Liquid chromatography with electrochemical detection for the determination of choline and acetylcholine in plasma and red blood cells. Failure to detect acetylcholine in blood of humans and mice.

An assay is described for the measurement of choline in plasma and red blood cells using liquid chromatography, an enzyme reactor and electrochemical detection after a simple sample pretreatment. The intra-assay coefficient of variation for choline was 6.2 and 3.8% in plasma and in red blood cells, respectively. Using this method we have re-investigated the presence of acetylcholine in blood constituents. We were not able to demonstrate acetylcholine with a limit of detection of 10 pmol per ml of plasma or per ml of red blood cells.