Gas Chromatography Questions and Answers

Answer: A

The modulation period sets a hard deadline: whatever the second column has not eluted when the next slice arrives is lost or overlapped. Detector speed is a real requirement that follows from this rather than causing it, and neither overheating nor gas consumption is limiting. A constraint imposed by one part of a system on another, rather than by any component's own capability, is what makes such designs so tightly coupled.

Answer: B

Petroleum, essential oils and environmental extracts contain far more components than any single column's peak capacity can resolve, and only a second independent dimension helps. A pure compound, a single analyte and a lone impurity are all comfortably handled by one column. Reserving a complex technique for the problem that genuinely requires it is what keeps a laboratory productive, since the data handling alone is considerable.

Answer: C

Peak capacity counts how many peaks could be fitted side by side across the whole chromatogram at the resolution achieved, and it is the figure a second dimension multiplies. Sample capacity, plate number and detector range are distinct quantities. That two dimensions multiply rather than add their capacities is why the technique gains so much, and why the second column need not be as good as the first.