ガスクロマトグラフィー
Alcohol levels within the body are usually detected through blood or breath. The best way to identify endogenous ethanol in the bloodstream is through gas chromatography. Gas chromatography is where the breath or blood is heated so that the different components of the vapor or blood separate.  The volatiles then pass through a chromatograph that isolates ethanol from the smaller volatiles so that it can be quantified.