Highly reproducible SERS detection in sequential injection analysis: Real time preparation and application of photo-​reduced silver substrate in a moving flow-​cell

Abstract

This paper reports an improved way for performing highly reproducible surface enhanced Raman scattering of different analytes using an automated flow system. The method uses a confocal Raman microscope to prep. SERS active silver spots on the window of a flow cell by photo-redn. of silver nitrate in the presence of citrate. Placement of the flow cell on an automated x and y stages of the Raman microscope allows to prep. a fresh spot for every new measurement. This procedure thus efficiently avoids any carry over effects which might result from adsorption of the analyte on the SERS active material and enables highly reproducible SERS measurements. For reproducible liq. handling the used sequential injection anal. system as well as the Raman microscope was operated by the flexible LabVIEW based software ATLAS developed in the authors' group. Quant. aspects were studied using Cu(PAR)2 as a model analyte. Concn. down to 5 × 10-6 M provided clear SERS spectra, a linear concn. dependence of the SERS intensities at 1333 cm-1 was obtained from 5 × 10-5 to 1 × 10-3 with a correlation coeff. r = 0.999. The coeff. of variation of the method Vxo is 5.6% and the calcd. limit of detection 1.7 × 10-5 M. The results demonstrate the potential of SERS spectroscopy to be used as a mol. specific detector in aq. flow systems.