Method validation for the determination of lead in raw cow's milk by electrothermal atomic absorption spectrometry

In this study, lead in raw cow's milk has been determined by validated electrothermal atomic absorption spectrometry (ETAAS) with Zeeman-effect background correction. Maximum pyrolysis and optimum atomization temperatures of lead were determined in the presence of modifiers. Pd + Mg(NO3)2 has been found a powerful modifier mixture for the determination of lead. The analytical parameters of the method such as limit of detection, limit of quantification and the effect of interfering ions have been investigated. The detection limit (3sigma) achieved by the method was calculated to be 0.62 ng/mL for Pb. Repeatability of the method evaluated as the relative standard deviation of 16-17 replicates using 5 ng/mL, under optimum experimental conditions were about 1.5% for synthetic sample solution and about 3% for real sample (N = 5). The described method has been validated by analyzing certified reference material (BCR-CRM 150) and by comparing the results with those obtained by inductively coupled plasma mass spectrometry (ICP-MS). The validated method was applied to raw cow's milk samples produced in 7 different regions of Turkey in 2003-2004. Raw cow's milk contained a mean (range) of 31.4 (2.5 - 313) microg kg(-1) lead with a relative error below 2%.