Evaluation of a Spectrophotometric Method for Practical and Cost Effective Quantification of Fulvic Acid

Abstract

A large number of organic humic products are increasingly being applied worldwide especially in agricultural applications. Humic substances can be fractionated into three components: humic acid, fulvic acid and insoluble humin. A standard method based on acid precipitation is gaining acceptance for quantification of humic acid as the humic acid precipitates at pH < 2 and thus can be quantified by gravimetric measurements. However, the fulvic acid component remains in solution at all pH conditions and there is no practical and cost effective method available for measuring fulvic acid. This paper presents the results of our evaluation of spectrophotometric analysis of the fulvic acid content of commercial humic products. Based on the assumption that the optical properties of fulvic acids are independent of their sources, a calibration curve showing a linear relationship between varying concentrations of an IHSS standard fulvic acid and their UV/vis absorption at multiple wavelengths was established. The concentrations of fulvic acid in a variety of commercial products were then obtained by measuring the samples UV/vis absorption and applying the established calibration curve. The calculated fulvic acid concentrations were in reasonable agreement with the values obtained from carbon analysis of the test samples after corrections.

Permanent URL: http://hdl.handle.net/2047/d10006060