Detection of synthetic cathinones in seized drugs using surface-enhanced Raman spectroscopy (SERS)

Abstract

There is need for a screening method to assist authorities in detecting cathinone analogs in a rapid, reliable, and sensitive fashion. This work describes the development of Ag colloidal systems for use as SERS-enhancing substrates to detect six synthetic cathinone analogs. Furthermore, specific interactions between the analyte and metal surface were probed by determining the effect of functional groups attached to the core synthetic cathinone. Initial work involved Density Functional Theory (DFT) calculations at B3LYP/6-311G** level to predict Raman frequencies of the studied compounds. Normal Raman measurements on dried solid residues of synthetic cathinone standards were next examined, and the resulting scaled spectra were used to ensure concordance of the DFT-predicted frequencies with experimental values. Subsequent work focused on the development of a SERS protocol, which included the selection of nanoparticles in solution, followed by the addition of aggregating agents such as MgCl₂ and KBr to produce high-density hot-spots on the nanometallic surface. Sample treatment conditions necessary to detect the selected synthetic cathinone analogs were also optimized. Once completed, the characterization and identification of the main peaks that make up the synthetic cathinone core structure were assigned and unique functional groups for each of the analogs were identified. Overall, the analytical process takes less than a minute, making the procedure useful for field screening. Ultimately, this procedure can aid law enforcement and first responders by providing a more specific method for rapid and sensitive on-site analysis of seized drugs.