A dilute–and–shoot LC–MS/MS determination of low–dosage third–generation antipsychotics and their metabolites in urine using an ultra-short column

Third–generation atypical antipsychotics, known for their enhanced efficacy and reduced side effects compared to previous generations, are now extensively utilized in the treatment of schizophrenia. Due to their chemical properties and low dosages, these drugs are present at low concentrations in urine, making it challenging to monitor medication compliance among probationers. In this study, a liquid chromatography-tandem mass spectrometric (LC–MS/MS) method was developed and validated for the determination of three third-generation antipsychotics and their main metabolites in urine. A dilute-and-shoot approach was employed for rapid urine sample preparation. All compounds were separated on an ultra-short column (2.1 × 5 mm, 1.7 μm) and detected rapidly within a span of two minutes, thereby enhancing the efficiency in handling increased workloads. The limits of detection ranged from 0.01 to 0.23 ng/mL for all compounds, with correlation coefficients exceeding 0.997. The analytical method was validated using various parameters, including selectivity, precision and accuracy, matrix effect, and stability, ensuring its reliability for forensic applications. This newly developed LC–MS/MS method was successfully applied to analyze 86 urine samples obtained from probationers undergoing antipsychotic medication. Consequently, this method proves to be useful in verifying medication compliance among probationers, and effectively managing the recent increase in the number of urine drug testing.