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Analytical procedure for the determination of toxicologically relevant arsenic (the sum of arsenite, arsenate, monomethylarsonate and dimethylarsinate) in urine by flow injection hydride generation and collection of generated inorganic and methylated hydrides on an integrated platform of a transverse-heated graphite atomizer for electrothermal atomic absorption spectrometric determination (ETAAS) is elaborated. Platforms are pre-treated with 2.7 micromol of zirconium and then with 0.10 micromol of iridium which serve both as an efficient hydride sequestration medium and permanent chemical modifier. Arsine, monomethylarsine and dimethylarsine are generated from diluted urine samples (10-25-fold) in the presence of 50 mmol L(-1) hydrochloric acid and 70 mmol L(-1)l-cysteine. Collection, pyrolysis and atomization temperatures are 450, 500, 2100 and 2150 degrees C, respectively. The characteristic mass, characteristic concentration and limit of detection (3sigma) are 39 pg, 0.078 microg L(-1) and 0.038 microg L(-1) As, respectively. The limits of detection in urine are ca. 0.4 and 1 microg L(-1) with 10- and 25-fold dilutions. The sample throughput rate is 25 h(-1). Applications to several urine CRMs are given.

Tl(I) and Tl(III) are preconcentrated simultaneously from aqueous solutions by colloid precipitate flotation using two collectors: hydrated iron(III) oxide (Fe(2)O(3).xH(2)O) and iron(III) tetramethylenedithiocarbamate (Fe(TMDTC)(3)). After the coprecipitation step and the addition of foaming agents, Tl(I) and Tl(III) were separated from the water by a stream of air bubbles. Various factors affecting Tl(I) and Tl(III) recoveries during the separation from water, including the collector mass, the nature of the supporting electrolyte, pH, zeta potential of the collector particle surfaces, type of tenside, etc., were investigated. Within the optimal pH range (6-6.5), establishing by a recommended procedure, Tl(I) and Tl(III) were separated quantitatively (94.9-100.0%) with 30 mg Fe(III). Both Tl ions were simultaneously separated without any previous conversion of one type of Tl ion to the other. Total Tl determination was performed by electrothermal atomic absorption spectrometry by previous matrix modification of the concentrated samples. The determination limit of Tl by this method is 0.108 mug l(-1).