cd+1.0%, Ga–1.6%, Pb–0.9% and Zn+10%.     

Determination of cadmium in tobacco smoke and zinc in tap water by solvent extraction flame atomic absorption spectrometry

Procedures are described for the determination of cadmium in tobacco smoke and zinc in tap water by flame atomic absorption spectrometry after chelation with benzyl 2-pyridyl ketone 2-pyridylhydrazone and extraction with isobutyl methyl ketone. Calibration graphs in the organic layer were linear up to 1.3 g/ml, with sensitivities of 80 ng/ml (Zn) and 71ng/ml (Cd), and limits of detection of 49 ng/ml for zinc and 38 ng/ml for cadmium. RSD values were 2.9% at 0.42 g/ml (Cd) and 4.7% at 0.17 g/ml (Zn).     

Verfahren zur Trennung und Anreicherung bei der Atomabsorptionsspektrometrie von Spurenverunreinigungen in schwerl?slichen Bleiverbindungen

Zusammenfassung Ein Trenn- und Anreicherungsverfahren zur AAS-Spurenanalyse in PbCl₂ und PbSO₄ wird beschrieben. Die Analysenproben werden im festen Zustand in einen Pb(DDTC)₂-Niederschlag umgewandelt. Die dabei gebildeten Dithiocarbamatkomplexe von Fe, Cu, Co, Ni, Cd, Zn werden durch Dreiphasenextraktion in MIBK konzentriert und mittels Flammen-AAS analysiert. Die Methode erlaubt die Bestimmung von 0,3 g/g Fe, 0,2 g/g Co, Ni und 0,05 g/g Cu, Cd, Zn mit einer relativen Standardabweichung von 0,5 bis 5%.

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Method for the separation and concentration of trace elements in the atomic absorption spectrometric analysis of insoluble lead compounds

Summary A method for the separation and concentration of trace elements in the analysis of PbCl₂ and PbSO₄ is described. The solid samples are transformed to Pb (DDTC)₂. The DDTC-complexes of Fe, Cu, Co, Ni, Cd, Zn thus formed are concentrated using three-phase extraction with MIBK and determined by flame AAS. The detection limit amounts to 0.3 gmg/g Fe, 0.2 g/g Co, Ni and 0.05 g/g Cu, Cd, Zn with a relative standard deviation of 0.5–5%.

     

Continuous ultrasound-assisted extraction of cadmium from legumes and dried fruit samples coupled with on-line preconcentration-flame atomic absorption spectrometry

Cadmium was continuously extracted with diluted nitric acid from legumes and dried fruit samples using a simple, rapid and continuous ultrasound-assisted extraction system. A minicolumn packed with a chelating resin (Chelite P, with aminomethylphosphoric acid groups) was placed between the extraction unit and the detector for cadmium preconcentration. The cadmium content in the acid extract was retained into the minicolumn, and elution was carried out with hydrochloric acid, with this trace metal continuously monitored by flame atomic absorption spectrometry. An experimental design (Plackett-Burman 2⁶×3/16) was used to optimize the continuous leaching procedure and the preconcentration step. The method allowed a total sampling frequency of 10 and 14 samples per hour for legumes and dried fruit, respectively. The procedure displayed good precision (2.0 and 2.5%, respectively, expressed as relative standard deviations) for samples containing 0.202±0.005 g g^–1 Cd (broad bean) and 0.239±0.004 g g^–1 Cd (peanut). Detection limits of 0.014 g g^–1 Cd for 60 mg of legume samples and 0.011 g g^–1 Cd for 80 mg of dried fruit samples were obtained. The method was successfully applied to the determination of trace amounts of cadmium in legumes and dried fruit samples.     

Flame atomic absorption spectrometric determination of cadmium and copper in biological reference materials using on-line sorbent extraction preconcentration

Summary Cadmium and copper at the g/g to ng/g level in plant and animal tissue reference materials, and at the g/l level in urine were determined by flame atomic absorption spectrometry using on-line sorbent extraction preconcentration based on flow injection techniques. Bonded silica reversed phase sorbent with octadecyl functional groups (RP-C 18), packed in a 100 l column, was used to collect the diethylammonium-N,N-diethyldithiocarbamate (DDTC) complex formed on-line in the sample digests at low pH. Methanol was used to elute the analyte chelates directly into the nebulizer-burner system of the spectrometer. Small air segments introduced before and after elution prevented the eluent from mixing with the sample solution and increased the sensitivity. A sampling frequency of 85/h could be obtained with a sample loading time of 30 s at a flow rate of 4.0 ml/min. The enrichment factor for both elements was 20 and the enhancement factors, including the effect of the organic solvent and with the flow spoiler removed, were 126 and 114 for cadmium and copper, respectively. The detection limits (3) were 0.15 g/l for cadmium and 0.2 g/l for copper. The precision was 2.3% and 1.4% r.s.d. for 10 g/l Cd and 45 g/l Cu, respectively (n=11). Results for the determination of cadmium and copper in various biological reference materials were typically in good agreement with certified values. Low recoveries were observed, however, for cadmium in samples containing high levels of copper and/or iron, such as bovine liver.On leave from Flow Injection Analysis Research Center, Institute of Applied Ecology, Academia Sinica, Shenyang, China     

Characterization of a total diet reference material (ARC/CL HDP) for contents of essential and toxic elements

Summary A total diet reference material (RM) was prepared by employing material leftover from a nationwide Finnish hospital diet study. The material was carefully homogenized using Ti-blades, freeze-dried, rehomogenized with Ti-blades, passed through a 2 mm nylon sieve and carefully mixed in large glass cylinders. Homogeneity of the material divided into 20 g samples in polyethylene bottles was tested by taking ten 0.5 g samples from the beginning and end of the bottling line and analyzing them for Zn and Mg. The homogeneity was within 1.0% for both Zn and Mg. An interlaboratory comparison study involving reliable reference laboratories that employed a total of seven methods based on independent analytical principles was conducted on the contents of 14 mineral elements. After the exclusion of outliers the recommended concentrations (on a dry weight basis) expressed as the medians±95% confidence limits were established as follows: Ca=2.86±0.124 mg/g, Mg=785±25 g/g, K=9.42±0.30 mg/g, Na=7.87±0.57 mg/g, Fe=30.4±0.9 g/g, Mn=12.9±0.58 g/g, Zn=28.9±1.3 g/g, Cu=3.18±0.19 g/g, Mo=262±35 ng/g, Ni=271±38 ng/g, Se=181±17 ng/g, Pb=43±8 ng/g, Cd=21±3 ng/g and Hg=6.6±3.6 ng/g. All of the above recommended concentration ranges, except that for Ni, fell into category A, i.e. values recommended with a high degree of confidence according to the certification criteria established by Pszonicki.     

Bestimmung von Spurenelementen in Flu?wasser mit Hilfe der Voltammetrie

Zusammenfassung Bei der Bestimmung von Spurenelementen in Flußwasser durch Voltammetrie treten Störungen auf, die überwiegend von organischen Verunreinigungen verursacht werden. Die Einflüsse dieser Verunreinigungen können durch oxidative UV-Photolyse beseitigt werden.Im Anschluß an die Bestrahlung der Proben konnten in filtriertem Rheinwasser Zn, Cd, Pb, Cu, Ni, Co, Tl und mit Einschränkungen auch Mn voltammetrisch bestimmt werden. Die Konzentrationen an Bi und Se lagen unterhalb der Nachweisgrenze. Die Nachweisgrenzen für die genannten Elemente in Flußwasser bewegten sich in der Größenordnung zwischen 0,1 und 1 g/l. Vergleichsbestimmungen mit Hilfe der flammenlosen AAS (Graphitrohrküvette) ergaben gute Übereinstimmung für die Elemente Cu, Zn und Mn, während die Konzentrationen der anderen Elemente unterhalb der Nachweisgrenze der AAS lagen.Die Komplexierungskapazität des Rheinwassers für Zn, Cd, Pb und Cu wurde durch voltammetrische Titration ermittelt. Sie lag zwischen 5,0 und 0,7 g/l und nahm in der Reihenfolge Cu > Zn > Pb > Cd ab.

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Determination of trace elements in river water by means of voltammetry

Summary The determination of trace elements in river water by voltammetry is disturbed by the presence of organic substances. The influence of these substances can be eliminated by oxidative UV-photolysis.After UV irradiation the following elements were determined in Rhine water by voltammetry: Zn, Cd, Pb, Cu, Ni, Co, Tl and — with reservations — Mn. The concentrations of Bi and Se were below the detection limits. The detection limits in river water for the elements mentioned were determined and found to be between 0.1 and 1 g/l. Comparative determinations by AAS (graphite tube) showed good agreement for Cu, Zn and Mn, whereas the concentrations of the other elements were below the detection limits of AAS.The complexing capacity of Rhine water for Zn, Cd, Pb and Cu was determined by voltammetric titration. It decreased in the order Cu > Zn > Pb > Cd and was between 5.0 and 0.7 g/l.

     

Sample introduction assisted by compressed air in flame furnace AAS: a simple and sensitive method for the determination of traces of toxic elements

The power of detection of flame AAS for the toxic elements Cd, Hg, Pb and Tl can be improved by 1–2 orders of magnitude by using flame furnace AAS. In flame-furnace AAS, liquid samples are introduced directly into a nickel tube located in the flame, in the simplest case through a ceramic thermospray capillary. Transportation of the samples is achieved by using compressed air only. Comparatively low detection limits are achieved by both beam injection flame furnace (BIFF-AAS) and thermospray flame furnace AAS (TS-FF-AAS). For TS-FF-AAS, a pressure of less than 20 kPa (<80 in. water) is required. The TS-FF-AAS technique is very simple, robust and cheap. The detection limits were 0.2–0.4 g L^–1 (Cd), 40–100 g L^–1 (Hg), 5–9 g L^–1 (Pb) and 4–14 g L^–1 (Tl), respectively, depending on the method, flow rate and sample volume used. Pb and Cd were found at concentrations of 0.1–2 and 0.005–0.3 g g^–1, respectively, in samples of various spices.Dedicated to the memory of Wilhelm Fresenius.