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.
