What is Mass Discrimination?
Mass discrimination is defined as an unrepresentative sampling from the injector to the column of low and high molecular weight components.
Discrimination - Splitless Time
The top chromatogram is an example of what happens when the purge time is too short. As can be seen, C22 has not had enough time to vaporize completely. The sample has spent a little over 10sec in the injection port and has not gained enough energy from the liner to completely vaporize the hydrocarbons. There is much high boiling point discrimination.
The bottom chromatogram shows the same sample under the same conditions except the purge flow turns on one minute after the start of the run. The first thing you will notice between the two chromatograms is the difference in response of the heavier compounds. The high boilers have now been able to absorb enough energy from the liner to vaporize completely. Another major difference is the increase in height and area of all the compounds in the chromatogram. The peaks second chromatogram are almost twice the height than the peaks in the first chromatogram.
|<< Splitless Injection|