Development of a novel stirrerliquid/solid microextraction method for the separation and enrichment of trace levels of active compounds in traditional Chinese medicine.

A novel stirrer-liquid/solid microextraction method was developed for the separation and enrichment of trace levels of curcumin, bisdemethoxycurcumin, and demethoxycurcumin in Rhizoma Curcumae Longae, Radix Curcumae, and Rhizoma Curcumae before their analysis by high-performance liquid chromatography with ultraviolet detection. In the proposed approach, a magnetic stirrer was immersed in decanol to coat its surface completely with decanol, which was used as an extraction platform. The stirrer coated with decanol is not only a power to agitate the sample solution to constantly update the sample on the stirrer surface but also it can adsorb and extract the target analytes. Some effective parameters, including suitable superficial area of stirrer, extraction solvent, sample phase pH, NaCl concentration, stirring rate, extraction time, sample phase volume, were analyzed and selected. Under the optimal conditions, the linearities are 0.0044-2.20 μg/mL, detection limits are 0.3-0.6 ng/mL, and the extraction content per unit length and enrichment factors of the target analytes are 6.24-9.71/mm and 589-917, respectively. Also, the stirrer-liquid/solid microextraction mechanism for the extraction and enrichment of the target analytes was analyzed and expounded. The results showed that stirrer-liquid/solid microextraction is a simple, rapid sample pretreatment approach with a high enrichment factor.