A series of alkyl chloroformates has been investigated for its ability to form carbamates with some tertiary amines. The reaction is promoted by a base catalyst and performed for 30 minutes on a boiling water bath. Chloroformates of the benzyl type permitted the introduction of electrophore groups, thereby making possible the direct determination of tertiary amines as carbamates in the electron capture detector. Pentafluorobenzyl chloroformate was found to be the best reagent due to high sensitivity, excellent gas chromatographic properties and good stability. The minimum detectable quantity is on the order of 1 × 10−16 moles/sec, or corresponding to about 3 pg in an injected sample. The reagent has been tested for quantitative determinations in the range 50–800 µg with recoveries of 100 ± 2.7% at the 200 µg level. The reagent has been used in studies of many tertiary amines today used as drugs, e.g. imipramine and its analogues, amitriptyline and diphenhydramine.