One-Pot Separation and Preconcentration for the Determination of Chromium Species Using an Aqueous Biphasic System

Abstract

The widespread use of the trace metal chromium in industrial processes and the known toxicity of CrVI species have stimulated interest in chromium speciation analysis. However, some analytical detection systems are not suitable for the quantification of CrIII and CrVI species. In the present study, an aqueous biphasic system (ABS) was employed as an environmentally safe, simple, and economical alternative. The ABS allows the implementation of an efficient separation step before quantifying of the species of interest by flame atomic absorption spectrometry. A robust speciation and preconcentration method was developed, which can be applied to samples with a wide concentration range, without the use of any extractants and interconversion of the species during the procedure. The proposed method was successfully used to determine the chromium species present in tap, treatment plant, river, and electroplating wastewater samples. Recovery percentages of 87.9-107% were achieved, suggesting minor water matrix interference. The proposed method had acceptable limits of detection and quantification of 5.38 and 16.3 μg kg-1, respectively.

Atomic spectrometry update: review of advances in elemental speciation

“…A procedure for the separation of Cr species in water samples into two aqueous phases has been devised for determination by FAAS. 72 The two phases were created by adding to the acidified sample sufficient amounts of poly(ethylene oxide), average molar mass 1500 g mol −1 (PEO1500), and Na 2 SO 4 such that after centrifuging, sitting, and warming (25 °C, 20 min), two phases formed consisting of a top phase containing 43.41% (m/m) PEO1500 and 1.46% (m/m) Na 2 SO 4 and a bottom phase containing 1.03% (m/m) PEO1500 and 21.71% (m/m) Na 2 SO 4 . Preconcentration was achieved for Cr VI the species predominantly extracted into the top phase, as the volume of top phase was considerably smaller than the original sample volume when analysing tap water, local wastewater treatment plant effluent, and Piracicaba River water.…”

“…Without any further optimisation, almost baseline resolution of the peaks for arsenate, chromate and molybdate was obtained. The spectrometer was operated in collision mode with He as the bath gas and 4 ISs, 72 Ge, 115 In, 103 Rh, 45 Sc, were added to the mobile phase at concentrations of 100 ng mL −1 . Total element concentrations were also measured by ICP-MS, the procedure for which was validated by the analysis of SPS Spectrapure Standards AS (Oslo, Norway) SPS-SW1 (quality control material for surface water analysis).…”