In Situ Generated Photolytic Silver in a Gelatin Matrix: An Approach for High-Throughput SERS Spectroscopy Applying Microtiter Plates

In order to develop a high-throughput analysis method based upon surface-enhanced Raman scattering (SERS) spectroscopy, we have successfully tested the possibility of generating SERS-active silver surfaces from home-made AgX dispersions deposited in the wells of commercially available microtiter plates. In an effort to reduce the number of preparation steps, the SERS-active silver metal surface is generated from the silver halides in situ after sample application by the tightly focused Raman probe laser. The intensity of the SERS signal increases initially with the conditions for a high-enhancement factor becoming optimal. Later on, it decreases as the solvent is evaporated completely. The signal can, however, be restored to a great extent by adding new refreshing solvent, preferably methanol. Pilot experiments using aromatic thiols and amines as test analytes proved that sample volumes as small as 1 mL with analyte concentrations down to 10⁻⁶ M are sufficient for recording of SERS spectra suitable to identify the analyte. A feasibility study was performed aimed at the identification of several analytes contained in the various fractions of the output of an analytical high-performance liquid chromatography (HPLC) instrument.