Assigned formula of complex mixture FT-ICR MS datasets

The dataset included is of formula assigned from FT-ICR MS data for samples of Suwannee River fulvic acid (SRFA) and Suwannee River natural organic matter (SRNOM) (both are standards from the International Humic Substances Society) using a variety of ionisation sources. This includes electrospray ionisation (ESI), matrix assisted laser desorption/ionisation (MALDI) and matrix free laser desorption/ionisation (LDI).