Fractionation by molecular weight

Note Pure analytes often show a comparatively sharp onset of desorption. Desorption then lasts for several scans until the sample is consumed. Finally, the intensity of the signals rapidly drops to zero again. In case of mixtures, some fractionation by molecular weight of the components is observed (Fig. 8.20). 

The experimental data on fractionation by molecular weight are given in 52,53). Fig. 2 b shows changes in the MWD of PVPD (oligomer) after binding part of it in a polycomplex with PAA (polymer)S2) it is clear that the experimental pattern (Fig. 2b) corresponds to the theoretical one (Fig. 2a), i.e., the high-molecular fraction binds in a polycomplex while the low molecular one remains in the solution. 

Wheeler, J.R., 1976. Fractionation by molecular weight of organic substances in Georgia coastal waters. Limnol. Oceanogr., 21 846—852. 

Eor m randomly distributed branch points in each molecule of a sample that has been fractionated by molecular weight, i.e., that is monodisperse, Zimm and Stockmayer [8] showed that for larger values of m, average values of g can be approximated by Eq. 2.25 for a functionality of 3 and by Eq. 2.26 for a functionality of 4. 

---