Correction of the alkylnitrite method for the measurement of ethanol in blood: direct experimental evidence

A coefficient (multiplier) for the correction of a systemic inaccuracy of ethanol detection in the blood by the alkylnitrite method arising from calibration against an aqueous solution has been improved. The experiment was carried out as a multilaboratory study (with the participation of six laboratories). The value of the coefficient was estimated at 0.82 +/- 0.014 (SD) instead of 0.95 computed earlier (CV = 1.7%). The main factor influencing the value of the coefficient turned out to be the time of preparation of the model ethanol-blood mixture for comparison with the aqueous solution. The coefficient of 0.82 was obtained using fresh blood samples that of 0.93 to 0.96 with blood samples previously stored during 3-10 days. The results of the study suggest different ethanol distribution patterns in vivo and in vitro in the aqueous phase of the blood stored for a few days.