Rapid Qualitative and Quantitative Detection of 3 Illegally Added Anti Infective Drugs by Nanogold Surface-Enhanced Raman Spectroscopy

Using the nanogold sol prepared by the sol-gel method as the substrate, the qualitative and quantitative study of 3 illegally added anti infective drugs including metronidazole, enoxacin and fluconazole, was carried out by surface-enhanced Raman spectroscopy (SERS). An aliquot (950 μL) of 1% (mass fraction) chloroauric acid solution was taken and mixed with 60 mL of water, and the mixture was vigorously stirred at 100℃ until the solution boiled, and 0.6 mL of 1% (mass fraction) sodium citrate solution was added. The above mixed solution was settled for 20 min until the solution color turned purple red, and cooled to room temperature. The resulting nanogold sol was stored at 4℃. The standard solution (50 μL) was taken, and 450 μL of nanogold sol was added. The mixture was detected within 100-3 000 cm^-1 using Raman spectrometer. It was shown that the qualitative Raman characteristic peaks of the 3 anti infective drugs were 1 180, 1 264, 1 364, 1 550 cm^-1 for metronidazole, 1 346, 1 424 cm^-1 for enoxacin and 986, 1 370 cm^-1 for fluconazole, respectively, with the quantitative Raman characteristic peaks of 1 364 cm^-1 for metronidazole, 1 424 cm^-1 for enoxacin and 982 cm^-1 for fluconazole. The linear relationships between values of the mass fraction and the peak area of the quantitative Raman characteristic peak of the 3 anti infective drugs were found in the ranges of 0.500-10.000 mg·kg^-1 (metronidazole) and 2.000-20.000 mg·kg^-1 (enoxacin and fluconazole), with detection limits (3.143s) in the range of 0.12-0.39 mg·kg^-1, recoveries in the range of 88.5%-108%, and RSDs (n=7) of the determined values in the range of 1.9%-5.3%.