Quantification Bias in Blood Alcohol Determination by Headspace Gas Chromatography

Abstract

The quantification of blood alcohol concentration is routinely performed in many forensic laboratories by gas chromatography. In this short report, the influence of the matrix miss-match between samples and calibrators (e.g. the use of aqueous standards to quantify blood samples) and the actual efficiencies of different internal standards used to normalise the ethanol signal were considered. Test samples in blood and water were prepared from a certified reference standard of ethanol. The samples were analysed by gas chromatography using n-propanol and t-butanol as internal standards. The collected data provided evidences that a sub-optimal setting of the considered variables can be responsible for a quantification bias up to 15%. These issues are of practical relevance in the medico-legal sector and should be considered during the process of method development.