From relative to absolute quantification. To test whether the PCIS 2F-AEA enables endocannabinoid quantification using a calibration curve in neat solution, 12 aliquots of the lab plasma pool were prepared until dryness, reconstituted in 24 µL of injection solution and pooled. A plasma calibration curve was created mixing 20 µL of plasma pool with 20 µL of a CALsolution (CAL2 up to CAL8) and 10 µL of mixed working solution of deuterated standards. Also, a blank (non-spiked plasma) was included, wherein 0.4 mg/mL BHT in MeOH replaced the CAL-solution. Neat calibration standards were prepared similarly, only the plasma concentrate was replaced by injection solution. Samples were analyzed in duplicate using LC-MS/MS with 2F-AEA as a PCIS.