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Measurement of 13C/12C of chloroacetic acids by gas chromatography/combustion/isotope ratio mass spectrometry (CAT#: STEM-ST-0038-LJX)

Introduction

This service uses gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) to measure the 13C/12C ratios of chloroacetic acids (CAAs). CAAs are a major class of environmental pollutants that are widely distributed throughout the world, often at relatively high concentrations, and are of concern due to their toxic effects, particularly on plants. The 13C/12C of CAA reagents was measured by IRMS subsequent to offline combustion. Aqueous solutions of these CAAs were derivatized to the corresponding methyl chloroacetates (MCAAs) with acidic methanol with a known isotopic composition, extracted into pentane, and analyzed by GC/C/IRMS. Measured 13C/12C ratios of derivatized MCAAs were in agreement with calculated values within 1 per thousand for monochloroacetic acid and trichloroacetic acid and within 2 per thousand for dichloroacetic acid, suggesting that methylation and other analytical methodology steps do not isotopically fractionate derivatized MCAAs. 13C/12C ratios of reagent CAAs from different sources had varying isotopic signatures suggesting differences in source carbon and/or production methods. Our results underscore the potential of stable isotopes to serve as tracers of environmental sources of CAAs.




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:
Chloroacetic acids

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.