Computer-Aided Headspace Gas Chromatography Applied to Blood-Alcohol Analysis: Importance of Online Process Control

Abstract

This paper describes the analysis of ethanol in blood specimens from suspect drunk drivers and the associated quality assurance procedures currently used in Sweden for legal purposes. Aliquots of whole blood from two separate Vacutainer® tubes are diluted with 1-propanol as internal standard before analysis by headspace gas chromatography (HS-GC) with three different stationary phases: Carbopak B, Carbopak C, and 15% Carbowax 20 M. The actual HS-GC analysis, the integration of chromatographic peaks, the collection and processing of results, as well as the quality control tests involve the use of computer-aided techniques. The standard deviation of analysis (y) increased with concentration of ethanol in the blood specimen (x), and above 0.50 mg/g the regression equation was y = 0.0033 + 0.0153x. The prosecution blood-alcohol concentration (BAC) is the mean of three separate determinations made by different laboratory technicians working independently with different sets of equipment. A deduction is made from the mean analytical result to compensate for random and systematic errors inherent in the method. At BACs of 0.5 and 1.5 mg/g, which are the statutory limits in Sweden, the allowances currently made are 0.06 and 0.09 mg/g, respectively. Accordingly, the reduced prosecution BAC is less than the actual BAC with a statistical confidence of 99.9%.

Comparison of ethanol concentrations in venous blood and end-expired breath during a controlled drinking study

“…At a mean ethanol concentration of 0.8 mg/g, the S.D. was 0.006 mg/g, which corresponds to a coefficient of variation of 0.75% indicating high analytical precision [16]. The limit of quantitation of blood-ethanol concentration in this research study was 0.01 mg/g.…”

Influence of CYP2D6 genotype on the disposition of the enantiomers of venlafaxine and its major metabolites in postmortem femoral blood

“…Ethanol was determined in blood by head-space GC according to a previously described method [36]. Urine and/or blood samples were also analyzed for different classes of illicit drugs (opiates, cannabis, amphetamines, cocaine and gamma-hydroxybutyrate) after a direct request by the responsible forensic pathologist.…”

Determination of Volatile Substances in Forensic Samples by Static Headspace Gas Chromatography

“…There are several columns for alcohol separation available on the market, that can be used for the chromatographic separation, but if it is necessary to determine non-polar volatile substances, it is advisable to choose a column that allows separating all the analytes of interest in a reasonable time; subsequent analyses in two or three chromatographic systems can be performed in order to confirm the obtained results, each one with different retention times for ethanol and internal standard; in some cases, it is even possible to perform a confirmation test with a different internal standard (Brown & Long, 1988;Jones & Schuberth, 1989), finally, FID is the chromatographic detector more commonly used for this kind of analyses. The chromatographic conditions most commonly used for the analysis of ethanol in biological samples are summarized in table 2.…”

“…The accuracy and reproducibility of the analysis performed in such a way is high, resulting in inter-laboratory coefficients of variation (CV) of 3% to 5%, and intra-laboratory CV of less than 1%, both with adequate sensitivity (LOD around 1 mg/dl) and high specificity (Jones & Schuberth, 1989;Jones, et al, 1992;Penton, 1985).…”