Studies on the use of XeF2 as digestion reagent

A digestion procedure was developed for the determination of selected eleme nts (Al, Ba, Ca, Ce, Cd, Co, Cr, Cu, Fe, La, Mg, Ni, Sr, Pb, Zn) in sedimen ts using XeF2. The use of XeF2 has some interesting features but this reage nt should be handled only under dry gas which is a severe limitation of the methodology. In a first step the sediment sample (0.1 g) is dried (120 deg rees C) and digested by XeF2 (1.5 g) in the vapor phase (190 degrees C; 9 x 10(6) Pa). Then the dry residue is dissolved in aqua regia and the solutio n digested at high pressure once again (aqua regia digestion). Subsequently the digested solution is diluted with sub-boiling distilled water and is r eady for the analysis by ICP-MS. The sediment standard CRM 320 was analyzed to verify the procedure. A comparison of the results with those obtained b y the normally used fluoric acid digestion showed that the recovery rates o f each investigated element agreed within a confidence interval of 95%, exc ept Cr. The recovery rate of Cr was lower for the XeF2 digestion than for t he fluoric acid digestion by more than 5%. Further studies were focussed on the possible digestion of SiC by XeF2 as first step for the trace element determination. In the gaseous reaction products Si could be detected by ICP -MS which gives evidence to a decomposition of SiC. A digestion procedure f or small Si samples (0.010 g) was developed. Detection limits (DL) deter mi ned for selected elements of analytical interest (Al, Ca, Cd, Cr, Co, Cu, F e, Mg, Ni, Pb) were between 1 to 12 ng/g. For most of the elements this is an improvement in comparison to the HF vapor phase digestion. The verificat ion of the method was carried out with GFAAS.