Room temperature cloud point extraction: An application to preconcentration and spectrophotometric determination of copper(II)

The novel cloud point extraction procedure for preconcentration of copper(II) was discovered. A simple chemical method for initiating the cloud point extraction (CPE) has been proposed. The formation of surfactant rich phase in a system containing a nonionic surfactant Triton X-100, copper(II), 6,7-dihydroxy-4-methyl-2-phenylbenzopyrilium chloride (DHMPhB) and ammonium benzoate is observed immediately upon the sulfuric acid addition into solution. Under the optimal conditions (absorption band maximum was 540 nm, concentration 1.5×10-4 mol dm‑3 of DHMPhB, 1.0 vol.% of Triton X-100, 2.0 cm3 of 0.75 mol dm-3 ammonium benzoate, and 1.0 cm3 of 0.5 mol dm-3 sulfuric acid solution for obtaining benzoic–benzoate buffer solution with pH 4.5 and initiation immediate surfactant rich phase formation) the calibration plot for spectrophotometric determination of copper(II) was linear in the range of copper(II) concentration 0.02–0.95 µg cm−3. The limit of detection was calculated 0.006 µg cm−3. The water samples were analyzed according to a suggested procedure with satisfactory results.