Molecular structure of fulvic acids by electrospray with quadrupole time-of-flight mass spectrometry

Characterisation of the molecular structure of aquatic fulvic acids (FA) ha s been performed using a quadrupole time-of-flight (Q-TOF) mass spectromete r equipped with an electrospray ionisation interface. Molecular masses cent red around 450 Da and sinusoidal spectral distributions have been obtained for all fulvic acids. Tandem mass spectrometry (MS/MS) experiments showed l osses of 18 Da (H2O) and 44 Da (CO2), and possible molecular structures wer e determined for the first time to our knowledge. A methodology is reported for evaluating the average elemental composition of]FA from high-resolutio n mass spectra by processing post-acquisition data calculations using molec ular size distributions and atomic compositions of ions. The results are fo und to be consistent with elemental analysis data. Copyright (C) 2001 John Wiley & Sons, Ltd.