Amorim Fábio A C, Ferreira Sérgio L C
Instituto de Química, Núcleo de Excelência em Química Analítica da Bahia, Grupo de Pesquisa em Química Analítica, Universidade Federal da Bahia, Campus Universitário de Ondina, Salvador 40170-290, Bahia, Brazil.
Talanta. 2005 Feb 28;65(4):960-4. doi: 10.1016/j.talanta.2004.08.027.
In the present paper, a simultaneous pre-concentration procedure for the sequential determination of cadmium and lead in table salt samples using flame atomic absorption spectrometry is proposed. This method is based on the liquid-liquid extraction of cadmium(II) and lead(II) ions as dithizone complexes and direct aspiration of the organic phase for the spectrometer. The sequential determination of cadmium and lead is possible using a computer program. The optimization step was performed by a two-level fractional factorial design involving the variables: pH, dithizone mass, shaking time after addition of dithizone and shaking time after addition of solvent. In the studied levels these variables are not significant. The experimental conditions established propose a sample volume of 250mL and the extraction process using 4.0mL of methyl isobutyl ketone. This way, the procedure allows determination of cadmium and lead in table salt samples with a pre-concentration factor higher than 80, and detection limits of 0.3ngg(-1) for cadmium and 4.2ngg(-1) for lead. The precision expressed as relative standard deviation (n = 10) were 5.6 and 2.6% for cadmium concentration of 2 and 20ngg(-1), respectively, and of 3.2 and 1.1% for lead concentration of 20 and 200ngg(-1), respectively. Recoveries of cadmium and lead in several samples, measured by standard addition technique, proved also that this procedure is not affected by the matrix and can be applied satisfactorily for the determination of cadmium and lead in saline samples. The method was applied for the evaluation of the concentration of cadmium and lead in table salt samples consumed in Salvador City, Bahia, Brazil.
本文提出了一种使用火焰原子吸收光谱法同时预富集测定食盐样品中镉和铅的方法。该方法基于镉（II）和铅（II）离子作为双硫腙配合物的液-液萃取，并将有机相直接吸入光谱仪。使用计算机程序可以依次测定镉和铅。通过涉及以下变量的二级分式析因设计进行优化步骤：pH值、双硫腙质量、加入双硫腙后的振荡时间以及加入溶剂后的振荡时间。在所研究的水平下，这些变量并不显著。所确定的实验条件建议样品体积为250mL，并使用4.0mL甲基异丁基酮进行萃取过程。通过这种方式，该方法能够测定食盐样品中的镉和铅，预富集因子高于80，镉的检测限为0.3ng/g，铅的检测限为4.2ng/g。以相对标准偏差（n = 10）表示的精密度，对于镉浓度为2和20ng/g时分别为5.6%和2.6%，对于铅浓度为20和200ng/g时分别为3.2%和1.1%。通过标准加入技术测量的几个样品中镉和铅的回收率也证明了该方法不受基质影响，可令人满意地应用于盐样品中镉和铅的测定。该方法用于评估巴西巴伊亚州萨尔瓦多市消费的食盐样品中镉和铅的浓度。
