Solid Phase Extraction Utilization for Colorimetric Determination of Zinc in Waters, Food, Milk, and Biological Samples

Abstract

A highly rapid, sensitive, and selective method for the determination of zinc based on the reaction of zinc(II) with 5-amino-2-(phenyldiazenyl)phenol (ACDP) and/or 5-amino-2-(ptolyldiazenyl)phenol (ATDP) and the solid phase extraction of the Zn(II)-ACDP and/or ATDP complex with Amberlite XAD-2000 was developed, in the presence of pH = 5.6 and 6.2 using ACDP and ATDP, respectively, and Triton X-114 medium. ACDP and/or ATDP reacts with zinc to form a violet complex with a molar ratio of 2:1 (ACDP and/or ATDP to zinc). This complex was enriched by the solid phase extraction with Amberlite XAD-2000. An enrichment factor of 500 was obtained by elution of the complex from the resin with a minimal amount of isopentyl alcohol (0.2 ml). In isopentyl alcohol medium, the molar absorptivity of the complex is 1.13 × 10 6 and 1.37 × 10 6 L/mol cm at 647 and 662 nm using ACDP and ATDP, respectively, against a reagent blank prepared in a similar way without zinc. Beer's law is obeyed in the range of 5.0-160 ng/ml in the measured solution. The relative standard deviation for 10 replicate samples of 50 ng/ml level is 1.26 and 1.47%, respectively. The detection and quantification limits reaches 1.5 and 4.7 ng/ml in the original samples. The presented procedure was successfully applied for determination of zinc content in real samples such as waters, food, milk, and biological samples with satisfactory results.