Abstract Solid sampling graphite furnace atomic ab- sorption spectroscopy (SS-GFAAS) has been used for the determination of traces of heavy metals (Cd, Pb, Cu, Cr, Ni, V and As) in barytes over a wide concentration range, e.g. Cd from 0.023 to 27.0 μg/g and Pb from 1.54 to 3509 μg/g.The necessity of determining heavy metals in commercial barytes (naturally occurring barium sulfate), a mineral important to the oil industry because of its use in drilling muds, is discussed. The problems presented by the analysis of this difficult matrix are elegantly solved by using SS-GFAAS for the direct determination of heavy metals. A high-performance graphite furnace AAS with D 2 -background correction system and a transversely heated graphite atomizer was used for the investigations. The spectrometer was combined with a mechanical sam- pling module and an ultramicrobalance. The transfer of solid samples (sample weights 0.031–0.686 mg) into the atomizer was carried out by using an optimized graphite platform as the sample carrier. Calibration curve tech- niques and standard addition methods were employed us- ing external standards (CRMs). Problems associated with signal deformations like multiple peaks, tailing or shoul- ders are also discussed and possibilities to solve the prob- lems are given. The influence of the homogeneity of solid samples on the precision and accuracy are shown in a real example. The results obtained by SS-GFAAS were com- pared with results by other methods like X-ray fluores- cence spectroscopy (XRF) and flame AAS after aqua regia microwave extraction. This study has demonstrated that SS-GFAAS is a very powerful and easy-to-use method for quick and accurate analysis of barytes. Introduction Barytes is naturally occurring barium sulfate (BaSO 4 ) which is widely used in the oil and gas industry on ac- count of its high specific gravity (4.5 g cm –3 ), chemical inertness, low abrasive properties, and low toxicity as an additive in drilling muds. The majority of drilling wastes (cuttings and drilling muds) settle to the sea bed where the heavy metals might be able to find their way into the seawater and so into the food chain of human beings and animals. That is the main reason why it is necessary to control (monitor) the heavy metal concentration in barytes. Barytes is well know for its low solubility in water and even less in seawater. Therefore, conventional wet chem- istry analysis is not the ultimate method determining trace of heavy metals in natural barytes and drilling muds. An alternative and very powerful analytical approach to wet chemical analysis is direct analysis of solids by various analytical methods. Today the solid sampling atomic absorption spectrom- etry (SS-AAS) is a routinely used analytical method of determining trace elements in biological and environmen- tal solid samples [1]. SS-AAS, especially with elec- trothermal atomization in a graphite furnace (SS-GFAAS) is characterized by several interesting advantages [2–4], such as freedom from contamination, rapid analysis and low (moderate) cost. Until about a year ago the direct analysis of solid sam- ples by GFAAS was possible only with Zeeman back- ground correction and an axially heated graphite furnace. Recently, some papers presented the application of the solid sampling technique using a new powerful SS- GFAAS instrument (AAS5 SOLID, Analytik Jena GmbH, Germany) with D 2 -background corrector and transversely heated graphite furnace [5]. In addition some applications to solid samples (CRMs, river sediments, cement, pure substances and even metals) were given [6–8]. The aim of this work was to investigate a new analyti- cal application of SS-GFAAS for a difficult and very en- vironmental relevant solid matrix (barytes). R. Nowka · I. L. Marr · T. M. Ansari · H. Müller Direct analysis of solid samples by GFAAS – determination of trace heavy metals in barytes Fresenius J Anal Chem (1999) 364 : 533–540 © Springer-Verlag 1999 Received: 9 November 1998 / Revised: 29 January 1999 / Accepted: 2 February 1999 ORIGINAL PAPER R. Nowka · H. Müller () Martin-Luther-Universität Halle Wittenberg, Fachbereich Chemie, Institut für Analytik und Umweltchemie, Geusaer Str. 88, D-06217 Merseburg, Germany I. L. Marr · T. M. Ansari University of Aberdeen, Department of Chemistry, Meston Walk, Old Aberdeen, AB24 3UE, Scotland