Instrument: Isotope-ratio Mass Spectrometer
The Isotope-ratio Mass Spectrometer is a particular type of mass spectrometer used to measure the relative abundance of isotopes in a given sample (e.g. VG Prism II Isotope Ratio Mass-Spectrometer).
Costech ECS 4010 elemental analyzer (EA)
Finnigan Delta Plus XP isotope ratio mass spectrometer (IRMS)
Particulate organic samples (on GF/F filters) were fumigated with HCl, dried, then loaded into tin capsules and analyzed for particulate organic carbon (POC) and particulate organic nitrogen (PON) concentrations using a Costech ECS 4010 elemental analyzer (EA) coupled to Finnigan Delta Plus XP isotope ratio mass spectrometer (IRMS). The EA was calibrated with acetanilide (Costech Analytical Technologies Inc., Valencia, CA, USA) and caffeine (SigmalUltra; Wheaton Science Products, NJ, USA) reference standard materials; C and N were quantified using the IRMS. Typical instrumental precisions for POC and PON measurements were respectively, 0.2% and 0.4% of the measured concentrations.