DECREASE OF OXYGEN INTERFERENCE ON HUMIC ACID STRUCTURE ALTERATION DURING ISOLATION UDC 520.84:641

When dealing with a soil source, separation of humic and fulvic acids (HA and FA) from humin is usually obtained by alkaline extraction. Undesirable feature of this isolation method is that, under alkaline conditions, oxidation of HA occurs, in contact with air. This is, in part, overcome by isolation in N2 atmosphere (IHSS method). However, for isolation of even less altered material, the presence of O2 in the very alkaline extraction solution (AES) should not be neglected, although it usually is. In this paper we investigated the effect of MnSO4, on O2 level decrease in AES (modified IHSS method). HAs isolated by IHSS and modified IHSS methods were characterized by oxygen containing functional group determination, UV/VIS spectrophotometry and FT-IR spectrophotometry. Obtained data have shown that HA isolated by modified IHSS method, with deoxygenated AES, has less altered structure.