Rapid detection of illegally added nifedipine in Chinese traditional patent medicine by surface-enhanced Raman spectroscopy.

Nifedipine is an antihypertensive chemical. The illegal addition of this chemical into Chinese traditional patent medicine (CTPM) is unstandardized and lacks regulation. It could bring serious side effects to patients, causing various symptoms. Therefore, accurate detection of nifedipine is very important for human health and the prevention of illegal additives. Surface-enhanced Raman spectroscopy (SERS) is a fast and sensitive fingerprint spectroscopic technique, which has been shown to be promising in drug detection. In this study, nifedipine in CTPM was determined qualitatively and quantitatively with SERS. Linear relationships between the concentrations of nifedipine and the intensities of the characteristic peaks were established. The results showed a linear relationship within the concentration range of 0.5-10 mg/L, and the lowest detectable concentration of nifedipine in CTPM was 0.1 mg/L (equivalent to 0.03% doping of nifedipine in CTPM). This method has shown a great potential in the detection of drugs illegally added to CTPM.