Individual stock solutions of each deuterated endocannabinoid were made in ACN at 0.10 mM, only for 2AG-d8 at 0.26 mM. A mixed stock solution of deuterated standards was prepared by mixing the right volumes of each individual stock and diluting with ACN to concentrations of 6.25 µM for all deuterated analytes, except for d8-NADA which had a concentration of 0.625 µM. This stock mix was further diluted with 0.4 mg/mL BHT in MeOH to a mixed working solution with concentrations of 0.188 µM (and 10 times lower for d8-NADA).