An investigation of standard compounds for evaluating instrument performance in positive ion and negative ion chemical ionization mass spectrometry

Abstract

Decafluorotriphenylphosphine has been shown to be a useful compound for checking the overall performance of gas chromatography mass spectrometry systems in the electron impact (EI) mode of operation. This paper reports the results obtained on several compounds evaluated for their utility in checking mass spectrometric performance in the chemical ionization mode of operation. The ideal compound should be capable of being admitted to the ion source from both the solid probe inlet and the gas chromatographic inlet, should respond in both positive ion and negative ion modes, should have as high a molecular weight as possible (preferably > 400), should generate an abundant ion indicative of the molecular weight and several significant fragment ions covering a wide mass range in positive ion chemical ionization (CH4), and should generate less fragmentation in positive ion chemical ionization with less exothermic reagent gases. Following an evaluation which included such compounds as benzophenone, decafluorotriphenylphosphine, octacosane (n-C28H58), triacontane (n-C30H62), and methyl stearate, lauryl laurate (mol. wt = 368) was found to offer the best compromise in satisfying these criteria.