Modification of an Electrochemical Abacavir-Sulphate-Specific Sensor Using Molecular Imprinting for Enhanced Selectivity in Complex Sample Matrices

Abacavir sulphate residues reported in South African water resources highlight the need for monitoring pharmaceutical contaminants to assess wastewater treatment efficiency and protect aquatic ecosystems. This study aimed to determine whether combining molecularly imprinted polymers (MIPs) with a carbon paste electrode (CPE) could improve the selectivity and sensitivity of abacavir detection while providing a cost-effective alternative to conventional methods. The optimized MIP-CPE sensor was applied to determine abacavir sulphate in real water matrices. The MIP was attained by bulk polymerization and coupled with CPE. The MIP had thermal stability of greater than 300 °C. Using differential pulse voltammetry (DPV), it was possible to quantify abacavir sulphate using a redox probe; a linear response in a range of 2 to 14 µM with a correlation coefficient (R2) of 0.991 was observed, with lower limits of detection (LOD) and quantification (LOQ) of 1.47 µM and 4.47 µM, respectively. Thus, the developed MIP-CPE sensor can be used to detect analyte residues present at trace levels. The developed sensor demonstrated satisfactory accuracy and precision in real water matrices, achieving recoveries of 82.2–101.2% with RSD values of 1.27–7.34% for spiked abacavir sulphate concentrations of 8 and 12 µM. The presence of abacavir sulphate was only detected in uMhlathuzana wastewater effluent samples, with a concentration of 7.19 µM (RSD 7.40%, n = 3). The MIP-CPE showed high selectivity for abacavir sulphate when tested alongside common interferents (lamivudine, ibuprofen, nevirapine, and trimethoprim). Abacavir sulphate gave the lowest peak current (DPV) of the group (489 µA), due to the ferricyanide peak falling when the target rebinds and blocks the probe. A lower current for abacavir therefore means more rebinding, which is evidence of selectivity. The MIP-CPE sensor demonstrated rapid rebinding and strong affinity for abacavir sulphate, even in complex matrices. This study offers wastewater treatment plants as a cost-effective, sensitive, and selective analytical method for routine monitoring of antiretroviral contaminants before effluent discharge into environmental waters.