Laser-scribed graphene on polyetherimide substrate: an electrochemical sensor platform for forensic determination of xylazine in urine and beverage samples.

A laser-scribed graphene (LSG) device fabricated on polymeric polyetherimide (PEI) substrate is reported for sensitive electrochemical detection of xylazine (XLZ), a veterinary drug that has been associated with drug-facilitated crimes. Morphological characterization was made by scanning electron microscopy (SEM), demonstrating that the electrochemical device presents a highly porous carbonaceous structure. In addition, Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), wettability, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) measurements were used to characterize the PEI-LSG material, which showed superior electroanalytical performance after a simple anodic treatment in an alkaline medium (applying 2 V for 120 s in 0.1 mol L-1 NaOH solution). The electrochemical determination of XLZ was carried out using square wave voltammetry (SWV), which showed sensitivity and coefficient of determination (R2) equal to 0.206 ± 0.008 A L mol-1 cm-2 and 0.991, respectively. In addition, we obtained a low limit of detection (LOD) of 1.39 × 10-7 mol L-1 with a linear response in the concentration range 5.0 to 200.0 × 10-6 mol L-1. The PEI-LSG electrochemical sensor was applied to XLZ detection in commercial beverage and synthetic urine samples, providing recoveries between 96.0 and 114.8%. Collectively, our electrochemical sensor presents an easy method to manufacture reproducible (relative standard deviation (RSD) of 2.56%), low-cost ($0.12), and single-use (disposable) devices, which is a promising way for in-field determination of drug-facilitated sexual assaults and other relevant applications.