Determination of cadmium and lead at low levels by using preconcentration at fullerene coupled to thermospray flame furnace atomic absorption spectrometry

Abstract

A new and sensitive method for Cd and Pb determinations, based on the coupling of thermospray flame furnace atomic absorption spectrometry and a preconcentrator system, was developed. The procedure comprised the chelating of Cd and Pb with ammonium pyrrolidinedithiocarbamate with posterior adsorption of the chelates on a mixture (40 mg) of C 60 and C 70 at a flow rate of 2.0 ml min −1. These chelates were eluted from the adsorbent by passing a continuous flow of ethanol (80% v/v) at 0.9 ml min −1 to a nickel tube placed in an air/acetylene flame. After sample introduction into the tube by using a ceramic capillary (0.5 mm i.d.), the analytical signals were registered as peak height. Under these conditions, improvement factors in detectability of 675 and 200 were obtained for Cd and Pb, respectively, when compared to conventional flame atomic absorption spectrometry. Spiked samples (mineral and tap waters) and drinking water containing natural concentrations of Cd were employed for evaluating accuracy by comparing the results obtained from the proposed methodology with those using electrothermal atomic absorption spectrometry. In addition, certified reference materials (rye grass, CRM 281 and pig kidney, CRM 186) were also adopted for the accuracy tests. Due to the good linearity ranges for Cd (0.5–5.0 μg l −1) and Pb (10–250 μg l −1), samples with different concentrations could be analyzed. Detection limits of 0.1 and 2.4 μg l −1 were obtained for Cd and Pb, respectively, and RSD values <4.5% were observed ( n=10). Finally, a sample throughput of 24 determinations per hour was possible.