Table 1. . Overview of current methods for measuring anandamide and 2-arachidonoyl glycerol.

Species	Biological sample	Purpose of study	Sample preparation and analysis	Analytical figures for AEA and 2-AG respectively	Ref.
Human	Plasma	Quantitation of ECs, prostanoids and steroids	Solid-phase extraction; LC–MS/MS	LOQ 0.1 ng/ml; 3.2 ng/ml	[16]
Rat	Tissues	Quantitation of ECs, ceramides and oxysterols	Solid-phase extraction; LC–MS	LOQ 1.7 pmol; 2.5 pmol (on column)	[17]
Black bear	Serum	Quantitation of 5 ECs in serum	Liquid–liquid extraction; microflow LC–MS/MS	LOQ 1.7 pg/ml; 13.4 pg/l	[18]
Human	Plasma	Quantitation of ECs	Liquid–liquid extraction; LC–MS/MS	LOQ 0.5 nM (AEA only)	[19]
Human	Plasma	Quantitation of AEA and ethanol amides	Liquid–liquid extraction; GC–MS/MS	LOQ 0.25 nM (AEA only)	[21]
Human	Serum	Quantitation of 14 ECs in serum	Solid-phase extraction; LC–MS/MS	LOQ at pg/ml level for all 14 ECs	[23]
Rat	Hypothalamus	Regulation of EC release by CB1 receptors	MD, microSPE; LC–MS/MS	LOQ 30 amol; 300 amol (on column)	[24]

2-AG: 2-arachidonoyl glycerol; AEA: Anandamide; CB: Cannabinoid; EC: Endocannabinoid; LOQ: Limit of quantitation; MD: Microdialysis; SPE: Solid phase extraction.