Ultra-sensitive method for determination of ethanol in whole blood by headspace capillary gas chromatography with cryogenic oven trapping

We have established an ultra-sensitive method for determination of ethanol in whole blood by headspace capillary gas chromatography (GC) with cryogeni c oven trapping. After heating a blood sample containing ethanol and isobut yl alcohol (internal standard, IS) in a 7.0-ml vial at 55 degrees C for 15 min, 5 mi of the headspace vapor was drawn into a glass syringe and injecte d into a GC port. All vapor was introduced into an Rtx-BAC2 wide-bore capil lary column in the splitless mode at -60 degrees C oven temperature to trap entire analytes, and then the oven temperature was programmed up to 240 de grees C for GC measurements with flame ionization detection. The present me thod gave sharp peaks of ethanol and IS, and low background noise for whole blood samples. The mean partition into the gaseous phase for ethanol and I S was 3.06+/-0.733 and 8.33+/-2.19%, respectively. The calibration curves s howed linearity in the range 0.02-5.0 mu g/ml whole blood. The detection li mit was estimated to be 0.01 mu g/ml. The coefficients of intra-day and int er-day variation for spiked ethanol were 8.72 and 9.47%, respectively. Beca use of the extremely high sensitivity, we could measure low levels of endog enous ethanol in whole blood of subjects without drinking. The concentratio n of endogenous ethanol measured for 10 subjects under uncontrolled conditi ons varied from 0 to 0.377 mu g/ml (mean, 0.180 mu g/ml). Data on the diurn al changes of endogenous ethanol in whole blood of five subjects under stri ct food control are also presented; they are in accordance with the idea th at endogenous blood ethanol is of enteric bacterial origin. (C) 1999 Elsevi er Science B.V. All rights reserved.