Slurry Sampling Graphite Furnace Atomic Absorption Spectrometry in Environmental Analyses

Abstract

AbstractSlurry sampling graphite furnace atomic absorption spectrometry (GFAAS) is a powerful tool for the determination of trace elements in environmental samples owing to its high sensitivity, instrumental simplicity, and relatively low cost. In this technique, discrete aliquots of the slurry or suspension are deposited in a graphite tube and then electrically heated to produce atomic vapors. The absorption of the atomic vapor is measured, typically with a hollow cathode lamp (HCL) or electrodeless discharge lamp (EDL), to determine the amount of analyte present in the sample. To ensure that a representative portion of the slurry is injected into the furnace, the slurry must be stabilized or mixed immediately prior to analysis. Slurry sampling GFAAS detection limits (DLs) are typically in the range of 10−2to 1 part per million (pg absolute DLs). Precision (0.5–5%) and accuracy are also good, provided that proper guidelines for slurry preparation and instrument operation are followed, and samples are sufficiently homogeneous. An additional benefit of the technique is that matrix interferences are typically small; in fact, aqueous calibration standards are routinely used in the analysis of slurry samples. A limitation of slurry sampling GFAAS is that it is primarily a single‐element technique, although continuum source and sequential atomic absorption spectrometry (AAS) systems have been developed. Furthermore, the linear range is typically less than two orders of magnitude unless alternative wavelengths, or some other means of reducing sensitivity (e.g. minigas flow during atomization), are used. In addition, some environmental samples have to be ground if the sample is not in the proper form or if the analyte is not homogeneously distributed. Care must be taken during the grinding process to avoid contamination of the sample or fractional distribution of the analyte.