Schiff’s bases complexation and solid phase extraction for improved trace element analysis
An analytical method based on the separation/pre-concentration of metal ions using solid sorbents coated with Schiff’s bases has been proposed. Four Schiff’s bases have been used in the study of the three environmental related and important elements Cd, Cu, and Zn. Different factors, including the pH of the sample solution, the sample volume, and the amount of the Schiff’s base were examined to optimize the conditions for the pre-concentration of these metal ions in aqueous solutions. A pre-concentration factor of 100 was obtained. The interference effects of the additional ions in the solution have been studied, metal ions of Mg2+, Ca2+, Sr2+, Ba2+, Ag+, Pd2+, V4+, and V5+ and anions, Cl-, CO32-, SO42-, and acetate. The improved LODs are 0.007, 0.362, and 0.102 ng/ml for Zn, Cd, and Cu respectively. The improved LODs are much lower than the LODs of FAAS and approaching the LODs of GFAAS. All sorbents undergo Lanmuir isotherm. The system has been used for ultra trace element analysis of Cd using GFAAS as a detection system. Pre-concentration factor of 1334 has been achieved which means a LOD of 0.005ng/L. The effect of the structure of the solid support on the adsorption of Zn ion has been also studied. Aminopropyl silica and C18 polar plus were taken as solid supports. The capacity sequence was as following Aminopropyl silica.> Silica gel> C18 polar plus silica. The improved detection limits of SPE-FAAS for Zn using those sorbents have been found to be 0.007, 0.016, and 0.0237 ng/ml for silica gel, C18 polar plus silica, and aminopropyl silica respectively. The newly developed procedure SPE-FAAS has been found to be successful in separating the complex matrices (hair, vitamin tablets, and water) and pre-concentrating Zn and Cd ions from relatively large sample volume. The developed method for solid – liquid extraction is convenient, simple, sensitive and of low costs.