When a driver is arrested for suspicion of driving under the influence of alcohol, the blood alcohol content is determined to see if it exceeds the legal limit. In cases where there is an accident, injury, or other serious consequence, the blood alcohol is usually determined directly, by analyzing a blood sample by gas chromatography.

A 5.0 mL blood sample from a suspect is spiked with 0.500 mL of aqueous 1% propanol internal standard. A 10 μL portion of the mixture is injected into the GC, and the peak areas are recorded. Standards are treated in the same way. The following results were obtained:

Please report the % EtOH (wt/vol) in the blood sample, use the relative uncertainty as estimated by the spreadsheet below to determine the absolute uncertainty of this measurement. Use the absolute uncertainty to determine the appropriate significant figures for you answer.

 

% ELOH (wt/vol) Peak Area EtOH Peak Area PrOH 0.020 114 457 0.050 278 449 0.100 561 471 0.150 845 453 0.200 1070 447 unknown 782 455