Ethanol stability in unpreserved refrigerated antemortem blood.

Ethanol stability in preserved antemortem blood has been widely studied since it is a common practice in cases involving suspected impaired driving to collect antemortem blood in evacuated blood tubes containing sodium fluoride. In some situations, antemortem blood is submitted to a forensic laboratory for ethanol analysis in evacuated blood tubes that contain only an anticoagulant. There has been limited research on ethanol stability in antemortem blood stored without a preservative. On two occasions, antemortem blood was collected from five ethanol-free individuals into 6-ml Vacutainer® tubes containing only 10.8 mg potassium EDTA. The blood tubes were spiked with ethanol to approximately either 0.08 or 0.15 g/dl. Dual-FID headspace gas chromatography was used to analyze 58 blood tubes, 29 from each session, for ethanol 1 day after sample collection and again after 1 year of refrigerated storage (~4°C). Statistically significant decreases in ethanol were detected at the 0.05 level of significance. Mean decreases in ethanol after 1 year of storage for the 0.08 and 0.15 g/dl samples were 0.013 and 0.010 g/dl, respectively. The mean ethanol decrease across all tubes was 0.012 g/dl. The range of decreases for the 58 blood tubes was 0.003-0.018 g/dl. The mean ethanol decreases measured in this unpreserved antemortem blood are comparable in magnitude to those previously observed in antemortem blood containing sodium fluoride after 1 year of refrigerated storage. Ethanol did not increase in the antemortem blood samples despite the absence of sodium fluoride.

Large-scale reanalysis of refrigerated antemortem blood samples for ethanol content at random intervals.

Ethanol stability in antemortem blood stored under various conditions has been widely studied. Most such studies have somewhat limited sample size (<50) and limited variation in the length of time between the blood draw and the first analysis and between the first analysis and the reanalysis. In the work presented here, the antemortem blood drawn for forensic purposes and stored refrigerated (~4°C) in 371 cases was analyzed for ethanol concentration using headspace gas chromatography at various times after the blood draw based on routine case flow and then also analyzed at various times within approximately 1 year after the first analysis. This methodology is intended to provide insight into the range of differences expected when cases are analyzed in the normal flow of casework and then reanalyzed at random times afterwards as occurs when reanalysis is performed by the defense or by the laboratory if the original analyst is unavailable to testify. In 22 cases, the same blood tube from the case was reanalyzed. The previously unopened blood tube from the case was analyzed in 349 cases. The 25 cases in which the blood was ethanol-negative based on the first analysis remained ethanol-negative when reanalyzed. The average difference in ethanol concentration between tests for the ethanol-positive cases was -0.004 g/dL. This decrease was statistically significant at the 0.05 level of significance. The range of differences was -0.0197 to 0.0103 g/dL. The difference measured in 85% of the ethanol-positive cases was in in the range of -0.008 to -0.001 g/dL.

Isobutylene contamination of blood collected in 10-ml evacuated blood collection tubes with gray conventional rubber stoppers.

Dual-column headspace gas chromatographic analysis with two flame-ionization detectors is a commonly used analytical technique for forensic blood ethanol quantitation. This technique is also applicable to the identification and quantitation of other volatile organic compounds such as methanol in biological samples. Compound identification by retention time is limited to those compounds with known retention times programmed into the instrument method. Historically, an early-eluting peak from an unidentified compound has been observed in both chromatograms from antemortem blood samples analyzed for ethanol concentration with this technique. The unidentified compound's retention time matches that of methanol on one column but not on the second column. This previously unidentified compound has been identified as isobutylene. The proposed source of the isobutylene contamination historically observed in antemortem blood samples collected in 10-ml gray-top blood collection tubes is the conventional rubber stopper. Isobutylene was detected in deionized water stored in each of the seven lots of 10-ml blood tubes tested; the expiration dates of the tubes tested spanned the years 2002-2022. Misidentification of isobutylene as methanol is possible when using a single-column gas chromatographic system. The presence of isobutylene in blood collected in a gray-top collection tube does not represent laboratory contamination, is not an interferent with blood ethanol quantitation, and does not affect the ethanol concentration in the blood. A 0.150 g/dl aqueous ethanol standard was stored in a gray-top tube to evaluate the potential impact of isobutylene on ethanol quantitation. The solution's average ethanol concentration measured after storage was 0.150 g/dl.

The effect of sample hemolysis on blood ethanol analysis using headspace gas chromatography.

Hemolysis, a common occurrence in blood collected for chemical analysis, has been reported to affect analytical test results for some analytes depending upon the material tested and the analytical technique employed. The potential for hemolysis to impact blood ethanol determinations using headspace gas chromatography of samples diluted with an internal standard was investigated. A sample of non-hemolyzed blood and a matched sample of hemolyzed blood were both analyzed thirty times for ethanol concentration using headspace gas chromatography. The mean ethanol concentration measured for the non-hemolyzed samples was 0.0639 g/dl. The mean ethanol concentration measured for the hemolyzed samples was 0.0642 g/dl. The calculated t value, 1.897, was less than the critical t value, 2.002, at a 0.05 level of significance. There was no measured statistical difference detected between the mean blood ethanol concentration determined for a hemolyzed whole blood sample and a non-hemolyzed whole blood sample.