Direct analysis of solid samples by GFAAS - determination of trace heavy metals in barytes

Solid sampling graphite furnace atomic absorption spectroscopy (SS-GFAAS) h as been used for the determination of traces of heavy metals (Cd, Pb, Cu, C r, Ni, V and As) in barytes over a wide concentration range, e.g. Cd from 0 .023 to 27.0 mu g/g and Pb from 1.54 to 3509 mu g/g. The necessity of deter mining heavy metals in commercial barytes (naturally occurring barium sulfa te), a mineral important to the oil industry because of its use in drilling muds, is discussed. The problems presented by the analysis of this difficu lt matrix are elegantly solved by using SS-GFAAS for the direct determinati on of heavy metals. A high-performance graphite furnace AAS with D-2-backgr ound correction system and a transversely heated graphite atomizer was used for the investigations. The spectrometer was combined with a mechanical sa mpling module and an ultramicrobalance. The transfer of solid samples (samp le weights 0.031-0.686 mg) into the atomizer was carried out by using an op timized graphite platform as the sample carrier. Calibration curve techniqu es and standard addition methods were employed using external standards (CR Ms). Problems associated with signal deformations like multiple peaks, tail ing or shoulders are also discussed and possibilities to solve the problems are given. The influence of the homogeneity of solid samples on the precis ion and accuracy are shown in a real example. The results obtained by SS-GF AAS were compared with results by other methods like X-ray fluorescence spe ctroscopy (XRF) and flame AAS after aqua regia microwave extraction. This s tudy has demonstrated that SS-GFAAS is a very powerful and easy-to-use meth od for quick and accurate analysis of barytes.