Differentiation of Xylene Isomers by Chemical Ionization Mass Fragmentography

Abstract

Three kind of isomers of xylene and ethylbenzene were analyzed using a gas chromatogrph-chemical ionization mass spectrometer with mass fragmentograhy technique to find any difference between these isomers in the various conditions, such as different reagent gases(CH4, i-C4H10 and NH3)and ion source temperature(200°C∼280°C). With iso-buthane as a reagent gas, the peak intensity of m/e 107(QM+)and the peak intensity ratio of m/e 106 to m/e 107 show remarkable differences between m-xylene and the other isomers at 200°C of the ion source temperature, and the differences decrease with increasing temperature. With ammonia as a reagent gas, the peak intensity of m/e 106 and the peak intensity ratio of m/e 108 to m/e 106 show much differences between p-xylene and the other isomers, and the differences are unchanged by the ion source temperature 200°∼280°C. Peak intensity ratio of m/e 105 to m/e 107 of ethylbenzene is much higher than the one of xylene isomers with iso-buthane as a reagent gas at 200°C of ion source temperature, and the differences decrease with increasing temperature.