A novel dispersive liquid-liquid microextraction method with high performance liquid chromatography for detection of 2,6-dimethylaniline in lidocaine hydrochloride injection

Abstract

A novel hexafluoroisopropanol (HFIP)-octanol supramolecular solvent (SUPRAS) based dispersive liquid-liquid microextraction (DLLME) method was developed for the determination of 2,6-dimethylaniline (2,6-DMA) in lidocaine hydrochloride injection coupled with high performance liquid chromatography-ultraviolet detection (HPLC-UV). n-Octanol was selected as extraction solvent while HFIP was served as dispersing agent, self-assembly inducer of n-octanol as well as density-regulating agent of n-octanol. The HFIP-octanol SUPRAS displays reverse micellar aggregate structures (2-6 μm) with hydrophilic inner cores and is located in the bottom phase of the system after phase separation, which not only facilitates the efficient extraction and enrichment of polar 2,6-DMA, but also simplifies the extraction process. Several parameters influencing the extraction efficiency of 2,6-DMA were investigated and optimized. Under optimum conditions (0.4%(v/v) n-octanol, 5% (v/v) HFIP, vortex for 3 s at 60 W, standing for 3 min, centrifugation for 3 min at 3000 r/min, sample solution pH 9), the novel DLLME-HPLC method shows good linearity for quantitative detection of 2,6-DMA in the range of 1-100 μg/L (R=0.9989). The limit of detection (LOD) was 0.33 μg/L. The enrichment factor (EF) reached about 63. Intra-day and inter-day precisions (n=3) were all below 2.5%. The recoveries were from 93.9% to 100.8%. The results demonstrate that the novel DLLME-HPLC method is suitable for the accurate quantitative determination of 2,6-DMA in lidocaine hydrochloride injection with advantages of simplicity, rapidness, high efficiency and environmental friendliness, and may own high potential in future prospects.