Ž . Spectrochimica Acta Part B 56 2001 18311843 Iridium as permanent modifier in the determination of lead in whole blood and urine by electrothermal atomic absorption spectrometry  Patricia Grinberg, Reinaldo Calixto de Campos  Department of Chemistry, Pontif ıcia Uni  ersidade Catolica do Rio de Janeiro, Rua Marques de Sao Vicente, 225, ´ ´ ˆ ˜ 22453-900, Rio de Janeiro-RJ, Brazil Received 29 May 2000; accepted 4 January 2001 Abstract The behavior of Iridium as a thermally deposited permanent modifier for the determination of lead by GFAAS was studied. The iridium coating procedure was optimized using a two-level factorial design. Using the optimized coating procedure, up to 1100 firings were possible with the same coating without sensitivity losses. The system was used in the determination of lead in whole blood and urine. A mixture of 0.1% Triton X-100 and 0.2% nitric acid was used as diluent. Pyrolysis temperature was 800°C for both matrices. Spiked, low-level samples were used for calibration. Under these conditions, no significant difference was found in comparison to the results obtained using a validated conventional modification procedure employing phosphate as modifier. Also, good agreement between found and certifiedreference values were observed in the analysis of certified and commercial quality control materials, respectively. Such agreement was observed even using a 1100 times fired Ir coated platform graphite tube assembly.  2001 Elsevier Science B.V. All rights reserved. Keywords: Electrothermal atomic absorption spectrometry; Permanent iridium modifier; Lead; Blood; Urine  This paper was presented at the 6th Rio Symposium on Atomic Spectrometry, held in Concepcion and Pucon, Chile, December ´ ´ 2000, and is published in the Special Issue of Spectrochimica Acta Part B, dedicated to that conference.  Corresponding author. Fax: 55-21-249-2966. Ž . E-mail address: rccampos@rdc.puc-rio.br R.C. de Campos . 0584-854701$ - see front matter  2001 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 5 8 4 - 8 5 4 7 01 00162-8