Extraction—spectrophotometric determination of copper(II) with 4-(2-pyridylazo)resorcinol and a long-chain quaternary ammonium salt

Abstract

A simple and highly sensitive extraction—spectrophotometric determination of copper (II) is described. The ion-associate formed between the copper(II)—4-(2-pyridylazo)-resorcinol (PAR) anion and tetradecyldimethylbenzylammonium chloride (TDBA) is extracted with chloroform at pH 9.7. The absorption maximum of the extracted species occurs at 510 nm, the molar absorptivity being 8.05 (± 0.07) × 10 4 l mol -1 cm -1. Beer's Law is obeyed in the concentration range 0.1–0.5 μg Cu ml -1. The composition of the ion-associate is estimated to be [Cu(PAR) 2(TDBA) 2]. The conditional extraction constant is log K' ex ≈ 8. The interference of some cations and anions is studied. The method is suitable for analysis of waters.