Selective Quantification of Trace Silver in Water Samples by Displacement Solidified Floating Organic Drop Microextraction Coupled With Electrothermal Atomic Absorption Spectrometry

In this work, a novel displacement solidified floating organic drop microextraction (D-SFODME) technique was developed and coupled with electrothermal atomic absorption spectrometry (ETAAS) for the determination of trace silver in water samples without need of any masking agents. The method involved the formation of copper diethyldithiocarbamate (Cu-DDTC), extracted from the resultant Cu-DDTC with SFODME procedure using 1-undecanol. Then, the solidified floating organic drop was transferred into a sample solution containing silver ion, and another SFODME procedure was carried out. Trace Ag+ was selectively preconcentrated using 1-undecanol through a displacement reaction between Ag+ and the preconcentrated Cu-DDTC and the floating organic drop was diluted by ethanol for ETAAS detection. Interferences from coexisting heavy metal ions with lower stability of their DDTC complexes relative to Cu-DDTC were minimized. Under the optimal conditions, the limit of detection was 4.7ngL-1 (3 sigma) for silver with a sample volume of 5.0mL, and an enrichment factor of 250 was achieved. The relative standard deviation under optimum conditions is 3.6% (n=7). The proposed method was successfully applied to determine trace silver in some environmental samples with satisfactory results.