FORENSIC CHEMISTRY LABORATORY MANUAL

by R.Q. Thompson; Oberlin College

ANALYSIS OF A SIMULATED BLOOD SAMPLE FOR ETHANOL

Objective

To determine the concentration of ethanol in a blood sample; to see if the person being tested was legally drunk.

 

Sample

A simulated blood plasma with added ethanol. Store the aqueous solution in a tightly closed vial in the refrigerator; the solution is stable for at least one month.

 

Reagents

 

Ethanol (analyte), n-propanol (internal standard)

Standard Reference Material

The standard reference material is simulated blood plasma with a concentration of 0.10% (w/v) ethanol. Store the aqueous solution in a tightly closed vial in the refrigerator; the solution is stable for at least one month.

 

Method

 

Gas chromatography; direct aqueous injection
Special equipment

Capillary gas chromatograph with thick-film Carbowax column (e.g. 30 m x 0.25 mm x 0.5 µm) and flame ionization detector

 

Procedure

 

For instructor (detailed) ; For student (brief)

Typical results

Chromatogram: 1 µL injection of liquid sample at 1:40 split; isothermal separation at 70 degrees C; 1 mL/min helium flow; elution order is (1) ethanol (2) propanol

Calibration curve: (peak area ethanol / peak area propanol) vs. concentration of ethanol