Surface-enhanced Raman Spectroscopy as a Technique for Drug Analysis

Abstract

In situ surface-enhanced FT-Raman (SERS) detection of heroin, codeine and cocaine samples after separation on a Kieselgel 60 type Chromatographie thin layer has been performed. With a silver coating applied onto the TLC spots by vacuum evaporation a detection Iimit of about 0.2 ~g/mm 2 could be attained. Due to the low matrix effect of the silicate-based stationary phase, SERS detec-lion of drugs cau be used as a quick and reliable identification method. Separation methods based solely on relative retention and traditional detection techniques often face the problern of similar Chromatographie behaviour. As a consequence, attention has been paid to the application of so-called hyphenated techniques. Recently attempts have been successfully made for the in situ detection of thin layer Chromatographie spots by the FT-IR [ 1-3] and surface-enhanced Raman spectroscopic (SERS) techniques [ 4-7]. According to our experience [8] FT-IR analysis of TLC spots of real drugs can be done quickly and reliably in spite of the fact that the matrix effect of the Chromato-graphie stationary phase often spoils qualitative analysis. In our judgement, surface-enhanced Raman spectroscopic detection after chromatographic Separation offers reliable analysis where the eluent and/or Chromatographie stationary phase will give a strong matrix effect. In spite of the fact that the use of FT-Raman spec-troscopy in TLC analysis is rather limited, owing to the spectral properties of the analyte and to the relatively high amount of sample, the in situ SERS analysis ofthe TLC spots of heroin, codeine and cocaine can be done with certainty.