Multielement analysis of coal by ICP techniques using solution nebulization and laser ablation

The combination of inductively coupled plasma atomic emission spectrometry and high resolution inductively coupled plasma mass spectrometry for the de termination of 70 elements in coal were studied. Four microwave-assisted di gestion procedures with different dissolution mixtures (nitric and hydroflu oric acids, aqua regia and hydrogen peroxide), lithium metaborate fusion wi th and without previous sample ashing as well as direct sampling by laser a blation (LA) have been tested. Examples of spectral interferences are given and different correction procedures are discussed. Detection limits in the low ng g(-1) range were obtained for most of the elements investigated by using high-purity reagents and by taking special care to prevent sample con tamination during preparation. The precision was assessed from replicate an alysis (including sample preparation) of coal samples and was found to be, as average values far all elements, 4-5% RSD and 10-15% RSD for procedures including sample digestion and LA sampling, respectively. The accuracy of t he overall analytical procedures was estimated by analysis of certified ref erence materials and of a coal sample obtained from the Interlab Trace roun d robin test. Among the dissolution mixtures tested, the combination of nit ric and hydrofluoric acids with hydrogen peroxide provide the best agreemen t with certified, recommended, literature-compiled or consensus values, tho ugh fusion is necessary to obtain quantitative recoveries for Si, Cr, Hf, W , Zr, Y. In general, results obtained by LA fall within +/- 20% of those ob tained after digestion. (C) 2000 Elsevier Science B.V. All rights reserved.