Evaluation of Two Commercially Available TLC Materials as SER Substrates

Abstract

Two commercially available thin-layer chromatographic plates were evaluated as substrates for routine analysis by surface-enhanced Raman spectrometry (SERS). One plate was purchased precoated with silver; the other was coated in-house via chemical reduction. The use of SERS as a detection method for thin-layer chromatography (TLC) was also considered. To this end, a mixture of commonly used sulfonamides was separated and detected directly from each plate. The mobilities of the sulfa drugs were not strongly affected by the silver, but Raman response was weak and analyte degradation was apparent. Improvement was found through modification of the surface by adding a thin film of water to the substrate. Overall substrate performance was evaluated with the use of crystal violet as the model analyte in both dry and dampened states. Signal vs. concentration curves were linear across at least two orders of magnitude with limits of detection in the low- to sub-ng range (total analyte applied). Under routine preparation and analysis procedures, reproducibility was generally <30%, but improved to ∼10% when greater care was applied. Typical spectra for two compound series having a variety of functional groups were obtained, showing the substrates to be moderately active.