Coupling Single-Drop Microextraction with SERS: A Demonstration Using p-MBA on Gold Nanohole Array Substrate

Single-drop microextraction (SDME) was coupled with surface-enhanced Raman scattering (SERS) to provide sample extraction and pre-concentration for detection of analyte at low concentrations. A gold nanohole array substrate (AuNHAS), fabricated by interference lithography, was used as SERS substrate and para-mercaptobenzoic acid (p-MBA) was tested as a probe molecule, in the concentration range 10(-8)-10(-4) mol L-1. With this approach, a limit of 10(-7) mol L-1 was clearly detected. To improve the detection to lower p-MBA concentration, as 10(-8) mol L-1, the SDME technique was applied. The p-MBA Raman signature was detected in two performed extractions and its new concentration was determined to be similar to 4.6 x 10(-5) mol L-1. This work showed that coupling SDME with SERS allowed a rapid (5 min) and efficient pre-concentration (from 10 8 mol L-1 to 10(-5) mol L-1), detection, and quantification of the analyte of interest, proving to be an interesting analytical tool for SERS applications.