Selective preconcentration of silver by one-step displacement dispersive liquid–liquid microextraction and determination by graphite furnace atomic absorption spectrometry

Abstract

A simple and rapid one-step displacement dispersive liquid–liquid microextraction method (D-DLLME) was developed for the selective preconcentration of silver followed by graphite furnace atomic absorption spectrometry determination. In the proposed method, Cu was reacted with diethyldithiocarbamate (DDTC) to form a Cu–DDTC complex, and it was used as a chelating agent instead of DDTC for dispersive liquid–liquid microextraction (DLLME) of silver. Because the stability of Ag–DDTC is higher than that of Cu–DDTC, Ag can displace Cu from the Cu–DDTC complex and be preconcentrated in a single DLLME procedure. Potential interference from co-existing metal ions with lower DDTC complex stability was largely eliminated as they cannot displace Cu from the Cu–DDTC complex, and the tolerance limits for these ions were improved by a long way compared with the conventional DLLME method. Under the optimal conditions, the limit of detection of this method was 16 ng L⁻¹ (3σ) for silver, and an enhancement factor of 82 was achieved with a sample volume of 5.0 mL. The proposed method was successfully applied for the determination of trace silver in some environmental and biological samples with satisfactory results.