Detection of rhodamine 6G in blood and urine using combination of surface-enhanced Raman spectroscopy and liquid-liquid extraction

The aim of this report is detection of model compound, rhodamine 6G (R6G), in blood and urine samples using surfaceenhanced Raman spectroscopy (SERS) as a detection tool and liquid-liquid extraction (LLE) for improving quality of SERS analysis (SERS-LLE combination). SERS substrate is a plasmonic nanomaterial which possesses drastic increasing of Raman spectrum intensity (10⁶‒10⁸) of any molecule adsorbed onto its surface. Here we used citrate stabilized silver nanoparticles as SERS substrate and synthesized them applying wet chemical approach. Before SERS measurements, blood and urine samples were artificially contaminated with R6G using 50 and 500 ng/mL concentrations for both samples. In order to reduce detectable concentrations of R6G and improve signal-to-noise ratio, we applied LLE which allows us to separate R6G from the matrix mixture and increase the analyte concentration. Four different LLE protocols were used and the most efficient one was found. Obtained results showed usefulness of SERS-LLE combination for chemical analysis of body fluids with level of detectable concentration down to tens ng/mL.