A major problem in the analysis of nitroglycerin (propanetriol trinitrate, GTN) and its metabolites [propanetriol 1,2-dinitrate (1,2-GDN) and propanetriol 1,3-dinitrate (1,3-GDN)] has been the adsorption of the nitro compounds to glass apparatus during sample preparation or injection. In this paper we present a method determining GTN, 1,2-GDN and 1,3-GDN in plasma at low nanomolar level using capillary gas chromatography with electron-capture detection. The detection limits are about 0.2 nM in plasma. Adsorption of the nitro compounds to glassware is prevented by using triethylamine, giving a simple sample preparation and accurate results. Thus, the laborious and time-consuming silanization of the glassware is avoided.