Gold nanorods as SERS substrate for the ultratrace detection of cocaine in non-pretreated oral fluid samples

Publication date: Available online 26 May 2018Source: Colloids and Surfaces A: Physicochemical and Engineering AspectsAuthor(s): Valentina D’Elia, Jorge Rubio-Retama, Fernando E. Ortega-Ojeda, Carmen García-Ruiz, Gemma MontalvoAbstractThis work shows the capability of surface-enhanced Raman spectroscopy (SERS) to detect ultratraces of cocaine (COC) in oral fluid (OF). It proposes a new solid substrate made of gold nanorods (Au NRs) to perform sensitive analyses of this complex matrix without any sample pretreatment. The Au NRs were synthetized optimizing the synthesis conditions, and then characterized and tested as SERS substrate. The presented results demonstrated that the SERS methodology was able to detect COC in OF with a limit of detection (LOD) as low as 10 ng/mL. This value was five orders of magnitude smaller than the one obtained with Raman spectroscopy (RS) and in the order of the cut-off value (8 ng/mL) established for confirmatory test of COC in OF. Besides, a multivariate analysis (OPLS-DA) applied on the samples analysed by SERS evidenced that it was possible to discriminate among various COC concentrations. These are quite positive results because even the 1 ng/mL COC concentration sample could be identified as different from the OF sample. In addition, the absence of sample pretreatment and the ease of the proposed method, allowed performing rapid and non-destructive analyses, making the method suitable for in situ forensic analyses.Graphical abstrac...
Source: Colloids and Surfaces A: Physicochemical and Engineering Aspects - Category: Chemistry Source Type: research