Trace Analysis of Niflumic Acid in Milk and Human Plasma by Ion-pair-based Vortex Assisted Dispersive Liquid-liquid Microextraction Combined with UV-Vis Spectrophotometry

A simple, accurate and fast vortex-assisted dispersive liquid-liquid microextraction procedure has been developed for the extractive spectrophotometric determination of niflumic acid in biological samples. The method is based on the formation of an ion association complex between niflumic acid and methylene blue. The resulting ion-pair was extracted into dichloromethane and its absorbance was measured at 655 nm. All experimental parameters affecting the analytical performance of the method such as pH, type and volume of buffer and extraction solvent, dye concentration, extraction time, ionic strength and interfering species were investigated. The calibration curve was linear in the range of 5-70 ng mL-1 and the limit of detection (LOD) was found to be 2.8 ng mL-1. The procedure was successfully applied for the determination of niflumic acid in human plasma and goat’s milk samples. The main advantages of the proposed method are rapidity, little solvent consumption, low cost and providing low LOD by the simple UV-Vis spectrophotometer.