Resumen de Was the Driver Drunk? An Instrumental Methods Experiment for the Determination of Blood Alcohol Content
J. L. Zabzdyr, Sheri J. Lillard
Introducing forensic scenarios into the instrumental laboratory is a simple yet effective strategy to give students the opportunity to perform realistic experiments and to learn proper analytical techniques. In this laboratory experiment, which is designed for upper-division students in an instrumental methods course, unknown ethanol concentrations are quantitated in simulated serum samples using headspace gas chromatography (GC) with flame ionization detection. For the quantitative determination of blood alcohol content (BAC) in cases where drunk driving is suspected, GC is considered the most reliable method. Furthermore, headspace sampling helps to eliminate interferences from biological matrices such as blood or serum. An unknown sample of ethanol in serum, which brackets the 0.080 g/mL legal limit (e.g., BAC 0.075-0.087 g/mL), is given to the student for measurement. Both external and internal standardization methods are used for calibration. The students calculate serum alcohol concentration based on the measurement of their unknown sample using each calibration curve, and the results from each calibration method are compared and discussed in terms of accuracy. They then use a conversion factor to calculate BAC from serum alcohol concentration and use their results to determine if the "suspected driver" was driving under the influence.
