Direct Isotope Dilution Mass Spectrometry (D-IDMS)

Most elements have multiple isotopes. This means that atoms of the same element can stably exist with a different number of neutrons in the nucleus. The isotopic ratio for every element is a fixed and defined amount, allowing us to know the natural isotopic ratio of any element we are testing.

Our experiments begin by introducing an isotopic spike (a known amount of analyte with an artificially manipulated isotope ratio) to the sample. We allow the isotopic spike and the sample to equilibrate, creating an isotopic ratio in this mixture that differs from both the natural artificial ratios. By running the mixture through the experiment, we detect both the amount of total analyte (of both isotopic forms), as well as the new isotopic ratio of the mixture.

Once we know the concentration and isotopic ratios of both the end mixture and the isotopic spike, as well as the natural isotopic ratio of the sample, we can definitively calculate the precise concentration of the analyte in the sample. This yields data that is more powerful and accurate than any other technology available in any industry.

Traditional mass spectrometry analyses can be broken down into three steps, which appear in black on the list below. Our patented process adds an additional two steps before and after the traditional process, which appear below in green.

  1. Spike Sample with Isotopes
  2. Sample Processing
  3. Separation (Chromatography)
  4. Mass Spectrometry
  5. Definitively Quantify Sample from Isotope Ratio

Direct Speciated Isotope Dilution Mass Spectrometry (D-SIDMS)

In addition to the ability to detect and quantify samples, we can quantify the species of samples. Many analytes exist in different species, or chemical forms, and can transition between those species during experimentation. Analytes transition into different species through oxidation, reduction, transformation, degradation, binding, or many other processes, in between sample collection and experimentation. However, when the sample is isotopically spiked at the time of collection, the isotopic spike undergoes all of the same changes through processing and experimentation.

Because we can track the changes in the isotopic spike, we can back-calculate the changes in the original sample. We have the only method to precisely quantify different species as they existed when they were collected, correcting for changes that occur after collection or during processing.

EPA Method 6800

AIT’s method has been adopted by the US government under the name EPA Method 6800. Because of the unparalleled accuracy and precision of this method, it is the only legally-defensible analytical quantification method. To find out more technical information about this method, we invite you to read more about EPA Method 6800.