Commercial chitosan typically has a maximum molecular weight in the range of 100 to 800 kDa. Molecular weight directly impacts the functionality of chitosan in all applications. Several methods have been employed to determine the molecular weight of chitosan. One of the most common methods in determining molecular weight is size exclusion chromatography. You can also follow the attached link.

Hi,

Determination of Viscosity Average Molecular Weight of Polymer is very best for molecular weight of chitosan

Objectives:

Theory:

Viscosity is an internal property of a fluid that offers resistance to flow. It is due to the internal friction of molecules and  mainly depends on the nature & temperature of the liquid.

Many methods are available for measuring viscosity of polymer solution. The Ostwald method is a simple method for the measurement of viscosity, in which viscosity of liquid is measured by comparing the viscosity of an unknown liquid with that of liquid whose viscosity is known. In this method viscosity of liquid is measured by comparing the flow times of two liquids of equal volumes using same viscometer.

Consider two liquids are passing through a capillary of same viscometer. Then the coefficient of viscosity of liquid (η2) is given by equation

📷

Here t1 and t2 are the time of flow of the liquids and ρ1 and ρ2 are the respective densities. And η1 is the coefficient of viscosity of water.

For a given liquid η has a specific value at the same temperature.

Various mixtures of two non-interacting liquids viscosities will lie among the viscosities of those pure components.

The time of flow of liquid depends on the viscosity and composition. In this method the flow times are measured for different known compositions and a graph is plot for time of flow and compositions. The unknown composition can be determined by plotting a graph for the time of flow and compositions.

The molecular weight of the polymer is measured by using viscometer and the molecular weight obtained by this technique is called viscosity average molecular weight. The molecular weight of the polymer solution is very high so the viscosity of polymer solution is very high compared to that of pure solvent. 

From the Mark-Houwink equation the relationship among the molecular weight and viscosity are given below

📷

Where 📷 is the intrinsic viscosity , 📷 is Molecular weight, 📷 and 📷 are constants for a particular polymer solvent  system.

If we know the 📷 and 📷 values for a given polymer solution the intrinsic viscosity and molecular weight can be calculate using the above equation.

MALDI-TOF-MS.

Dr Priyanka ... Hi

by Determination of Viscosity or Gel filtration .

regard

Mass spectroscopy or gc chromatography you can try

Using viscosity average molecular weight is an appropriate method.