A fast response TLC-SERS substrate for on-site detection of hydrophilic and hydrophobic adulterants in botanical dietary supplements
Thin layer chromatography coupled with surface enhanced Raman spectroscopy (TLC-SERS) has received great development but still suffers from the problem of detecting hydrophobic analytes. A relatively universal silver colloid, which is applicable for both hydrophilic and hydrophobic analytes, has been synthesized to solve this problem. However, it is difficult to obtain a fast response for reaching the maximum SERS intensity. Herein, we further optimized the preparation process of the above universal silver colloid, namely silver nanoparticles synthesized in N,N-dimethylformamide (AgNPs-DMF), and studied their surface enhanced Raman spectroscopy (SERS) performance on TLC plates. Here, the SERS performance of the silver colloids prepared with different mass ratios (AgNO3/PVP, m/m) was compared and we found that DMF 2 : 1 silver colloid gave the largest enhancement ability. In addition, it was also found that DMF 2 : 1 silver colloid could be stored for 90 days without significant intensity attenuation. Moreover, practical application of this novel DMF 2 : 1 colloid combined with the TLC-SERS method to analyze real botanical dietary supplement (BDS) samples claiming to have lipid-lowering or antitussive and antiasthmatic effects was successfully carried out. Results showed that the application of this newly synthesized fast response and highly stable non-aqueous sol using the TLC-SERS technique would have bright prospects for the rapid detection of large amounts of samples on site.