Ultrasound-Assisted Low-Density Solvent-Based Dispersive Liquid-Liquid Microextraction Coupled to Spectrophotometry for the Determination of Low Levels of Histamine in Fish and Meat Products
In this study, a new low-density solvent-based dispersive liquid-liquid microextraction strategy coupled to spectrophotometry has been developed for the determination of the trace levels of histamine in fish and meat products. The method is based on the formation of a charge transfer complex between a histamine and a phenothiazine group dye, promethazine (PMZ) in the presence of greener ionic liquid (IL), 1-butyl-3-methylimidazilium octylsulfate, C(4)mim octylOSO(3), exhibiting a surfactant-like micellar behavior at pH 7.0, and then microextraction of the complex into the floating organic drops of 1-heptanol, which is water-immiscible and lighter than water. Ultrasound or sonication was used to improve the microextraction efficiency as well as to reduce the analysis time and cost. Variables affecting the microextraction efficiency were evaluated and optimized. Under optimal conditions, a calibration plot, which is prepared from solvent-based calibration solutions, was linear in the range of 5-750gL(-1), with a sensitivity enhancement of 95-fold. In addition, the satisfactory extraction recoveries ranging from 95.2 to 102.8% were obtained. The method has been found to have excellent detection sensitivity, with a detection limit of 1.35gL(-1) and intra- and inter-day precisions of 3.5-5.6% (as RSDs; n, 5 and 3x5). A preconcentration factor of 107-fold from the preconcentration of a 75-mL sample was obtained. The method was statistically validated by analysis of two quality control samples, including accuracy and precision studies after spiking. The method may be accepted as a simple, easy-to-use, low-cost, fast, sensitive, accurate, and reliable approach, even better than conventional DLLME and similar techniques. The results indicated that this methodology was suitable for the analysis of low levels of histamine in selected food matrices.