To date, direct temperature-resolved mass spectrometry (DT-MS, a form of temperature-resolved, in-source pyrolysis mass spectrometry) has generally been used to provide qualitative views of the broad-band molecular-level characteristics of complex organic samples. In this paper low voltage electron impact (EI+) DT-MS is used to provide semi-quantitative information on molecular-level characteristics of marine particulate organic matter (POM) samples. This class of samples is analytically challenging for two main reasons. Firstly, it is difficult to obtain representative data sets in which sample sizes are sufficient for characterization. Secondly, marine organic matter samples contain many identifiable compound classes in conjunction with a substantial percentage of as-of-yet uncharacterizable material. As a first step toward quantitation, DT-MS analysis of selected standards was used to determine relative response factors of common compound classes identified in marine organic matter. These response factors were then used to quantify the relative contribution of the compound classes in two natural POM samples. The potential of DT-MS as a quantitative technique was then further explored by comparing DT-MS determinations of particulate organic carbon to chlorophyll ratios (POC/chl) in natural POM samples with the same ratios determined by elemental analysis and liquid chromatography (HPLC), a technique currently employed by marine chemists.
Bibliographical noteFunding Information:
This work was funded by the U.S. National Science Foundation (OCE-9503455), the U.S. Department of Energy—Ocean Margins Project (DE-FG02-92ER61428) and the Foundation of Fundamental Research on Matter (FOM research program no. 28, ‘Mass Spectrometry of Macromolecular Systems’) which is financially supported by the Dutch Organization of Scientific Research (NWO). It is Woods Hole Oceanographic Institution contribution #9845. Thanks to Carl Johnson (WHOI) and Jos Pureveen (FOM) for their help with mass spectrometry, Gert Eijkel (FOM) and William Little (WHOI) for guidance through the multivariate analysis programs, Robert Nelson and Liz Kujawinski for their help with the CHN analyses, Daniel Repeta for HPLC instruction, and the captain and crew of the R/V Endeavor for assistance with sampling.