Background: Determination of heroin in urine is challenging because of matrix interference and heroin instability; therefore, this study aimed to develop a selective molecularly imprinted polymer-based solid-phase extraction method coupled with UV–Vis spectrophotometry for heroin determination in urine.
Methods: Heroin-imprinted polymers were synthesized by precipitation polymerization using benzoyl peroxide (BPO) as initiator, ethylene glycol dimethacrylate (EGDMA) as crosslinker, and either N-hydroxyethyl acrylamide (HEAA) or 3-(trimethoxysilyl)propyl methacrylate (TMSPMA) as functional monomers. Template removal was performed by Soxhlet extraction. Polymer formation and template removal were evaluated using FT-IR spectroscopy. MIP particles were packed into syringe SPE cartridges and applied to heroin-spiked urine samples (40–80 ppm). Heroin was quantified by UV–Vis spectrophotometry at 230 nm after MISPE clean-up and reconstitution in ethanol, using a global calibration curve (20–100 ppm).
Results: The UV–Vis calibration curve was linear across 20–100 ppm (A = 0.0146C − 0.0607; R2 = 0.9999). In urine matrix experiments (n = 3 replicates per level), recoveries ranged from 97.0% to 102.75%, with repeatability RSD = 1.24–3.83%. The global limit of detection was 0.010 ppm.
Conclusion: MISPE using heroin-imprinted polymers coupled with UV–Vis at 230 nm is a practical approach for determining heroin in spiked urine with acceptable within-run performance; however, expanded validation (selectivity and stability testing) is recommended for forensic-defensible application.