The effect of trialkylamines on the repsonse of the electron-capture detector to acridine

Abstract

The normal electron-capture detector response to acridine is shown to be complicated by a positive ion-molecule reaction sequence. Because of its very high proton affinity, acridine is readily protonated inthe electron-capture detector when clean carrier gas is used. This positive ion-molecule sequence has an effect on electron density which is dominant over the electron capture reaction with small concentrations of acridine so that an inverted response is then observed. At higher concentrations of acridine, complex peak shapes are observed which reflect the competition between the electron capture reaction and the positive ion sequence. The positive ion sequence is partially stabilized and the electron-capture detector reesponse to acridine is simplified by the addition of trimethylamine to the carrier gas. The positive ion sequence is completely stabilized by triethylamine. The positive ions formed by the presence of the alkylamines are not simply the (M + 1) + ions as were expected. Rather, for trimethylamine the (M − 1) + ion and for triethylamine the (M − 15) + ion are dominat. It is shown that these ions are produced in abundance only in a relatively pure nitrogen medium. These ions are shwn to be more stable than the corresponding (M + 1) + ions which are also observed in lower abundance.