By the new Liquid Chromatography Distillation (LCD) method, these Chinese researchers found similar trends, to those you gave in the last 2 lines of your question, upon their study on heavy oil. You will see in Table 2 that , in general, when retention time decreases, the boiling point increases for related compounds:

https://www.hilarispublisher.com/open-access/study-on-the-determination-of-boiling-point-distribution-of-heavy-oil-by-the-new-method-2161-0525.1000224.pdf

This is a new interesting information for me so I thank you for your question.

Dear Alexander Sinko,

from my experience I can say that in gas chromatography a separation is not performed by boiling points but by polarity.

The boiling point certainly follows the polarity of a substance , but the polarity is also structure-dependent. Therefore, branching of the C-sting or changing the position of the functional group can influence the separation in such a way that it no longer corresponds to the boiling points.

According to my observations, the correspondence between retention time and boiling point is greatest for very apolar separation phases. If the phase polarity becomes higher, this agreement increasingly fades.

Since you are probably running GC-MS with a universal moderately polar column, typical would be an HP5-MS, Factor Four 5 MS, RTX5-MS or comparable, this column polarity will limit the separation by boiling point.

With much more polar separation columns like DB1701, FFAP, Carbowax, this effect will be intensified.

I hope to have helped with this explanation.

Many greetings and stay healthy

Joachim Horst

Dear Mr. Joachim Horst

I appreciate very well your explanation.

It helps me so much to understand the correlation between boiling point and retention time.

Many thanks to you,