Rapid, automated analysis of 13C and 18O of CO2 in gas samples by continuous-flow, isotope ratio mass spectrometry (CAT#: STEM-ST-0043-LJX)

Introduction

A rapid automated method for isotopic analysis of 13C and 18O in CO2 has been developed. A variety of gas samples containing CO2 can be swept from serological tubes into a helium carrier flow; impurities are separated on a GC column so that a pure pulse of CO2 in He flows into the mass spectrometer. Isotopic ratio determinations are carried out as the pulse passes through the mass spectrometer, allowing a sample to be measured approximately every 4 min. A double, concentric needle-probe is used to flush the sample from the tube so that 100% sample recovery is achieved, maximizing sensitivity and preventing the possibility of fractionation. The precision of the technique, sigma(m-1), is better than 0.2% (0.0002 atom per cent excess) for 13C and 0.4% (0.83 p.p.m.) for 18O for 10 micromol of CO2 at natural abundance. Samples containing only atmospheric concentrations of CO2 can also be analyzed.

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Principle Applications Procedure Materials Notes Related Products

Principle

Isotope ratio mass spectrometry (IRMS) leverages magnetic sector mass spectrometry to enable high-precision measurement of the stable isotope content of a sample. Typical measurements target hydrogen, carbon, nitrogen, and oxygen analyses—although elements with masses up to and including sulfur can be measured. Solid, liquid, or gas phase samples are converted to simple gases then introduced to the IRMS. During analysis, an electron impact source ionizes sample-derived gas which is then accelerated down a flight tube, separated by mass, and quantified using a series of Faraday cups. The high precision of IRMS enables enumeration of even very small isotopic fractionation associated with physical, chemical, and biological transformations or natural abundance measurements.

Applications

For explaining the detailed molecular mechanisms behind biological processes
For understanding and quantifying nutrient and material exchanges between ecosystems
For providing ultra-precise stable isotope analyses
For understanding the geological history of the Earth
For food authenticity, forensic science, medical research and anti-doping testing

Procedure

1. Fill the reaction tube and install it, connect the gas path
2. Check for helium leaks
3. Heat up the reactor, wait for the reaction tube to burn stable, adjust the state of the equipment
4. Wrap the sample in a tin cup and test the sample
5. Store and process data

Materials

• Sample Type:
Gas samples

Notes

1.The approach is also valuable for quantifying the reactivity and progression of an applied stable isotope tracer to help determine reaction rates and final disposition of applied substrates.
2.IRMS offers a way of measuring isotopic variations with extremely high levels of accuracy. It can be used to detect isotope values of lighter elements with no issues, making it instrumental in the analysis of organic and natural samples.

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