Stable Isotope Laboratory (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 L1102-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.
Instrumentation

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.

Picarro L1102-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.