Graphene Oxide/Plane Cocoon Double Membrane Solid Phase Microextraction for the Concentration of Alkaloids in Coptis chinensis

A new graphene oxide/plane cocoon double membrane solid phase microextraction, combined with HPLC, was proposed and employed for concentration and determination of the trace levels of four alkaloids (jatrorrhizine, coptisine, palmatine and berberine) in Coptis chinensis. In this method, a special double solid membrane was prepared to extract four alkaloids. After extraction, the enriched target analytes on the membrane were dissociated by methanol and analyzed by HPLC. The main variables affecting the method were investigated and optimized. Under the optimized conditions, linear range of coptisine was 0.005–1.5 µg mL⁻¹, the other three were 0.001–1.5 µg mL⁻¹; limit of detection and limit of quantification of jatrorrhizine, coptisine, palmatine, berberine were 0.3, 1.0, 0.1, 0.2 ng mL⁻¹and 0.8, 1.5, 0.8, 0.7 ng mL⁻¹, respectively; EFs of four alkaloids were 108, 85, 112 and 122, respectively. Furthermore, the relative standard deviations of intra-day and the inter-day were 1.2–4.6% and 5.7–10.4%, respectively. The average recoveries were 95.1–105.0%. Also, the microextraction mechanism was described. The results demonstrated that this approach is a simple and reliable, and can be used to help establish sensitive quality control methods of the active compounds in C. chinensis.