Matrix-Tolerant Quantification of THC and THCA in Complex Cannabis Products Using In-Sample Calibration with Multiple Isotopologue Reaction Monitoring

> 0.999), precision (<10% RSD), and accuracy (±10%) in commercial CBD oils, gummies, creams, waxes, dietary supplements, and plant materials. Comparison with external calibration showed strong agreement across all matrices. Collectively, this work develops the ISCC-MIRM framework for heterogeneous consumer and forensic samples and establishes a practical, matrix-tolerant calibration strategy for routine cannabinoid analysis.