On-line UV-photooxidation with peroxodisulfate for automated flow injection and for high-performance liquid chromatography coupled to hydride generation atomic absorption spectrometry

An automated on-line UV photooxidation with peroxodisulfate of some environmentally relevant organoarsenic and organotin compounds in a system built from commercially available modules has been studied and optimised with a view to both species-independent quantification of the total arsenic or tin in samples containing different organic species by flow injection hydride generation atomic absorption spectrometry (FI-HGAAS) and speciation analysis by coupled high-performance liquid chromatography (HPLC) with HGAAS detection. For organoarsenicals, the reaction with alkaline peroxodisulfate in a 10-15-m knotted reactor for > 1.5 min insures > 90% transformation of inorganic As(III) and six organoarsenic species to arsenate: monomethylarsonate, dimethylarsinate, arsenobetaine, arsenocholine, trimethylarsine oxide and tetramethylarsonium. For organotins, the UV photooxidation with acidic peroxodisulfate at 95-100 degrees C provides recoveries of > 80% for the inorganic tin, dimethyltin, trimethyltin, triethyltin, tripropyltin, triphenyltin, monobutyltin, dibutyltin and tributyltin but only approximately 15% for tetrabutyltin. The best characteristic masses in integrated absorbance (A(int)) and peak-height (A(p)) measurements, respectively, are 30 pg and 480 pg for arsenic(V) and 22 pg and 410 pg for tin(IV), employing 100-mu l injections. The RSDs are 5.5% and 8.5% at 5 ng As(V) levels and 4.3% and 6.4% at 10 ng Sn(IV) levels in A(int) and A(p) modes, respectively. The limits of detection (LOD, 3 sigma) for As are 7 mu g l(-1) and 4 mu g l(-1) in FI-UV-HGAAS and HPLC-UV-HGAAS, respectively. The LODs for i-Sn(IV) are 2 mu g l(-1) in FI-UV-HGAAS, with both A(int) and A(p) measurements. The sample throughput rates are 20 and 12 samples per hour with 10-m and 15-m knotted reactors (i.d. 0.5 mm), respectively. Urine certified reference materials containing 0.052-0.48 mu g ml(-1) As have been analysed for their total arsenic content. (C) 2000 Elsevier Science B.V. All rights reserved.