MICROSCALE CHARACTERIZATION OF ALGAL AND RELATED PARTICULATE ORGANIC-MATTER BY DIRECT TEMPERATURE-RESOLVED MASS-SPECTROMETRY

In this paper we report a preliminary investigation of laboratory alga l cultures and natural populations of marine particles utilizing Direc t (i.e. ''in-source'') Temperature-resolved Mass spectrometry (DT-MS). With this technique the potential exists to characterize microgram qu antities of particulate organic matter (POM) at the molecular level. T wo particular aspects of the approach set DT-MS apart from previous py rolysis (Py)-MS investigations. First, temperature resolution allows c haracterization of both desorption (biolipid) and pyrolysis (biopolyme ric) products in a single measurement. Second, an improved sample inle t configuration enables compounds exhibiting a broad range of polariti es and molecular weights to be transmitted to the analyzer. The above features, coupled with the rapid analysis time (typically 5 min/sample ) and amenability to statistical data reduction procedures, renders DT -MS well suited for profiling or mapping molecular-level variations in POM composition at a spatial and temporal resolution hitherto impract ical using conventional biochemical assays. To illustrate the versatil ity of the approach and extent of (bio)chemical information available from DT-MS, we have analyzed a series of algal cultures together with selected POM samples collected in sediment traps and filtered from hyd rocasts. We have also exploited the inherent sensitivity of DT-MS, to obtain information on compositional variability between and, more sign ificantly, within particle size classes. Results of the latter, which was attained by conducting DT-MS measurements on particles sorted by f low cytometry, reveal substantial internal variations in chemical comp osition.