Optimizing Cannabis Sample Preparation to Reduce Chloroform Usage: A Comparison of I-Optimal, D-Optimal, and A-Optimal Designs

The aim of this study was to identify a safer solvent system to reduce toxic chloroform usage, consisting of a mixture of acetonitrile, methanol, and water, for the preparation of cannabis samples. A comparison among I-optimal, D-optimal, and A-optimal experimental designs for Charlotte's Angel and Hang Kra Rog Phu Phan cultivars was conducted. Results indicated that the I-optimal and D-optimal designs exhibited similar contour plot patterns and design spaces, which differed from those of the A-optimal design. The optimal solvent mixture that maximized both cannabidiol and ∆⁹-tetrahydrocannabinol for both cultivars was acetonitrile:methanol:water in the ratio 0.571:0.0890:0.340, demonstrating that this safer mixture performed comparably to the standard methanol:chloroform (9:1) system. The cannabidiol and ∆⁹-tetrahydrocannabinol contents extracted using the optimal mixture were not significantly different from those obtained with the chloroform-containing system, confirming its effectiveness. Furthermore, during a 28-day study period, cannabidiol and ∆⁹-tetrahydrocannabinol stored at 4 and -20°C remained stable, with no significant differences observed. In conclusion, the I-optimal design effectively optimized the cannabis sample preparation using a safer solvent mixture, reducing chloroform usage while maintaining comparable extraction efficiency and stable cannabinoid content.