Ethanol levels in plasma, serum, and whole blood by time of collection. Plasma was obtained by centrifuging the samples immediately after collection for 15 min and pipetting the supernate. Serum was obtained by allowing the sample to sit for 45 min (allowing the sample to clot) before centrifuging and pipetting the supernate. Whole blood samples were not centrifuged before pipetting into analysis tubes. ASAP samples were analyzed as soon as possible on study day (within 6 h of collection); RT, 24 h samples were stored at room temperature (25°C) for 24 h and then analyzed; RT, 10 days samples were stored at room temperature (25°C) for 10 days and then analyzed; and 4°C, 10 days samples were refrigerated for 10 days and then analyzed. All samples at the −60 min time point were negative for ethanol. Values are means (± sem). Values for the 10 day samples were slightly lower, but not significantly different than ASAP or 24 h samples for plasma, serum, and whole blood.