I want to measure the molecular weight distribution of a linear polyester (polylactide, poly(e-caprolactone) or a similar polymer) using GPC. As far as I know, it is usually done with a refractive index detecor.
Our device is equipped with a UV/Vis detector. Could I use it? The solutions usually appear transparent, but still...
UV/Vis or photo-diode array respond to sample concentration and light absorption. If you sample is transparent that means it is not absorbing any Vis light but there might be wavelengths of UV light being absorbed by your sample. UV/Vis detectors work according to beers law that is why they are responsive to sample concentration and can be used as a concentration detector or as the replacement of refractive index detector.
Also,
UV/Vis detector is used for the molecular weight distribution
But it can not be used in your case. The problem or the biggest limitation of UV/Vis detector is that the material being analyzed must have a chromophore in order to produce a signal.
Thank you!
"Is it possible to measure the molecular weight distribution of a polyester using a UV/Vis detector"?
No. A basic requirement of the analysis method is that it requires a suitable detector which can detect the sample. Polyesters do not have bond structures which absorb light at high enough levels to be seen by most UV detectors (especially when you consider that the mobile phase used for the analysis will absorb and obscure the light in the range that you would try to "see" the sample in).
The most commonly used detector for these samples using HPLC is the refrective index detector (RID) as you have noted. RID does not have the mobile phase limitations that UV/VIS does so will enable detection using solvents which fully dissolve the samples under test.
Hello, viscosity can give an approximative idea of molecular weight. You may find litterature of interest in macromolecule journal.
KR, Nabyl
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