Liquid chromatography of synthetic polymers under critical conditions of enthalpic interactions 4: Sample recovery

Abstract

Reduced sample recovery is a frequent feature of LC of macromolecules under critical conditions of enthalpic interactions (LC CC). Several methods of assessment of LC CC sample recovery are compared. A novel approach is based on an online combination of the. The LC CC column with a noninteractive SEC column. It provides not only the amount but also the molar mass of the eluted/withheld polymer. The procedure was tested with poly(methyl methacrylate), bare silica gel column packings, and "critical eluent" tetrahydrofuran/toluene. It was shown that macromolecules with higher molar masses were preferentially trapped within the LC CC column packing so that the eluted part of the sample was no longer representative. The incomplete polymer elution can make the LC CC polymer analyses susceptible to significant experimental errors.

Critical assessment of “critical” liquid chromatography of block copolymers

“…Substantial fraction of sample may stay retained in the LC CC column . Detailed studies of this occurrence revealed the fast decrease of sample recovery with the increasing polymer molar mass.…”

“…Detailed studies of this occurrence revealed the fast decrease of sample recovery with the increasing polymer molar mass. Larger macromolecules were preferably retained within the LC CC column from the broad molar mass distributed samples so that the results of their characterization were biased. Pore‐excluded macromolecules were often entirely held back in the column.…”

Purity of double hydrophilic block copolymers revealed by capillary electrophoresis in the critical conditions

“…Although the linearity of the UV detector response for the PAA homopolymers is not as high as wanted, establishing linearity with an ELSD detector can be equally as difficult and in some cases there is no linear response between the detector signal and concentration of the polymer [71,72], as the molar mass of the polymer also influences the ELSD response. The imperfect linearity of the detector response for the PAA homopolymers is likely due to variations in injection volumes between injections since the samples were injected hydrodynamically and the pressure may vary from injection to injection.…”

Structural characterization of telechelic polyisobutylene diol

“…[19] Matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS) provides valuable information on the polymer end group structure.…”