SPECIATION BY LIQUID CHROMATOGRAPHY-INDUCTIVELY COUPLED PLASMA-MASS SPECTROMETRY OF ARSENIC IN MUNG BEAN SEEDLINGS USED AS A BIOINDICATOR FOR THE ARSENIC CONTAMINATION

Liquid chromatography (LC) was coupled on-line to Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to perform speciation studies of ars enic. An anion-exchange column in combination with an anion (cation) g uard column was used for the separation of six arsenic compounds: arse nite (As(III)), arsenate (As(V)), dimethylarsinate (DMA) or cacodylic acid, monomethylarsonate (MMA). arsenocholine (AsB) and arsenobetaine (AsB) using a phosphate: buffer as eluent (pH approximate to 6). The i nfluence of several parameters such as the composition of the mobile p hase and the flow rate, on the separation efficiency were first invest igated to determine the best chromatographic conditions. The coupling of LC to ICP-MS gave reproducible results with detection limits in the mu g l(-1) level and a good linearity (r>0.998) over several orders o f magnitude. The method was applied to speciate arsenic in mung bean s eedlings grown on arsenite/arsenate contaminated substrates. The resul ts of these speciation studies showed that most of the arsenic is accu mulated in the roots and that a reduction of As (V) to As (III) occurs in the roots, whereas in the leaves As occurs for a larger part as As (V). (C) 1998 Elsevier Science B.V.