SELECTION AND USE OF MASS REFERENCE-STANDARDS

This chapter discusses selection and use of mass reference standards. Reference compounds are required for data system and instrument calibration, high-resolution mass measurements, instrument tuning, and sensitivity/resolution performance checks. A reference compound should be readily available, should provide a series of regularly spaced peaks of good intensity over the desired mass range in the selected ionization mode, and should be volatile enough to be pumped away or otherwise easily removed from the ion source. Perfluorokerosene (PFK) is a mixture of perfluoronated alkanes that is widely employed in electron ionization (EI) mass spectrometry and is available in low (PFK-L) and high (PFK-H) boiling mixtures. PFK-L has ions useful to about 600 mass units and PFK-H is useful to about 900 mass units. PFK can be introduced through a heated inlet system or from a direct insertion probe. Absorbing the PFK on a small amount of charcoal in the direct-probe crucible gives better control over the rate of volatilization. © 1990, Elsevier Inc. All rights reserved.