Abstract:
We propose and demonstrate an approach involving use of C18 solid phase disk extraction coupled with high resolution mass spectrometry for obtaining non-invasive molecular level information on dissolved organic matter (DOM) from river water. With this approach, DOM extraction from acidified natural water can be achieved rapidly with a simple filtration setup at a remote field site. From total organic carbon and UV-Vis absorbance measurements, we show that a large portion (over 60%) of the original DOM in water is recovered without the interference of salts. NMR analysis indicates that the C18-isolated material has a similar distribution of functional groups as the original DOM but 2-D NMR details are greatly enhanced. Electrospray ionization mass spectrometry and high resolution mass spectrometry were employed to study DOM at molecular level. Highly resolved mass spectra of DOM (resolving power > 80,000 at m/z <600) reveal that there are many pairs of peaks that differ by the exact masses of –H2, –O, or –CH2 indicative of possible homologous series of structures.
