(a)
(b)
(c)
(d)
Figure 3: Commercially available internal standards for analysis by mass spectrometry. (a) Arachidonoyl ethanolamide-d4 (AEA-d4). (b) Arachidonoyl ethanolamide-d8 (AEA-d8). (c) 2-Arachidonoyl glycerol-d5 (2-AG-d5). (d) 2-Arachidonoyl glycerol-d8 (2-AG-d8).