Salt-assisted dispersive liquid-liquid microextraction for enhancing the concentration of matrine alkaloids in traditional Chinese medicine and its preparations.

A fast, simple, and efficient salt-assisted dispersive liquid-liquid microextraction coupled with high-performance liquid chromatography was developed and introduced for the simultaneous enrichment, extraction, and determination of the trace levels of matrine alkaloids (sophoridine, matrine, and sophocarpine) in Sophorae Flavescentis Radix and Composite Kushen injection. Compared with conventional dispersive liquid-liquid microextraction, the proposed method, with added salt but without dispersant and centrifuging, makes the operation simpler, greener, and leads to a higher enrichment factor. The crucial parameters affecting the enrichment factors of target analytes, such as type and volume of extraction solvent, pH of sample phase, salt concentration, volume of sample phase, and extraction time, were investigated and optimized, meanwhile, the extraction mechanism of the method was analyzed and described. Under the optimized conditions, the enrichment factors of the three matrine alkaloids were 150, 178, and 227, respectively. Good linearities (r ≥ 0.9992) for all analytes, low limits of detection (less than 0.08 ng/mL), satisfactory precisions (2.1-12.3%), and accuracies (recoveries, 99.3-103.9%) were achieved. The experimental results showed that the approach is a simple, fast, green, eco-friendly, and sensitive method and can be used for the preconcentration and determination of matrine alkaloids in traditional Chinese medicines and their preparations.