Humic acid quality: Using oxalic acid as precipitating agent

Abstract

Two modifications of the standard procedure for the isolation of humic acids (HA) from peat samples have been explored. The modifications comprise a Soxhlet extraction of the freeze-dried peat sample with an organic solvent and the use of organic acids for the precipitation of the HA fraction. The organic extraction effectively removes organo-soluble impurities (up to 12%) without obvious signs of alteration or loss of humic material (Meyer G, Klöcking R, Optimising the protocol for the isolation of humic substances with regards to their use in biological systems. Proceedings of the Arbeitstagung Torf und Huminstoffe, Zittau, Germany 28-30/09/11, 2011). The use of organic acids as precipitant aims at the halogen- and mineral acid-free preparation of HA. Here, the quality of HA obtained using the modified procedure is compared to those obtained by traditional HCl precipitation.