Aminopyrine Raman spectral features characterised by experimental and theoretical methods: toward rapid SERS detection of synthetic antipyretic-analgesic drug in traditional Chinese medicine

The adulteration of traditional Chinese medicine (TCM) with synthetic drugs severely harms the TCM effect and public health. Thus, quick detection of synthetic drug found in TCM is crucial. Here, we report surface-enhanced Raman scattering (SERS) coupled with density functional theory (DFT) calculations for the direct identification and detection of aminopyrine (AP) in TCM using silver-coated gold nanoparticles (Au@Ag NPs). It has been demonstrated that the Raman enhancement of Au@Ag NPs to AP was stronger than that of Au, Ag and Ag@Au NPs, and there was a strong dependence of the Raman enhancement on the substrate concentration. Moreover, we obtained the DFT calculation result of AP and found that the calculation result was in good agreement with the experimental one. In addition, the characteristic peak at 999 cm(-1), which was the strongest peak in the SERS spectra, was used for a quantitative evaluation of the AP level. The limit of detection (LOD) was 2.50 x 10(-7) M (equal to 57.8 ng mL(-1)) in aqueous solution, which was in the same order of magnitude as that obtained by liquid chromatography-mass spectrometry (LC-MS), and the recovery of AP ranged from 93.9% to 101% in the spiked TCM (Shexiang Fengshi capsule) sample. Each test using the SERS sensor only needed a 10 mu L sample solution and the whole test could be accomplished within similar to 3 min. The SERS technique can be applied to authenticate and detect trace AP in real herbal products.