In gas chromatography, what primarily determines the elution order of volatile compounds?

In gas chromatography, the elution order of volatile compounds is primarily determined by their boiling points. Compounds with lower boiling points tend to vaporize more readily and move through the column faster than those with higher boiling points. As a result, in a gas chromatographic separation, the volatile substances that have the lowest boiling points will elute first, followed by those with progressively higher boiling points.

While molecular size, carbon content, and polarity can influence the behavior of compounds during separation, they do not primarily dictate the elution order in the context of gas chromatography. For instance, larger molecules may have higher boiling points due to greater intermolecular forces, and while polarity plays a role in interactions with the stationary phase, it is the volatility—as indicated by boiling point—that significantly impacts how quickly a compound moves through the system. This relationship is fundamental in predicting and controlling the elution sequence in gas chromatography.