Protocol for the characterization of oceanic particles via flow cytometricsorting and direct temperature-resolved mass spectrometry

This paper presents a protocol for applying now cytometric (FC) sorting and direct temperature-resolved mass spectrometry (DT-MS) to oceanic particula te organic matter (POM) samples. Flow cytometric sorting allows the physica l separation of particle subclasses on the basis of morphological and chemi cal criteria including size, shape, and autofluorescence characteristics. D irect temperature-resolved mass spectrometry is a rapid (similar to 2-min) measurement that provides fingerprints of molecular-level characteristics a cross a wide range of compound classes, including both desorbable and pyrol yzable components. The resulting DT-MS data, therefore, can bridge the gap between information available from bulk measurements, such as elemental ana lysis, and information derived from detailed but laborious compound-class-s pecific analyses. In addition, the sensitivity of DT-MS (which requires onl y microgram quantities of sample) allows it to be used in conjunction with now cytometric sorting. In this study, the sample-handling procedures requi red by these techniques are described in detail and shown to yield useful, representative results.