ULTRASONIC SLURRY SAMPLING GRAPHITE FURNACE ATOMIC ABSORPTION SPECTROMETRY - ANALYTICAL CONSIDERATIONS FOR ANALYSIS OF A HIGH DENSITY GLASS MATERIAL

摘要

A high density borosilicate glass reference material was distributed to collaborators participating in a collaborative study to evaluate the state-of-the-art of solid sampling. Several collaborators reported low values for Cr in the reference glass material, U.S. Geological Survey GSD, as compared with the reference concentration of 46.5 +/- 9.2 mu g g(-1). On average, results were 20% low as compared with the mean reference concentration, but some labs reported results which were nearly 50% low. In consequence, the glass sample was evaluated and its physical properties were characterized, including particle size distribution and density. Also, a systematic evaluation of analysis parameters was conducted, including: slurry preparation, analysis volume, pipetting accuracy, and sampling depth. The data suggest that the low analytical values are most likely the result of sedimentation errors with this high density (2.6 g cm(-3)) material. Studies suggest that an optimum sampling depth for this high density material is approximately 10 mm below the surface. The feasibility of reducing particle size by grinding the glass material to < 38 mu m to allow sampling at a range of depths is also demonstrated. (C) 1997 Elsevier Science B.V. [References: 11]