Salt saturated dispersive liquid-liquid microextraction of crystal violet from fish and seawater samples based on camphor-thymol based hydrophobic deep eutectic solvent optimized by response surface methodology

Abstract

A novel salt saturated dispersive liquid-liquid microextraction (SSDLLME) protocol is introduced for the extraction of crystal violet from fish and seawater samples prior to its spectrophotometric determination. As the extracting phase, a hydrophobic deep eutectic solvent based on camphor-thymol (by the mole ratio of 1:1) is employed in the sample. This is the first report of the application of SSDLLME for a dye utilizing deep eutectic solvents as extracting solvent. Saturation by salt significantly increased the performance of the microextraction; i.e. presence of salt in DLLME enhanced signals with more than 42%. Factors influencing the extraction efficiency were evaluated and optimized by both one-variable-at-a-time and response surface methodology methods. The optimum extraction condition were as: pH of sample solution 7.0; type and volume of extraction solvent (organic phase) 60 µL of camphor-thymol (1:1); 500 µL methanol as dispersive solvent; sample volume 10.0 mL; and time and rate of centrifugation 8 min and 9000 rpm, respectively. The suggested microextraction achieved a linear calibration curve in the concentration range of 1.0 to 500.0 µg L−1 with a limit of detection and quantification of 0.28 and 0.97 µg L−1, respectively. Recoveries were also suitable (≥0.97%). The total analysis time was less than 15 min and an enrichment factor of 157 was obtained. This is the first report on successful determination of crystal violet in Chabahar Bay (Oman Sea) and fishes live in the same area.