Development and optimization of a sensitive and specific colourimetric method for ketamine drug screening

Ketamine, a schedule 8 controlled substance in Australia, has increased in popularity alongside the emergence of ketamine-type new psychoactive substances (NPS), creating challenges for law-enforcement and harm minimization organizations in its rapid identification. This study describes the development, optimization and validation of a colourimetric reagent for the in-situ detection of ketamine HCl, based on the highly specific Morris reagent. Optimization included the introduction of an organic solvent to improve specificity, adjustment of reagent component ratios, and a simplification of the testing procedure. The resulting Morris 2.0 reagent achieved a 16-fold increase in sensitivity compared with the original Morris reagent while maintaining excellent specificity and selectivity. Among 107 non-ketamine compounds tested, only 3% produced false-positive results. Morris 2.0 successfully detected ketamine HCl and its metabolite norketamine HCl through a distinct purple colour change across a range of solid matrix concentrations. The reagent also demonstrated stability under extreme temperature fluctuations and generated reproducible results across multiple operators. The adoption of the Morris 2.0 reagent outlined in this paper by law-enforcement and harm-minimization organizations in crime-scene and pill testing scenarios would therefore be advantageous, owing to its simple, reliable, robust, sensitive and specific nature.