Evaluation of a solid-phase extraction membrane as a surface-enhanced Raman substrate

A commercially available solid-phase extraction membrane was evaluated as a substrate suitable for routine analysis by surface-enhanced Raman spectrometry (SERS). The material was silver coated in-house via chemical reduction. Because the material has chromatographic capabilities, the use of SERS as a detection method for thin-layer chromatography (TLC) was considered by separating, then detecting, a mixture of commonly used sulfonamides from the bare and coated material. While the mobilities of the sulfa drugs were not strongly affected by the silver, the SER response was weak anal analyte degradation was apparent. Some signal improvement was gained by dampening the surface with water in a simple surface modification. General substrate performance in both dry and in the modified dampened states was evaluated by using the model, crystal violet. The resulting analytical curves were linear across 1-2.5 orders of magnitude with limits of detection in the subnanogram range (total analyte applied). Under routine preparation and analysis procedures, reproducibility was <30%, but improvement to similar to 10% was possible when great care was used. Typical spectra for two compound series having a variety of functional groups were obtained and showed general trends for response dependence on functional group.