(318a) Solid Phase Extraction for Heavy Metals Prior to Atomic Absorption Spectroscopy

Heavy metals are important constituents widely used in different industrial processes for production of various synthetic materials. For evaluation of workers' exposure to trace toxic metals, including Pb, Hg, Cr, Cd, Co, Ni and Cu environmental and biological monitoring are essential processes, in which, extraction of the metals from dirty environmental and biological samples is one of the most time-consuming and error-prone aspects prior to atomic absorption spectrometry. In these days, the use of solid-phase extraction (SPE) is becoming most popular and has grown as this versatile technique is a fertile approach in sample preparation methodologies, so that, it provides better results than those produced by low efficient liquid-liquid extraction (LLE) method. To evaluate different factors influencing quantitative and trace analysis scheme of toxic metals, solid phase extraction using minicolumns filled in our laboratory with different sorbents, including various Chromosorbs (102, 105) and XAD resins (2, 4, and 7) was optimized with regard to sample pH, ligand concentration, loading flow rate, elution solvent, elution flow rate, sample volume (up to 750 ml), elution volume, amount of resins, and sample matrix interferences. Trace metal ions were efficiently retained on different solid sorbents and were eluted simultaneously with 10-20 ml 1M and 2M HNO3 (for Hg 1 M HCl) followed by simple determination of analytes by using flame atomic absorption spectrometery. Obtained recoveries of metal ions were more than 96% (for Hg 80%). The amount of the analytes detected after simultaneous preconcentration were basically in agreement with the added amounts. Generally, urine can be considered as a rutine index of occupational and environmental exposure for evaluation of such pollutants, therfore, the optimized procedure was also validated with three different pools of spiked urine samples and showed a good reproducibility over six consecutive days as well as six within-day experiments. From the results obtaind during our experimantal design, it can be concluded that, the developed method is promising to be applicable for evaluation of other metal ions present in different environmental and biological samples as suitable results were obtained for relative standard deviation (less than 10%), therefore, this optimized method can be considered to be successful in simplifying sample preparation for trace residue analysis of heavy metals in different matrices for evaluation of occupational and environmental exposures.