Determination of Heavy Metals in Environmental Samples by Micro Atomic Absorption Spectrometry with Solid Sample Introduction

Atomic spectrometric techniques are in widespread use for determining trace metals in many sample types. A major disadvantage, however, is the need generally to present samples in a liquid form to the instrument. Common sample preparation procedures are dry ashing followed by dissolution of the inorganic residue in dilute mineral acid or wet digestion with oxidizing acids. Dry ashing is slow and may lead to losses of volatile elements, and wet digestion is hazardous, often requiring treatment with hydrofluoric and perchloric acids to completely dissolve the matrix. Previous work in this laboratory led to the development of a rapid microsampling-cup atomic absorption method for determining lead in vegetation. The dried vegetation was powdered and made into an aqueous slurry which was pipetted directly into the sampling cups. No further treatment was required prior to sample atomization. This work has been extended to enable very small segments (a few mg) of a plant to be analyzed individually. The modified analytical technique will be described and it will be shown how the distribution of lead, at normal levels, through a single plant can be determined. Preliminary results demonstrated that lead can be determined in soil by introducing slurries directly into a graphite furnace electrothermal atomizer. Further work will be presented to show that good correlation with a total digestion procedure (hydrofluoric/perchloric/nitric acids) is achieved. The technique is being applied to determinations of other metals, and results obtained for various soil types will be presented