Using solution equilibria to determine average molecular weight of the Suwannee River fulvic acids Original Research Article

A systematic treatment of chemical equilibria is used to determine the average molecular weight (AMW) of the Suwannee River fulvic acids directly from aqueous solutions. In addition to molecular weight determination, parameters such as equilibrium constant and reaction stoichiometry can be calculated; in this approach, it is not necessary to measure the initial mass of unknown analytes. The key experimental and theoretical considerations for systematic treatment of equilibrium and determination of unknown parameters are addressed. Results from the equilibrium considerations yield an AMW of 551±10 Da for the Suwannee River fulvic acid sample analyzed in this study. In addition to the Suwannee River fulvic acid sample, experimental data for selected monoprotic and polyprotic acids are presented and discussed.