Cloud-point extraction/preconcentration on-line flow injection method for mercury determination

Abstract

A cloud-point extraction/preconcentration (CPE/P) step is incorporated on-line into a flow injection system which is used to determine low levels of Hg(II) added to natural water samples. The analyte is complexed with dithizone. A solid reagent column (SRC) is used to prepare the reagent on-line by using 5% (v/v) Triton X-100 solution as solvent. The CPE/P is carried out by using the non-ionic surfactant Triton X-100. After obtaining the cloud-point on-line, the surfactant-rich phase containing the complex is collected in a mini column packed with cotton wool. Then, a hot water stream is passed through the column to elute the complex and the absorbance is measured at 500nm. All the flow and chemical variables are optimized and the enhancement factor for the system is estimated. The calibration is linear over the range 0.05-0.5μgml -1, the R.S.D. is 4.8%, the limit of detection (signal:noise = 3) is 0.014μgml-1 and the sample throughput is 30h-1. An open/closed system is used to eliminate the interference of iron(III). © 2003 Elsevier B.V. All rights reserved.