NOVEL LASER SAMPLING TECHNIQUE FOR INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY

A novel laser sampling technique, back-surface ablution, has been deve loped for ICP-AES, Samples are coated onto a transparent substrate and a laser beam is irradiated onto the sample through the substrate inst ead of sampling directly from the sample surface, As part of the sampl e is vaporized by the laser beam, a high pressure develops at the samp le-substrate interface, The sample at the laser spot is explosively an d completely removed by the expanding vapour, Sampling efficiency is u p to ten times higher than conventional 'front-surface' laser sampling , Also, preferential vaporization is minimized because of complete rem oval of the sample at the laser spot, The risk of inaccurate chemical analysis associated with non-stoichiometric thermal vaporization in fr ont surface laser sampling is reduced, Two methods of calibration, viz ., standard additions and calibration with standards in a poly(vinyl a lcohol) matrix, were used for quantitative elemental analysis of house hold paints using front- and back-surface ablation-ICP-AES, Internal s tandards were used to compensate for pulse-to-pulse laser energy fluct uation and sample thickness variation across a sample, Ten elements wi th different thermal properties and at concentrations ranging from 10 to 1000 ppm were determined and the elemental concentrations were comp ared with those of microwave digestion/solution nebulizaiion-ICP-AES. Back-surface ablation appears to be more accurate than conventional fr ont-surface ablation.