In situ enrichment and determination of 6 kinds of caine-type anesthetics in cosmetics and rat serum by thin layer chromatography-Raman spectroscopy

A simple, economical and selective method has been established for simultaneous detection of 6 kinds of caine-type anesthetics in cosmetics and rat serum by in situ enrichment thin layer chromatography (TLC) and Raman spectroscopy. The target caine-type anesthetics, procaine hydrochloride (Pro), tetracaine hydrochloride (Tet), dibucaine (Dib), mepivacaine hydrochloride (Mep), lidocaine hydrochloride (Lid) and ropivacaine hydrochloride (Rop), were separated by TLC. The original spots (or position of Rf equal to that of the standard) of anesthetics on TLC plates were in situ enriched into much smaller ones driven by solvent from different directions, and followed by Raman measurement for quanlitative and quantitative analysis, resulting in the improvement of sensitivity and selectivity. Optimization and standardization of the experimental conditions, the composition and proportion of developing solvent, were conducted. Thus a robust and reliable approach which enabled effective separation, accurate identification and quantification has been developed with the lowest detectable amounts of 0.4, 0.2, 1.2, 1, 1 and 1 μg for Pro, Tet, Dib, Mep, Lid and Rop, respectively. The established method was successfully applied in anesthetics analysis in cosmetics (essence, cream and gel) and rat serum without complex sample pretreatment processes, and the results were verified by HPLC. It turned out that the in situ enrichment TLC-Raman technique was feasible and effective for separation and determination of 6 caine-type anesthetics in biological samples and cosmetics, and would have good prospects for on-site qualitative screening of prohibited goods and adulterants.