Flame atomic absorption spectrometric determination of silver ion after preconcentration on octadecyl silica membrane disk modified with bis[5-((4-nitrophenyl)azosalicylaldehyde)] as a new Schiff baseligand

Abstract

A new Schiff base ligand, bis[5-((4-nitrophenyl)azosalicylaldehyde)] (BNAS), was synthesized and a highly sensitive, selective and rapid method for the determination of silver ion was developed. It is based on the rapid extraction of silver(I) ion with BNAS adsorbed on octadecylsilica (C₁₈) membrane disk. The retained silver ion can be eluted from the disk with a minimal amount of thiosulfate solution and the silver determined with FAAS. Extraction efficiency and the influence of flow rates, type and smallest amount of stripping reagent and pH were investigated. The relative standard deviation for ten replicate extractions of silver from 1 L samples containing 2.5 µg of silver is 1.1%. The breakthrough volume for 2.5 µg of silver is 2500 mL. The effects of various cationic interferences on percent recovery of silver were studied. The re-use of a modified disk was tested and it was found that the use of the same disk modified with 7 mg of BNAS for at least ten times resulted in no change in the recovery of silver ion. The proposed method permitted large enrichment factors of about 160 and higher. The limit of detection of the proposed method is 10 ng L⁻¹ and the method is applied to the recovery of Ag⁺ from different water samples and radiology film.