Extraction of the blood samples. 300 µl of plasma or RBC was used for each extraction. Initial samples were extracted as described by Raftery et al. A 1:2:2 ratio of chilled (4 ⁰C) plasma or RBC/methanol/chloroform mixture was used for the extraction. Samples were vortexed for a few seconds, until completely mixed and protein precipitate was visible. Next, the samples were then sonicated at 4 ⁰C for 2 minutes and kept at -20 ⁰C for 20 minutes. After centrifugation at 13 400 rcf for 30 minutes, the clear biphasic aqueous/methanol/chloroform solution was transferred to a new centrifuge tube. Most of the organic solvent was removed by a stream of N2 gas, and sample drying was completed by lyophilization overnight. The dried samples were stored at -80 ⁰C until analysis.