Some observations on the spectrophotometric determination of zinc with 1-(2-pyridylazo)-2-naphthol, diphenylguanidine, and cetyltrimethylammonium bromide, in chloroform

Abstract

A spectrophotometric method for the determination of zinc is proposed. The metal reacts with 1-(2-pyridylazo)-2-naphthol (PAN) and diphenylguanidine (DFG) in the presence of Cetyltrimethylammonium bromide (CTAB) to form an orange ternary complex that can be extracted into chloroform. The optimum conditions for zinc extraction are pH 10 (borate buffer), 5 × 10 −4 M PAN, 0.2 M DFG, and 0.045% CTAB. The absorbance is measured at 555 nm (σ = 60,000 liters mol −1 cm −1) and Beer's law is obeyed up to 1.2 μg ml −1 zinc. The interference of five compounds is studied and the method is used to determine zinc in polyvinyl chloride stabilizers and zinc organic salts.