ETAAS determination of Cd and Pb in plants

Simple and rapid analytical procedures for the ETAAS determination of Cd and Pb in plant (poplar, clover, plantain) leaves are described. Optimal conditions are presented for the wet digestion of plant matrices with a mixture of nitric acid and hydrogen peroxide along with optimal temperature programmes for subsequent modifier-free electrothermal determination of Cd and Pb. Slurry preparation procedures using tetramethylammonium hydroxide or a mixture of 1 mol/L HNO₃ + 1.5 mol/L H₂O₂ are proposed as another approach for rapid and accurate routine analysis of Cd and Pb in plant leaves. It has been found that single standard addition can be used for quantitative determination in the case of wet digestion ETAAS and standard addition to each analysed matrix is recommended in the case of slurry ETAAS. For all plant leaves investigated good agreement was achieved between the concentrations determined by wet digestion ETAAS and slurry ETAAS. The wet digestion method provides relative standard deviations for Cd ranging from 3% to 17% and for Pb from 2% to 16%. For the slurry method the RSD values are in the range of 4–31% for Cd and 4–30% for Pb, depending for both cases on the magnitude of the measured concentrations. Validity and versatility of the methods are verified by the analyses of standard reference materials. Received: 17 March 1997 / Revised: 2 May 1997 / Accepted: 8 May 1997