Question

Imagine that the injector temperature on a GC was set too low so that the sample vaporized rather slowly. The mobile phase flow is precisely controlled. INCLUDE EXPLANATIONS with your answers to each of the following questions. a) Will the retention factor, k’, increase, decrease, or remain the same? b) Will the column efficiency, H, increase, decrease, or remain the same? c) Will the peak height appear to increase, decrease, or remain the same? d) Will the peak area appear to increase, decrease, or remain the same? e) Would peak heights or peak areas be preferred for quantitative measurements?

Answer 1

In the GC all the sample must be avaporated prior to it passing through the column.

If however, the injector temperature was set low so that the sample vaporization was rather slow,

a) The retention factor k' which is where the component comes out would reamin the same as the component would come out at the same time.

b) Column effeciency would decreases as the sample would not be able to get separated in this condition. Peaks wuld be broad due to slow vaporization.

c) Peak height would be lower (decrease) as not all of the sample is evaorated at the injector which would give lower concentration.

d) Peak area would again decrease due to lower concentration of component.

e) Peak areas and peak height would not be choosen for the quantitative measurements. Incorrect results would be obtained with lower precision and accuracy.