Determination of Trace Amount of Silver by Atomic-Absorption-Spectrometry-Coupled Flow Injection On-Line Coprecipitation Preconcentration Using DDTC–Copper as Coprecipitate Carrier

A flow injection on-line coprecipitation preconcentration system with diethyldithiocarbamate (DDTC) chelate of copper used as the coprecipitate carrier was coupled with flame atomic absorption spectrometry (FAAS) for the determination of trace silver. Silver was on-line coprecipitated with DDTC-Cu(II) in 0.5 moL · L⁻¹HCl, and the precipitate was collected in a knotted reactor. The precipitate was then dissolved by isobutyl methyl ketone and transported directly into the nebulizer–burner system of a flame atomic absorption spectrometer. A detection limit (3ς) of 0.6 μg · L⁻¹was achieved for a loading period of 30 s, a relative standard derivation of 2.0% was obtained for 11 determinations of 20 μg · L⁻¹Ag(I). Interference-free levels were 10 mg · L⁻¹for Cd²⁺, 50 mg · L⁻¹for Cu²⁺, 50 mg · L⁻¹for Mn²⁺, 25 mg · L⁻¹for Ni²⁺, 100 mg · L⁻¹for Pb²⁺, 50 mg · L⁻¹for Zn²⁺, 500 mg · L⁻¹for Fe³⁺, and 2000 mg · L⁻¹for Fe²⁺reduced from Fe³⁺by ascorbic acid. The developed method has been successfully applied to the determination of trace amount of silver in geological samples.