[ina]

could you have predicted the exit order of the components without determining their retention times? what factors determine this?

[JGK]

What compounds are you talking about?

and

more important, what are the chromatography conditions?


The elution order  may depend on the selectivity of the column or may be related to boiling point without any information how can we help you.

[marutikmv]

could you have predicted the exit order of the components without determining their retention times? what factors determine this?

If your question pertaining to GC analysis, the elution order is based on the boiling point of that particular analyte in that solvent.

[DrCMS]

could you have predicted the exit order of the components without determining their retention times? what factors determine this?

If your question pertaining to GC analysis, the elution order is based on the boiling point of that particular analyte in that solvent.

NO NO NO IT DOES NOT. 
Only under certain conditions is the seperation related to boiling points, and not in solvent.

[realmjumper99]

it has to do with interactions between your analyte and what the coating in the GC is. For instance, if your GC is reverse phase (meaning it is coated with a non-polar substance), it will be more likely that nonpolar groups will stay in the GC longer than polar groups because of the whole "like dissolves like" type of interactions. Size is also a factor. Larger molecules are more hindered as they pass through the coating of the GC so they are also going to elute later than smaller molecules of the same polarity.

[JGK]

The term "Reverse Phase" does not exist in GC

In LC "Normal Phase" is organic (relatively non-polar) mobile phase and polar stationary phase. "Reverse Phase" is aqueous (relatively polar) mobile phase and non-polar stationary phase.

In GC the mobile phase (carrier gas) does not change so the only differentiation is between the stationary phases.

Non-polar materials will be reatained by nonpolar coatings with RT dependent on temperature,  column length and film thickness. However, compounds of the same class will alwasys elute from theses columns in order of their boiling points.

Alternative phase coatings or column types mat proveide alternate selectivities

[wipeout]

You can use Quantitative Relationships Structure Retention Models. You need carry out some experiments with similar compounds and fit some model (linear, PLS, PCR, etc) where your independent variables are i.e: boiling point, topological index, number of atoms, number of unsaturated bonds, etc. In that way you can "predict" retention time of similar compounds.