ultra-trace determination of silver in water, soil and radiology film samples using dispersive liquid-liquid microextraction and microvolume uv–vis spectrophotometry

In this research, a dispersive liquid-liquid microextraction (dllme) method coupled to uv-vis spectrophotometry was developed for the indirect determination of silver ion. the method is based on the catalytic effect of the silver ion on the oxidation of congo red by potassium peroxodisulphate and extraction with dllme procedure using chloroform (extraction solvent) containing cetyltrimethyl ammonium bromide which provides counter ion and also acts as a disperser. after extraction, the phase separation is performed with a centrifugation, and the silver ion is determined in the enriched phase by uv-vis spectrophotometry. several factors affecting the microextraction efficiency, such as ph of the solution, extraction time, type and volume of extraction solvent were investigated. under optimum conditions, a linear calibration graph in the range of 0.5-105.0 ng/ml of silver ion in the initial solution with r^2 = 0.9987 (n=10) was obtained. detection limit of method was 0.2 ng/ml and the relative standard deviation (rsd) for 3 and 70 ng/ml of silver ion was 3.5 and 1.7 (n=10), respectively. the enrichment factor was 54. the method was successfully applied to the determination of trace amounts of ag(i) in radiology film and environmental matrices.