Simultaneous determination of 14 nitroimidazoles using thin-layer chromatography combined with surface-enhanced Raman spectroscopy (TLC-SERS)

Abstract

Nitroimidazoles are a family of veterinary drugs containing a 5-nitroimidazole ring structure, which are commonly used antibiotics. In view of their potential genotoxicity and possible coexistence in actual samples, it is necessary to establish a rapid and effective method for the simultaneous determination of multiple nitroimidazoles. In this study, a rapid thin-layer chromatography combined with surface-enhanced Raman spectroscopy (TLC-SER) detection method for 14 nitroimidazole compounds has been established. The theoretical Raman spectra of the nitroimidazoles were calculated using the B3LYP/6-311+G(d) basis set in density functional theory (DFT) and the theoretical Raman spectra of TNZ, NBZ, ONZ, SCZ, DMZ, MNI, 2-HMZ, 4-HMZ, CMNI, IPZ, MNZ-OH and HMDMZ have been obtained for the first time. SERS detection was carried out on a gold nanoparticles (AuNPs) substrate, which exhibited strong SERS signals and a limit of detection limit of 0.1 mg/L. By optimizing the conditions used for the developing agent in TLC, 12 nitroimidazoles were successfully separated, while MNZ and RNZ still could not be separated. When combined with the chemometrics analysis method, the TLC-SERS method can realize the simultaneous detection of 14 nitroimidazoles. Actual pork samples were spiked with nitroimidazoles with a recovery rate of 80%–110% and RSD of 0.74%–16.70%, which showed that SERS and TLC-SERS methods are also effective for detection in actual samples. The detection time of this method is < 10 min, which is suitable for the rapid detection of nitroimidazoles, especially for the rapid qualitative identification of nitroimidazoles in situ.