Instrumentation

The Stable Isotope Laboratory houses two stable isotope ratio mass spectrometers (Nu Instruments, Perspective series). The instruments are configured for continuous flow operation mode. 

EA-IRMS

One of the SIRMS is connected to an elemental analyzer (EuroVector, model EA3028) and to a glassy carbon high temperature reactor (HEKAtech). The EA-IRMS system measures the bulk isotope ratios δ13C and δ15N in organic matter, and δ2H and δ18O in water.  For measurements of carbon and nitrogen, samples wrapped in tin/silver capsules are oxidized to produce CO2 and nitrogen oxides, followed by reduction to convert the latter into N2. The gases (CO2 and N2) are separated by a packed GC column inside the EA and fed into the SIRMS.Similarly, water samples are pyrolyzed by the high temperature reactor into CO and H2, separated by gas chromatography inside the EA, and then fed into the SIRMS for isotope ratio analysis.

EA-IRMS

GC-IRMS

A second SIRMS is connected to a gas chromatograph (Agilent, model 7890A) for compound specific isotope ratio analysis of δ13C and δ2H. The GC is interfaced with a dual ceramic tube furnace for oxidation and pyrolysis reactions. Depending on the type of capillary column equipped, the GC-IRMS system can be used for isotope ratio measurements of various organic compounds. A pneumatic Valco valve switches sample introduction into the SIRMS to either oxidation (δ13C measurements) or pyrolysis (δ2H measurements) mode.

GC-IRMS

GC

A stand-alone gas chromatograph (Agilent 7890A) is equipped with a flame ionization detector and a DB-1 capillary column (60m x 0.25mm x 0.25micron), which makes it suitable for qualitative and quantitative analysis of organic compounds with high carbon content. The instrument utilizes hydrogen as carrier gas, which results in more efficient separation.

GC