CONTINOUS FLOW ISOTOPE RATIO MASS SPECTROMETRY
For Measuring Isotope Ratios of C, N, O in Various Biological Materials
NSERC-IRC Program, University of Victoria
Isotope Ration Mass Spectrometry (IRMS)
IRMS Process Schematic
Atoms of the same atomic number but different atomic weights are called
isotopes. Most elements of biological interest (including C, H, O, N, and S) have
two or more stable isotopes, with the lightest of these present in much greater
abundance than the others. Each has a heavy isotope (13C and 15N) with a
natural abundance of ~1% or less and a light isotope (l2C and 14N) that makes up
all of the remainder, in the case of nitrogen, or virtually all in the case of carbon.
Studies examining stable isotopes at or near natural abundance levels are
usually reported as delta, a value given in parts per thousand or per mil ("o/oo").
Delta values are not absolute isotope abundances but differences between
sample readings and one or another of the widely used natural abundance
standards which are considered delta = zero. Absolute isotope ratios (R) are
measured for sample and standard, and the relative measure delta is calculated.
IRMS Capabilities
The Delta Advantage is a continous flow Mass Spectrometer fitted with two peripheral systems the Costech Elemental
Analyzer (EA) and Finnigan Gas Bench coupled with a Combipal Autosampler.
The EA eliminates the need for offline extraction reducing the analyses time to 6 minutes for C and N thus greatly
improving sample throughput.
Biological materials analyzed for stable isotope content include leaves, roots, soil, sediment, zooplankton, filters, plasma
and other solid and liquid substances.
An ideal sample intended for natural abundance isotopic analysis would contain 200 micrograms total N and 800
micrograms total C. It may not, of course, be possible to provide both these ideal amounts in one sample. The lower limits
for reliable day-to-day operation of our instrument at natural abundance isotope levels appear to be ~25 micrograms total
N and ~200 micrograms total C.
The Gas Bench facilitates the measurement of O18 and C13 in as little as 5 ml of water as well as C13 in DIC. The
Combipal Autosampler is fully automated and capable of analysing up to 90 samples per day.
APPLICATIONS
Among stable isotopes the most useful as biological tracers are the heavy isotopes of carbon and nitrogen. These two elements are found in the
earth, the atmosphere, and all living things.
Delta C13
Delta N15
•Useful tool in determining algal productivity in water bodies
Source of nutrients in lakes (marine, farm and industrial effluent, sewage)
•Source of carbon in lakes and reservoirs (terrestrial, etc)
Food web structure (source of food in fish communities)
•In sediments allows for paleoclimatic reconstruction
Food chain length and contaminant (mercury) concentration
Nitrogen cycling
Delta O18
Migration studies for birds, fish, zooplankton
Paleoclimatological record derived by looking at O18 and C13 of carbon Marine-freshwater linkages through spawning salmon
and oxygen bearing inorganic and organic matter in lake sediments
Reconstruction of historic salmon returns (especially sockeye).
Modeling productivity of freshwater systems
Contact:
Dr. Sergei Verenitch
NSERC-IRC Program
Water and Watershed Research
University of Victoria
Victoria, B.C. V8W 3N5 Canada
Phone: 250-721-6150
Fax: 250-721-7120
Website: www.uvic.ca/water