Salting-Out Assisted Liquid-Liquid Extraction Of Cr (Vi) In Water Prior To Its Determination By Uv– Vis Spectrophotometry

Abstract

In this study salting out-induced liquid-liquid extraction was developed for UV-Vis spectrophotometric determination of Cr (VI) in water samples. Prior to salting out-induced liquid-liquid extraction, Cr (VI) has been reacted with a chelating agent, 1, 5-diphenyl carbazide (DPC), in an acidic medium. Then, the Cr (VI)-DPC complex formed has been extracted by the proposed method and analyzed at 540 nm monitoring wavelength. Various parameters influencing the complexation and extraction efficiency of the method were evaluated and the optimal conditions were established. Under optimum conditions, the calibration curve constructed at seven concentration points exhibited satisfactory linearity range from 0.25–2 mg/L, with coefficient of determination (R2 ) of 0.9973. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.004 mg/L and 0.015 mg/L, respectively. The LOQ of the method was below the maximum tolerable limit (MTL) of Cr (VI) in drinking water, which is 0.05 mg/L. The method also demonstrated satisfactory enrichment factor (EF), which was 5.8. The intra-day and inter-day precision studies at concentration levels (Level 1; 0.75 mg/L and level 2: 1.25 mg/L) showed that proposed method has satisfactory precision (i.e., RSD < 9.0). The recovery studies, which were performed by spiking tap, well and river water samples with the above two concentration level, showed recovery values 88.0 ± 2.5% - 97.3 ± 0.1%, which are in acceptable range. The interference studies also demonstrated Fe, Cu, V, and Cd the proposed method have negligible interferences (< 5%) up to 500 mg/L. Generally, the proposed method is simple and selective, and to be used as alternative method for analysis of Cr (VI) from water and other related matrices.