Electrochemical detection of Methadone by use of poly-l- arginine/carbon nanotubes composite modified carbon paste electrode (P-L-Arg/CNTs/CPE) in human urine

The current study focused on the easy synthesis of poly-l-arginine and carbon nanotubes composite on carbon paste electrode (P-L-Arg/CNTs/CPE) based on electropolymerization technique as wide range electrochemical sensor for determination of methadone in biological samples for doping monitoring between athletes. Structural analyses using SEM and XRD indicated that the p-L-Arg/CNTs/CPE surface had been covered with a homogenous structure of rod-like snowflakes. The nano-sized twisted bundled CNTs network with excellent surface area served as nucleation sites for the electropolymerization of L-Arg monomers. Study of electrochemical response of P-L-Arg/CNTs/CPE using CV and amperometery techniques illustrated considerable improvement of sensitivity and selectivity of P-L-Arg/CNTs/CPE due to synergistic effect of P-L-Arg and CNTs. Results showed that linear response was from 0 to 600 μM with a correlation coefficient of 0.99990, and the sensitivity and limit of detection of P-L-Arg/CNTs/CPE were obtained to be 0.02961 μA/μM and 22 nM, respectively. The comparison between the obtained sensing parameter of P-L-Arg/CNTs/CPE was compared with the other reported methadone sensors in the litereture revealing the broad linear range to the determination of methadone and an appropriate limit of the detection value of P-L-Arg/CNTs/CPE toward the other reported methadone sensors. The P-L-Arg/CNTs/CPE as a proposed sensing system for analysis of methadone in real samples prepared from the urine of four athletes was evaluated. Results exhibited that the RSD values (3.56% to 4.41%) and recovery (98.86% to 99.91%) satisfied appropriate validity and promising potential of the proposed sensor in the practical sample analysis.