Rapid detection of illegal biguanides in hypoglycemic health products using molecular imprinting combined with SERS technology

In this work, the advantages of surface-enhanced Raman spectroscopy (SERS) sensitivity and molecularly imprinted technology selectivity were combined to achieve simultaneous detection of two biguanides, metformin hydrochloride (Met HCl) and phenformin hydrochloride (Phen HCl), in hypoglycemic health products. For this purpose, initially, gold nanoparticles (AuNPs) and graphene oxide (GO) were prepared. Subsequently, AuNPs were immobilized on GO through p-aminothiophenol to form the Au–GO composite. Finally, the molecularly imprinted polymer (MIP) was successfully prepared using Met HCl as the template molecule and coated onto the surface of the Au–GO composite to obtain the sandwich-structure substrate, [email protected]–GO. Static and kinetic adsorption studies demonstrated the specific recognition of [email protected]–GO for Met HCl and Phen HCl and a rapid adsorption equilibration rate. By simply incubating analytes with the [email protected]–GO substrate, the proposed method showed strong SERS signal enhancement with a limit of detection of 0.10 mg/mL (S/N = 3) for both Met HCl and Phen HCl. The substrate also exhibited excellent reusability and long-term stability. Moreover, the method was successfully applied to the quantitative detection of Met HCl and Phen HCl in real hypoglycemic health products with satisfactory recoveries and standard deviations. The recoveries of Met HCl by [email protected]–GO ranged from 87.5% to 112.5% with relative standard deviations (RSDs) of 0.8%–8.9%. The recoveries of Phen HCl ranged from 96.7% to 115% with RSDs of 3.1%–7.4%. The detection time is only 10 min. Overall, the novel approach appeared to be simple, rapid, and highly specific, thus could be effective for the on-site screening and detection of chemical drugs in complex matrices.