Cr(VI) has carcinogenic effects, so determination of trace amount of chromium in human body such as urine has a great deal of importance. In this work, a novel microextraction method was developed based on solidification of dispersed fine droplets (SDFD) of a low melting point deep eutectic solvent (DES), produced with the aid of sonication, for fast and efficient determination of Cr(VI) in urine samples. Cr(VI) contents of the human urine samples were first complexed using 1,5-diphenylcarbazone at pH ≈ 2.0 and then extracted by the method. A cloudy solution was achieved by the sonication of a microliter volume of a new water-immiscible DES consisting of benzyltriphenylphosphonium bromide (BTPPB) and phenol. Low freezing point of DES makes it possible to use simple, precise, and fast collection of the extraction phase by solidification and the subsequent centrifugation. Finally, the sedimented phase was diluted with methanol and analyzed by electrothermal atomic absorption spectrometry (ETAAS). The influences of the main factors on the efficiency of the procedure were investigated by a four-factor central composite design (CCD). Under the optimum conditions, the calibration curve was linear within the range of 10-1000 ng L-1. The intra- and inter-day RSD% values of 2.6 and 4.7% were obtained at the concentration of 50.0 ng L-1, respectively. The limits of detection (LOD) and quantification (LOQ) were calculated as 2.0 and 7.0 ng L-1, respectively. Moreover, compared to the other approaches, the proposed method presented better or comparable analytical performance and provided accurate, precise, and reliable results for trace analysis of Cr(VI) in urine samples.
Keywords: Benzyltriphenylphosphonium bromide; Chromium; Deep eutectic solvent; Microextraction; Solidification; Ultrasound.