Determination of Ethanol in Blood: Analytical Aspects, Quality Control, and Theoretical Calculations for Forensic Applications

Abstract

According to current Swiss traffic law, a person with 0.8 g/kg or more of alcohol in the blood is not permitted to drive. Given special circumstances, driving under the influence of alcohol can be diagnosed even with less than 0.8 g/kg. The Federal Department of Justice and Police defines how the analysis of blood samples taken from road traffic participants has to take place. The Swiss Federal Roads Authority is responsible for the implementation of these regulations. Other measurements of blood alcohol with a forensic background are done in the same way. Each blood sample must be tested fourfold, twice with one method, twice with another. The enzymatic method (ADH) and gas chromatographic methods (GC) are currently certified for this. It is possible to adopt new methods once they receive scientific recognition. Procedures using GC columns with a clearly distinct separation behavior and distinct internal standards are considered as separate methods. As an injection procedure, the headspace technique has gained general acceptance, while the flame ionization detector (FID) is used for detection. With respect to the homogeneity of the four measurements there are statistical specifications to be complied with.Furthermore there are concrete specifications on the calibration of the test systems and internal quality checks to be implemented. As far as external quality checks are concerned, each laboratory has to participate in four interlaboratory tests each year. These are organized by the Centre Suisse de Contrôle de Qualité (CSCQ) on behalf of the Swiss Federal Roads Authority. The laboratories which perform alcohol testing of blood samples from road traffic participants have to be accredited by the Swiss Federal Roads Authority. At present there are ten accredited laboratories in Switzerland.