Underestimation of the total arsenic concentration by hydride generation techniques as a consequence of the incomplete mineralization of arsenobetaine in acid digestion procedures

Individual arsenobetaine (AsB) decomposition products obtained with five di fferent acid digestion procedures (nitric acid/200 degreesC/10 or 30 min, n itric acid/sulphuric acid/300 degreesC/10 or 30 min and nitric acid/sulphur ic acid/hydrogen peroxide/300 degreesC/30 min) were determined by high-perf ormance liquid chromatography-(ultraviolet digestion)-hydride generation at omic fluorescence spectrometry (HPLC-(UV)-HGAFS). It was found that AsB was converted to mainly inorganic arsenic, trimethylarsine oxide (TMAO) and di methylarsinic acid (DMAA), depending on acid digestion procedure; the "stro nger" the digestion procedure the more mineralization occurred. The sensiti vity of the flow injection-hydride generation atomic fluorescence spectrome try (FI-HGAFS) for each of the decomposition products was also measured whi ch allowed us to calculate the FI-HGAFS response, and thus the total arseni c concentration using arsenate as a quantification standard. Total arsenic concentrations calculated were between 56 and 100% of the initially present AsB, depending on acid digestion procedure. This was completely in accorda nce with total arsenic concentrations measured so that underestimation of t he total arsenic concentration in AsB digests measured by the FI-HGAFS can be fully explained in terms of incomplete mineralization and the lower resp onse of the partly degraded products. (C) 2001 Elsevier Science B.V. All ri ghts reserved.