Abstract
BACKGROUND: Numerous products manufactured from non-humic sources have flooded the market claiming to be fulvic acids. The challenge is finding an easy method to distinguish between products containing genuine fulvic fractions and those containing adulterants. UV spectrophotometry has been widely used to study the fulvic fraction extracted from humic substances, with multiple metrics derived from UV absorption spectra developed and implemented by researchers. OBJECTIVE: Leverage ten indices that are characteristic features of the UV spectra of hydrophobic fulvic acids to differentiate products containing authentic fulvic fractions from those containing adulterants. METHODS: Fulvic fractions were diluted to 5 ppm carbon and UV spectra were obtained. Spectra were normalized and analyzed to calculate 10 different indices. The percent difference between the index values of the product and the corresponding index values for the Suwannee River fulvic acid (SRFA) and Pahokee peat fulvic acid (PPFA) standards were calculated. An equally weighted average for all 10 indices was calculated and a 70% cutoff value was used for the average percent error as a screening tool to distinguish products containing fulvic fractions from adulterants. RESULTS: Fifty-four test samples were analyzed, with nine samples being analyzed by two different laboratories using the established method. Fourteen of the 25 commercial products studied were found to contain fulvic fractions. Increased metal ion concentration within the investigated range did not impact the average percent error calculated, nor did varying the total organic carbon concentrations of the test portions within the range of 1-10 ppm. CONCLUSION: The method investigated could be a suitable screening tool for most commercial products and is capable of accurately distinguishing products that contain fulvic fractions. HIGHLIGHTS: The method accurately found all 11 fulvic fractions isolated from known humic substances as fulvic, and all 11 test samples prepared from non-humified materials as non-fulvic.