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).
For δ15N and δ13C analyses, ~ 1 mg of samples were weighed into tin cups (Costech, 3×5 mm) for elemental analysis-isotope ratio mass spectrometry (EA-IRMS). The PAL-LTER krill were analyzed at VIMS on a Costech ECS 4010 CHNS-O Elemental Analyzer (EA) (Costech Analytical Technologies, Inc.) coupled to a Delta V Advantage Isotope Ratio Mass Spectrometer (IRMS) with a Conflo IV Interface (Thermo Electron North America, LLC).
All other phytoplankton and zooplankton samples were analyzed at the Stable Isotope Lab at UC Santa Cruz using a Carlo Erba EA 1108 EA coupled to a Thermo-Finnigan DeltaPlus XP IRMS referenced to AIR and V-PDB standards for N and C, respectively.