Stephen G. Capar

Critical evaluation of a multi-element scheme using plasma emission and hydride evolution atomic-absorption spectrometry for the analysis of plant and animal tissues

An analytical scheme that uses inductively coupled argon plasma emission spectroscopy (ICAP) and hydride evolution atomic-absorption spectrometry (HEAA) for the determination of trace elements in plant and animal tissues has been evaluated. The scheme incorporates the ion-exchange procedure of Kingston et al., which uses Chelex 100 resin to concentrate trace elements and remove potentially interfering alkali and alkaline earth metals. The separation procedure is included in a scheme designed to maximise the number of analyte metals that can be determined from a single digestion of a biological matrix. Acid-digested samples are divided into two fractions. One fraction (5% of the total) is measured directly by ICAP for alkali and alkaline earth metals and phosphorus and for transition metals such as iron and manganese, which are not well behaved on the resin. The other fraction (95% of the total) is subjected to the separation procedure whereby a number of biologically important trace elements, including cadmium, copper, molybdenum, nickel, vanadium and zinc, are initially sequestered by the resin, and then stripped into a small volume of dilute nitric acid for ICAP measurement of the “matrix-free” analytes. Arsenic, selenium and antimony, which are not retained by the resin, are collected with the initial column effluent, acidified and determined by HEAA. The reliability of the scheme is influenced by the nature of the acid digestion procedure used to oxidise the organic matrix. The scheme was tested by analysis of ten National Bureau of Standards biological reference materials.

Atomic emission spectrometric detection limits and noise power spectra of argon inductively coupled plasma discharges formed with laminar- and tangential-flow torches

Atomic emission spectrometric detection limits and noise power spectra were measured for argon inductively coupled plasmas (Ar ICPs) formed in tangential- and laminar-flow torches. To identify the origin of the noise sources from the sample introduction systems and the plasmas, noise power spectra were collected for two frequency ranges: 0–35, and 0–1060 Hz. In contrast to previous reports, the replacement of tangential flow by laminar flow resulted in no significant improvement in the detection power of the Ar ICP when torches with extended outer tubes were used.

Continuous Hydride Generation-Atomic Absorption Method for the Determination of Selenium and Arsenic in Foods

Abstract Determination of selenium and arsenic by continuous hydride generation-atomic absorption spectrometry is described. The method eliminated the use of a carrier gas for transport of hydrides to the atomizer. Detection limits for selenium and arsenic in foods were 5 and 3 ng/g, respectively. Calibration curves were linear from 2 to 600 ng/mL. The method can be applied to analysis of foods and standard reference materials.

Fortification variability in rat diets fortified with arsenic, cadmium, and lead.

Eleven rat diets fortified with 200 ppm Pb as lead acetate, and/or 50 ppm Cd as cadmium chloride, and/or 50 ppm As as sodium arsenate or p-arsanilic acid for use in a feeding study to determine the interactive effects of the three elements in rats were analyzed to confirm the fortification levels. Gross inhomogeneity was found. After remixing, variability within and among diets was improved but was still unacceptable. Fortification levels of Pb and of As as sodium arsenate could be accurately determined only by taking a very large sample and homogenizing the diet subsamples with a Polytron homogenizer. A review of the recent literature indicates that no standard procedures exist for fortification, mixing, or analysis of animal feeding study diets. Such procedures should be developed and analysis of the diets before and at intervals during a feeding study should be adopted as standard procedure.