Hydrodynamic volume average molecular weight

By appropriate calibration, the chromatogram is converted to a tme (fingerprint) molecular weight distribution curve, from which all pertinent averages are easily calculated. The most reliable calibration is based on the relationship between the product [ft]M (intrinsic viscosity multiplied by molecular weight) and elution volume (or time), following Flor/s equation (3-7) which relates intrinsic viscosity to hydrodynamic volume and molecular weight. 

Benoit and co-workers [18] proposed that the hydrodynamic volume, Vr which is proportional to the product of [17] and M, where [17] is the intrinsic viscosity of the polymer in the SEC eluent, may be used as the universal calibration parameter (Fig. 18.3). For linear polymers, interpretation in terms of molecular weight is straightforward. If the Mark-Houwink-Sakurada constants K and a are known, log [t7]M can be written log M1+ + log K, and VT can be directly related to M. The size-average molecular weight, Mz, is defined by this process ... 

A summary of the results obtained from GPC/DV on the first day and the third day after solution preparation is shown in Table II. For Red Oak and RO PO, the number average molecular weight decreased by approximately 6% from the first day to the third day. However, the intrinsic viscosities increased. According to traditional polymer solution theory (42), the product of intrinsic viscosity and molecular weight yields the hydrodynamic volume specifically, it has been shown that the molecular weight that... 

Table II. Viscometric and GPC Weight Average Molecular Weight Data Using the Hydrodynamic Volume (Universal Calibration Model)...

The response (a decrease of viscosity) is a direct consequence of the action of the enzyme on its substrate, since the splitting of the glycosidic bonds gives a decrease in the viscosimetric average molecular weight and hydrodynamic volume of the hyaluronan chains and hence a decrease in the intrinsic and relative viscosities. With this method the rate at different concentrations cannot be compared because the initial viscosities are different and rheological measurements do not coincide. To eliminate these problems, a kinetic dilution methodology for the viscosimetric study of the substrate concentration dependence of the action of hyaluronidase was proposed [135,136]. We were able to determine the rate of reaction, expressed as the number of moles of bonds broken per unit of time, from viscosimetric data [136]. 

SEC/LALLS. The weight-average molecular weights determined by SEC/LALLS are the same as those determined by SEC with universal calibration, indicating the cationic PVP/DMAEMA copolymers are separated by hydrodynamic volumes in SEC. The overlays of molecular weight distributions of the cationic PVP/DMAEMA copolymers are shown in Figure 11. 

---