An automated system for liquid–liquid extraction based on a new micro-batch extraction chamber with on-line detection: Preconcentration and determination of copper(II)

Abstract

An automated system to perform liquid–liquid extraction is proposed, in which the effective mixture (the intimate contact) between the aqueous phase and the organic phase, as well as the separation of the phases, are carried out in a micro-batch glass extraction chamber. Sample, reagents and organic solvent are introduced into the glass extraction chamber by a peristaltic pump using air as carrier. The detection of the extracted species from the aqueous phase is made in a small volume (120–150 μl) of isobutyl methyl ketone (MIBK). The system allows enrichment factors of 2–10-fold. The proposed automatic system was evaluated for Cu(II) extraction based on complex formation between copper(II) and 1-(2′-pyridylazo)naphthol (PAN) in MIBK. When a volumetric ration of 2:1 (aqueous:organic) was implemented, copper was detected in the concentration range of 100–1600 μg l −1 ( r = 0.9995) with a relative standard deviation of 2% (200 μg l −1, n = 5) and a detection limit of 20 μg l −1. The analytical curve was linear over the concentration range 25–500 μg l −1 ( r = 0.9994) when a volumetric ratio of 10:1 was employed. With this ratio, the detection limit was 5.0 μg l −1 and the relative standard deviation was 6% (50 μg l −1, n = 5).