Perhaps the most difficult step in any GC-MS analysis is the sample introduction. Solid or liquid samples need to be converted to the gas phase and then efficiently transported onto the GC column. The primary aim with all sampling techniques is to ensure a representative and homogeneous gaseous aliquot of the sample under investigation is delivered to the GC column. This module will explore the main GC considerations when using MS detectors.

At the end of this unit you should be able to highlight the GC parameters which are of particular importance when using MS detection; describe the main sample inlet types used for GC-MS and the relative merits of each type; make a suitable choice of capillary column bonded phase and column dimension for a particular separation type in GC-MS; demonstrate awareness of the impact of column bleed on MS hardware; choose appropriate GC carrier gas flow rates for the GC-MS experiment and be aware of the potential impact of high carrier flow on the GC-MS vacuum.

Topics include: 

• Sample introduction
• Split injection - overview
• Split injection - setting split ratio
• Split injection - sample discrimination
• Split injection - injection volume
• Splitless injection - overview
• Splitless injection - purging the inlet
• Splitless injection - analyte focusing
• Splitless injection - solvent choice
• PVT inlets
• Headspace sampling
• Headspace autosamplers
• Headspace analysis important parameters