Stable Isotope Lab (SIL)

Mission Statement and Philosophy

The Stable Isotope Laboratory (SIL) is intended to be a hands-on teaching and research facility for the students and faculty at Iowa State University. The laboratory is devoted to performing continuous-flow isotopic (‰) and elemental (%) analyses of carbon (C), nitrogen (N), oxygen (O) and hydrogen (H) in organic and inorganic substrates (solids, liquids, and gases). The lab supports research in different disciplines, including oceanography, paleoclimatology, geology, ecology, agronomy, and chemistry. In addition, analyses of samples for other interested researchers are also performed in the lab (see sample pricing).

The laboratory consists of a ThermoFinnigan Delta Plus XL mass spectrometer coupled with several sample introduction systems, including a GasBench II with a CombiPal autosampler, a Costech elemental analyzer and a TC/EA with a Conflo III interface. Additionally, the SIL operates a Picarro L2130-i Isotopic Liquid Water Analyzer with an autosampler for rapid measurements of deuterium and oxygen.

Micromilling Device and other Facilities

We have a fully operational micromilling device, which facilitates accurate, fine-scale, sampling of carbonate material. The Merchantek micromill with a Leica GZ6 microscope is capable of 20 micrometer sampling steps.

The laboratory houses a number of facilities intended to aid in the preparation and purification of samples for isotopic and elemental determinations. These facilities include a ballmill grinding device, a freeze-dryer, solvent-extraction apparatus, and vacuum glass lines.


ThermoFinnigan Delta Plus XL mass spectrometer coupled with a GasBench II with a CombiPal autosampler. The long-term precision of the mass spectrometer is ±0.09‰ for d18O and ±0.06‰ for d13C, respectively, and precision is not compromised with small carbonate samples (~150 micrograms).

The mass-spectrometer is configured for high-precision isotope ratio analyses of hydrogen, nitrogen, carbon, and oxygen. These analyses are performed on hydrogen, oxygen, nitrogen, and carbon monoxide and dioxide generated from biological and geological substrates. Peripheral devices attached to the Delta Plus XL allow rapid and automated generation of gases introduced into the mass-spectrometer for isotopic determinations.

These devices include:

A Costech Elemental Analyzer with zero-blank autosampler for the analyses of bulk organic carbon and nitrogen isotopes in plant materials, soils, sediments, and rocks.

A Gas Bench with a CombiPAL autosampler for the automated analyses of oxygen isotopes in water, carbon and oxygen isotopes in carbonates, and carbon isotopes in dissolved inorganic carbon. In addition, the device allows isotopic determinations of oxygen and carbon isotopes in atmospheric or purified carbon dioxide.

A TC/EA (thermochemical elemental analyzer) with zero-blank autosampler for the automated analyses of oxygen isotopes in nitrates, sulfates, and phosphates. This device also allows the determination of hydrogen isotopes in water and organic samples.

A Picarro L2130-i Isotopic Liquid Water Analyzer with autosampler. The analyzer operates using the technique commonly known as Wavelength Scanned Cavity Ringdown Spectroscopy (WS-CRDS). The precision of the WS-CRDS is ±0.5‰ for dD and ±0.10‰ for d18O respectively.