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 ~4.6 × 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.