Arsenic, cadmium and lead in medicinal herbs and their fractionation.

Arsenic, cadmium and lead were determined for quality control monitoring purposes of Bulgarian herbs and their infusions by inductively coupled plasma mass spectrometry and electrothermal atomic absorption spectrometry. Twelve samples of yarrow (Achillea millefolium), 18 of chamomile (Flores Chamomillae), 8 of bearberry leaves (Folia uvae ursi), 24 of peppermint (Mentha piperitae folium), 10 of hibiscus (Hibiscus sabdariffa), 14 of oregano (Origanum vulgare) and 12 of thyme (Thymus serpyllum) were analyzed. The studied toxic elements were present in the medicinal plants (12-225 microg/kg As, 15-268 microg/kg Cd, 0.2-8.6 mg/kg Pb). Arsenic was found in all herbal infusions at levels up to 0.4 microg/l. Cadmium was present in infusions of chamomile, hibiscus, peppermint and thyme at levels up to 0.7 microg/l. Lead was detected only in hibiscus infusions (2-3 microg/l). It was established that the major part of arsenic and lead in herbal infusions existed in biomacromolecular fraction. Cadmium appears to be present mainly in cationic form at pH 1 (stomach acidity), but at pH 7.6 (intestine acidity) there is a non-cationic fraction as well.

Determination of trace metals in high purity gold.

The possibility of using ETAAS or ICP-AES for the determination of trace amounts of Ag, Bi, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Pd, Pt and Sb in pure gold is investigated. The influence of the matrix element on the atomization of the trace analytes is studied and optimal instrumental parameters are defined. An analytical method based on matrix element reductive separation followed by spectrometric determination of trace analytes is proposed as an alternative for the analysis of high purity gold. Advantages and disadvantages of proposed analytical procedures from the viewpoint of achieved repeatability, reproducibility and detection limits and of the duration of analysis are discussed.

Electrothermal atomic absorption spectrometric determination of trace elements in high-purity silver after total and partial reductive separation of the matrix.

A sensitive and reliable ETAAS determination of metal traces in high purity silver after total (Bi, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb) and partial (As, Hg, Sb, Se) separation of the matrix with ascorbic acid is described. The temperature program is optimized for analyte determination in ascorbic acid media and in 1% silver solution.

Behaviour of the dithiocarbamate complexes of arsenic, antimony, bismuth, mercury, lead, tin and selenium in methanol with a hydride generator.

A study was carried out with a continuous hydride generator coupled to an atomic emission spectrometer with inductively-coupled plasma to determine whether hydrides of As, Bi, Pb, Sb, Sn and Se and mercury vapor could be generated in methanol solutions of their dithiocarbamate complexes. It was found that (with the exception of Pb) hydride generation with sufficient efficiency for simultaneous multi-element determination is achieved using 0.25% NaBH(4)-0.6 mol 1(-1) HCl as reaction medium. The detection limit was found to be 0.2 ng ml(-1) for As, 30 ng ml(-1) for Bi, 0.03 ng ml(-1) for Se, Sb and Sn.

Liquid-liquid extraction of metal ions by the 6-membered N-containing macrocycle hexacyclen.

The nitrogen-containing analogue of 18-crown-6, 1,4,7,10,13,16-hexa-azaoctadecane (hexacyclen)] was studied as a reagent for complexation and extraction of some metal ions. It was found that with this reagent and methyl isobutyl ketone, metal ions such as silver(I), mercury(II), copper(II), platinum(II) and palladium(II) can be quantitatively extracted and separated from iron(III) and some other metal ions.