Comparative-study of ruthenium, rhodium and palladium as chemical modifiers in graphite-furnace atomic-absorption spectrometry

Comparative study on the efficiency of ruthenium, rhodium and palladium as chemical modifiers for thermal stabilization of 18 analyte elements with high and moderate volatility has been performed. Addition of ascorbic acid provided higher temperatures of thermal pretreatment by +50 to +250-degrees-C for the analytes: As, Ge, P, Pb, Se, Sn and Tl, as well as better performence for Ga, In and Tl. Possible mechanisms and trends in stabilization are discussed

Chemical modification in electrothermal atomic-absorption spectrometry - organization and classification of data by multivariate methods - invited lecture

The vast amount of published work on chemical modification in electrothermal atomic absorption spectrometry (about 700 papers) has been critically examined and reviewed. Until now the chemical modification technique has been applied to the determination of 47 analyte elements in various matrices, and a large variety of different chemical modifier combinations (more than 150) have been found in the literature. An attempt has been made to organize and classify this large amount of empirical information. Various theoretical and experimental approaches have been used, such as the guiding and prediction power of the Periodic Table; the concept of isomorphism between analyte-analyte, analyte-modifier and modifier-modifier pairs; multivariate methods based on several sets of fundamental parameters and experimental data for the analyte or modifier elements: cluster, correlation, discriminant and factor analysis; thermodynamic calculations; data for the electronic configuration of analyte elements of their ions; and experimental data on maximum thermal pre-treatment temperatures in the presence of series of chemical modifiers. By using these various techniques, classifications for chemical modifiers and analyte elements have been proposed and discussed

Chemical modification in electrothermal atomic absorption spectrometry

Advances in chem. modification electrothermal at. absorption spectrometry (ETAAS) are reviewed with an emphasis on the progress made after the publication of the previous extensive review (Tsalev et al., Spectrochim. Acta Rev. 1990, 13, 225). Among the topics discussed are the useful effects, drawbacks, and limitations of chem. modifiers; thermal stabilization and isoformation effects; the rational integrating of chem. modification in anal. procedures; classifications of modifiers and analytes based on theor. and empirical approaches; mechanisms; guidelines for selection and optimization of chem. modifier compns.; and the progress made on mixed, composite, and permanent modifiers. The review is supplemented by an exhaustive bibliog. of .apprx.1000 refs. covering the period of 1990-1996. This large amt. of information is organized in four tables arranged in an alphabetical order of analyte elements for easy ref.: non-ETAAS applications of chem. modification in electrothermal vaporization-plasma spectrometric techniques; applications of instrumental techniques; and theor. approaches for studying mechanisms, recent anal. procedures involving chem. modification, and applications in preconcn. and speciation studies. [on SciFinder (R)

Kinetic approach to the interpretation of analyte losses during the preatomization thermal-treatment in electrothermal atomization atomic-absorption spectrometry

A method for evaluating E(a) (loss), the apparent activation energy of the analyte loss process during the high-temperature thermal pretreatment stage in electro-thermal atomization atomic absorption spectrometry (ETA-AAS) has been developed. The method is based on extracting information from the declining portion of thermal pretreatment curves (in this case presented as absorbance vs pyrolysis time at various fixed temperatures). Five volatile analytes (As, Pb, Sb, Se, and Sn) have been studied in the presence of tungsten chemical modifier (20-mu-g of W in H2O2). The data on E(a) (loss) have been utilized together with those obtained from treating the atomization peaks E(a) and with literature data on known values of bond energies and enthalpies of certain chemical reactions. Possible mechanisms of analyte losses and atomization are discussed

Simplified kinetic-model describing the analyte losses during pre-atomization thermal-treatment in electrothermal atomic-absorption spectrometry

A proposed kinetic model for elucidating the analyte pre-atomization losses in electrothermal atomic absorption spectrometry has been extended and developed further. The apparent activation energies, E(a)(loss), characterizing the process of analyte losses, have been derived from experimental data on absorbance and pre-treatment times at various pre-treatment temperatures for Sb, As, Pb and Sn, both in the absence and presence of a chemical modifier (20-mu-g of Mo(VI)). In the presence of a modifier, the maximum thermal treatment temperatures and the E(a)(loss) values were substantially increased and were of the same order, about 1300 K and 350 kJ mol-1, respectively, for the analytes As, Sb and Sn. For Pb, the corresponding values were 973 K and 60 kJ mol-1

Direct electrothermal atomic absorption spectrometric determination of lead in wine

A method for direct electrothermal at. absorption spectrometric detn. of lead in wine is described. A mixed chem. modifier contg. 20 mg of tungsten as ammonium paratungstate and 4 mg palladium as palladium chloride is applied to thermally stabilize Pb in wine up to pyrolysis temps. of 800-850 DegC. Matrix-matched stds. are used for calibration. The characteristic mass for integrated absorbance measurements (mo) is 20 pg, and the limit of detection is 3 mg/L for a wine sample. The accuracy and precision of the method were assessed by analyzing the ref. CQiR and CQiB materials (Food Science Lab., Ministry of Agriculture, Fisheries and Food, UK

Direct electrothermal atomic absorption spectrometric determination of lead in wine

A method for direct electrothermal at. absorption spectrometric detn. of lead in wine is described. A mixed chem. modifier contg. 20 mg of tungsten as ammonium paratungstate and 4 mg palladium as palladium chloride is applied to thermally stabilize Pb in wine up to pyrolysis temps. of 800-850 DegC. Matrix-matched stds. are used for calibration. The characteristic mass for integrated absorbance measurements (mo) is 20 pg, and the limit of detection is 3 mg/L for a wine sample. The accuracy and precision of the method were assessed by analyzing the ref. CQiR and CQiB materials (Food Science Lab., Ministry of Agriculture, Fisheries and Food, UK)