Question

1 a) Explain why the accuracy of the internal standard method does not depend on the accuracy of the volume of sample injected into the GC?

b) What result would increasing the length of the column have on the observed chromatogram?

Answer 1

The internal standard for a chromatography is a species that you use as a reference, given that it has a very similar behavior to the one of your analyte, which is the reason for the chromatographic analysis. Regardless of the volume you inject into the gas chromatography, the analyte and the internal standard you chose will behave similarly and hence render a reliable reference of what the analyte's concentration is throughout the process.

If you increase the length of the column, the flow rate is expected to remain equal, given that your diameter did not change. More time in the column with the same flow rate would most likely render better resolution in the peaks the chromatogram shows. (This answer depends on whether or not you have a reference chromatogram) It's very likely that the peaks are more defined and have better resolution, given that the species spent more time in the column, given a greater length.