The polydispersity index (Mw/MN) of the polymers ranged from 2.492 for pectin extracted with acetic acid to 1.250 for pectin extracted with nitric acid. The highest Mw/MN for pectin extracted with acetic acid indicating a broader range of polymer size distribution in this sample.
The differential molar mass distribution for pectins obtained with different acids under microwave heating is shown in Fig. 6. It is possible to observe that the samples shown a uniform distribution of sizes. The curves show how much material (differential weight fraction) is contained in any molar mass interval. It is possible to observe that the pectins obtained by extracting with nitric acid present a sharp peak, with the narrowest distribution, in accordance with its lower Mw/MN. By the other side, pectin extracted with acetic acid showed the wider distribution of molecules, between 2 × 104 g/mol and 2 × 106 g/mol.