We have blogged in the past on different types of phase bleed & how much background CO2 is acceptable in an MS system. This example is cause for troubleshooting a variety of things such as; a leak in the system, proper operating temperatures, sample matrix, etc. The approach assumes this is column bleed. Without the luxury of MS there is no easy way of knowing and most of us are left assuming that it must be column bleed. A closer examination of the baseline indicates the presence of hydrocarbons. Alkanes have a characteristic pattern with ion spacing of m/z 14 (loss of CH2) versus column bleed (m/z 207). In this case the m/z 207 is 20X less than the base peak for the alkane (m/z 57). Proper gas management (hydrocarbon traps) & conditioning any newly installed metal parts will minimize hydrocarbon background. The hydrocarbons in this chromatogram (cutting oils) can be traced back to an experimental injection port that was not cleaned & conditioned prior to analysis.
