General model for the separation of large molecules by gradient elution

Characterization of low-molar-mass polymers by gradient polymer elution chromatography I. Practical parameters and applications of the analysis of polyester resins under reversed phase conditions

“…For sample PE1 for instance, a value of 80% THF is found for the cloud point of a 40 mg/ml sample at 35°C, whereas ~p¢ is 81%. Obviously, a correspondence between cloud point and ~Pe does not necessarily mean a retention process that is governed by solubility effects, which is accordance with the findings of other workers [28]. It must be kept in mind, however, that for relatively low-molar-mass polymers, the cloud point is strongly dependent on the initial concentration.…”

“…A case where solubility and sorption both influence the separation has also been studied for polystyrene by other workers [28].…”

“…This observation further supports the idea that sorption effects are dominant in the chromatographic process. If the separation was mainly determined by solubility effects, a clear increase of retention with increasing sample load should have been observed [3,28]. The high loadability can be contributed to the relatively low-molar-mass of the investigated polymer.…”

Characterization of low-molar-mass polymers by gradient polymer elution chromatography II. Solubility effects in the analysis of polyester resins under reversed-phase conditions

“…This is further confirmed by the fact that retention time of the peak top increases when sample load is increased, which is illustrated in Table 4. When sorption effects would contribute to the separation, no dependency or decreasing retention times due to overloading should have been observed [16,29].…”

“…For polystyrenes under reversed-phase conditions, using a THF-water system values of a=0.22 and b =0.5 are reported [29,30].…”