Solid phase extraction and spectrophotometric determination of silver with 2-(2-quinolylazo)-5-diethylaminophenol as chromogenic reagent

A new chromogenic reagent, 2-(2-quinolylazo)-5-diethylaminophenol (QADEAP), was synthesized. A sensitive, selective and rapid method has been developed for the determination of mug/L level silver ion based on the rapid reaction of silver(I) with QADEAP and the solid phase extraction of the colored chelate with C-18 cartridge. The QADEAP reacts with Ag(I) to form a violet chelate of a molar ratio 1:2 (silver to QADEAP) in pH 3.5 - 8.0. This chelate was prconcentrated by solid phase extraction with C-18 cartridge. An enrichment factor of 100 was achieved. The molar absorptivity of the chelate is 1.30 x 10(5) L mol(-1) cm(-1) at 590 nm in measured solution. Beer's law is obeyed in the range of 0.01 - 0.6 mug/ml. The relative standard deviation for eleven replicate samples of 0.01 mug/ml is 1.15%. The detection limit is 0.02 mug/L in the original samples. This method was applied to the determination of mug/L level silver ion in water with good results.