Atomic fluorescence determination of inorganic arsenic in soils after microwave-assisted distillation

An inexpensive microwave-assisted distillation procedure has been developed for quantitative determination of inorganic arsenic in soils by atomic flu orescence spectrometry (AFS). After reduction of As(V) to its trivalent sta te with potassium iodide, inorganic arsenic was distilled as AsCl3 that was finally determined by atomic fluorescence after hydride generation with Na BH4 in HCl medium. The different parameters that control the distillation: concentration and volume of HCl, time of distillation, sample weight, and o ven load, win studied. The methodology developed has a detection limit of 0 .015 mu g l(-1) which corresponds to a concentration of 0.006 mu g of As pe r gram of soil, and a relative standard deviation of 3% for nine independen t analyses of the same soil sample containing 8.7 mu g g(-1) As. The recove ry percentage of As(III) and As(V) were 103 +/- 4 and 106 +/- 4%, respectiv ely, Total arsenic was determined after microwave-assisted digestion, ender pressure, with HCl : HNO3 (3 : 1)/H2O2 in hermetically sealed Teflon react ors. By introducing an additional microwave-assisted digestion step after d istillation of inorganic arsenic, the organic fraction of arsenic in soils and sediments was established. (C)2000 Elsevier Science B.V. All rights res erved.