Development and Validation of a Dispersive Liquid–Liquid Microextraction Method for Metoclopramide Analysis in Pharmaceuticals and Biological Samples

A rapid and sensitive dispersive liquid–liquid microextraction (DLLME) method coupled with UV-Vis spectrophotometry has been developed and validated for the determination of metoclopramide in pharmaceutical and biological samples. The method is based on the formation of an ion-pair complex between metoclopramide and cobalt(II) thiocyanate under acidic conditions (pH = 3), followed by DLLME to efficiently preconcentrate the chromogenic complex. In the novel DLLME procedure, methylene chloride was used as the extraction solvent and acetonitrile acted as the dispersive solvent, generating a cloudy heterogeneous mixture upon injection into the aqueous sample. This facilitated extensive interfacial contact and partitioning of the metoclopramide-cobalt complex into the fine dispersed methylene chloride droplets within minutes. After centrifugation, the sedimented organic phase was analyzed at the maximum wavelength of 625 nm. Under optimal conditions, the method permitted quantification of metoclopramide from 0.25–45 µg/mL with high enrichment factors, and LOD of 0.078 µg/mL, LOQ of 0.258 µg/mL and high extraction recoveries in the range of 94–101% were obtained. The proposed DLLME-spectrophotometric methodology provides a simple, rapid and sensitive approach for routine therapeutic monitoring and quality control of metoclopramide in real samples.