Abstract Major and trace elements in four standard and reference samples of aquatic humic substances — Suwannee River Fulvic Acid, Suwannee River Humic Acid, Nordic Reference Fulvic Acid and the NIVA-Concentrate, have been determined using instrumental neutron activation analysis (INAA). The NIVA-Concentrate is isolated by low pressure and low temperature evaporation and includes all dissolved non-volatile carbon present in the water. The other three humic samples are isolated according to the IHSS standard methods and includes app. 50 % of the dissolved organic carbon present in the water. Due to the isolation method the NIVA-Concentrate contains both the highest concentrations and the highest number of elements. Except for high levels of Ag and Hg in Suwannee River Humic Acid, there seems to be only minor differences between the different samples of aquatic humic substances isolated according to the IHSS standard method.