Analytical Sciences

Multielement Determination of Cadmium and Lead in Urine by Simultaneous Electrothermal Atomic Absorption Spectrometry with an End-capped Graphite Tube

Paulo R. M. CORREIA, Cassiana S. NOMURA, and Pedro V. OLIVEIRA 

Instituto de Química, Universidade de São Paulo, C. P. 26077, CEP 05513-970, Sao Paulo, SP, Brasil

A method for the multielement determination of cadmium and lead in urine is proposed by simultaneous electrothermal atomic absorption spectrometry (SIMAAS) with an end-capped transversely heated graphite atomizer (EC-THGA). The best conditions for cadmium and lead determination were obtained in the presence of NH₄H₂PO₄ as a chemical modifier, using 500°C and 1800°C as the pyrolysis and atomization temperatures, respectively. Urine samples were diluted 1 + 4 directly in autosampler cups with a mixture of 0.125% (w/v) Triton X-100 + 2.5% (v/v) HNO₃ + 0.31% (w/v) NH₄H₂PO₄. The optimized heating program was carried out in 57 s, and the instrument calibration was done with aqueous reference solutions. The use of EC-THGA increased the sensitivity of cadmium and lead by 14% and 25%, respectively. The detection limits (n = 20, 3δ) were 0.03 μg L^-1 (0.36 pg) for cadmium and 0.57 μg L^-1 (6.8 pg) for lead. The performance of EC-THGA was acceptable up to 500 heating cycles. The reliability of the entire procedure was checked with the analysis of a lyophilized urine certified reference material. The found concentrations were in agreement with the recommended values (95% confidence level).

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