Evaluating the ability of PCIS to correct for differences in matrix effect. Three methods were applied to test the performance of 2F-AEA as a PCIS. For Method 1, 9 diverse plasma samples (numbered 1 to 9) and an aliquot of the lab plasma pool were prepared. They were reconstituted in 50 µL, consisting of 30 µL of injection solution, plus 5, 10 or 20 µL of mixed working solution of deuterated standards and 15, 10 or 0 µL of 0.4 mg/mL BHT in MeOH to prepare concentration levels at LOW (plasma 1, 2 and 3), MID (plasma 4, 5, 6 and the lab plasma pool) and HIGH (plasma 7, 8, 9) concentration, respectively. For each level, a neat (matrix-free) solution was prepared identically. Samples were analyzed in triplicate using the described LC-MS/MS method with 2F-AEA (150 ng/mL) as a PCIS.