Effect of additives in a carrier gas on the behavior of ions in an ion-mobility increment spectrometer

The effect of additives (ethanol, acetic acid, water, chloroform, and acetone) in air used as the carrier gas on the changes in the spectra of the H+(C(6)H(5)NH(2)) ion was studied for an ion-mobility increment spectrometer (IMIS) operating in tandem with a mass spectrometer (MS). It was shown that the presence of additives could improve both the resolution of the instrument and the sensitivity of the method. The resolving power was increased fourfold using air saturated with an ethanol vapor, while the sensitivity was increased 11-fold upon adding a mixture of ethanol and acetic acid to the carrier gas. The dependences on the concentration of the additives indicate that the formation of the clusters is the reason for these effects. The presence of an ethanol vapor in the carrier gas almost completely eliminates the effect of the present water vapor; therefore, air saturated with ethanol vapors can be used in the IMIS-MS instruments without drying.