An air-assisted liquid–liquid extraction using a dual-valve sequential injection manifold (DV-SIA): Determination of copper

Abstract

This work introduces an approach to liquid–liquid extraction for the sequential injection technique by improving on a previously reported dual-valve sequential injection manifold (DV-SIA). The system is made up of three units: a Mixing unit (for aqueous phase only), an Extraction unit, and a Detection unit (for organic phase only). The extraction was carried out by controlled aeration in the Extraction unit. The efficiency of the suggested extraction procedure was demonstrated by the spectrophotometric determination of copper extracted as an ion associate of Cu(I) with the polymethine dye 1,3,3-trimethyl-2-[5-(1,3,3-trimethyl-1,3-dihydroindol-2-ylidene)-penta-1,3-dienyl]-3H-indolium (DIDC). Appropriate experimental conditions were found to be: 40 μL of 2 mol L⁻¹ NaCl; 50 μL of sample, 20 μL of 1 mmol L⁻¹ DIDC (pH 3), flow rate 50 μL s⁻¹. A linear response was obtained in the range 0.13–2.0 μg mL⁻¹ of Cu, and the limit of detection, calculated based on three times the standard deviation of the blank test (n = 10), was 0.02 μg mL⁻¹. The method was applied to an assay of copper in pharmaceutical materials.