EVALUATION OF 2 COMMERCIALLY AVAILABLE TLC MATERIALS AS SER SUBSTRATES

Two commercially available thin-layer chromatographic plates were eval uated as substrates for routine analysis by surface-enhanced Raman spe ctrometry (SERS). One plate was purchased precoated with silver; the o ther was coated in-house via chemical reduction. The use of SERS as a detection method for thin-layer chromatography (TLC) was also consider ed. To this end, a mixture of commonly used sulfonamides was separated and detected directly from each plate. The mobilities of the sulfa dr ugs were not strongly affected by the silver, but Raman response was w eak and analyte degradation was apparent. Improvement was found throug h modification of the surface by adding a thin film of water to the su bstrate. Overall substrate performance was evaluated with the use of c rystal violet as the model analyte in both dry and dampened states. Si gnal vs. concentration curves were linear across at least two orders o f magnitude with limits of detection in the low- to sub-ng range (tota l analyte applied). Under routine preparation and analysis procedures, reproducibility was generally <30%, but improved to similar to 10% wh en greater care was applied. Typical spectra for two compound series h aving a variety of functional groups were obtained, showing the substr ates to be moderately active.