[Determination of higenamine in Chinese herbal medicine, condiments, and topical medicine by QuEChERS combined with liquid chromatography-tandem mass spectrometry].

A method combining QuEChERS with liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for the determination of higenamine in Chinese herbal medicine, condiments, and topical medicine. The sample was subjected to extraction using a formic acid-ethanol mixture, followed by purification of the QuEChERS sorbents; then, the extraction solution was introduced into the LC-MS/MS system for detection in multiple reaction monitoring (MRM) mode. Under the optimal conditions, the detection limit of the developed method was 0.03 ng/g, and the linear range was 0.10-100 ng/g with a relative standard deviation (RSD) of 4.33% (0.5 ng/g, n=7). The method was then applied to the determination of higenamine in 13 kinds of Chinese herbal medicine, four kinds of condiments, and a topical medicine. Higenamine was detected in dried lotus leaf, dried lotus seed, Chinese yam, Yuzhu, Yam, Sichuan pepper, Cassia, and the topical medicine at 9667.6, 1183.8, 21.5, 8.2, 8.5, 148.6, 21.3, and 173.3 µg/kg, respectively. The recoveries of higenamine in Sichuan pepper and cassia was 92.6%-109.8%. In conclusion, the method is fast, simple, reliable, and suitable for use in batch operation.

Preparation of Molecularly Imprinted Composites Initiated by Hemin/Graphene Hybrid Nanosheets and Its Application in Detection of Sulfamethoxazole.

Molecularly imprinted polymers (MIPs) exhibit high selectivity resulting from imprinted cavities and superior performance from functional materials, which have attracted much attention in many fields. However, the combination of MIPs film and functional materials is a great challenge. In this study, hemin/graphene hybrid nanosheets (H-GNs) were used to initiate the imprinted polymerization by catalyzing the generation of free radicals. Thus, MIPs using sulfamethoxazole as the template was directly prepared on the surface of H-GNs without any film modification. Most importantly, the template could be absorbed on the H-GNs to enhance the number of imprinted sites per unit surface area, which could improve the selectivity of MIPs film. Thus, the composites could exhibit high adsorption capacity (29.4 mg/g), imprinting factor (4.2) and excellent conductivity, which were modified on the surface of electrode for rapid, selective and sensitive detection of sulfamethoxazole in food and serum samples. The linear range was changed from 5 µg/kg to 1 mg/g and the limit of detection was 1.2 µg/kg. This sensor was free from interference caused by analogues of sulfamethoxazole, which provides a novel insight for the preparation of MIPs-based sensor and its application in food safety monitoring and human exposure study.