Nitrate/Nitrite 17O Guide
Nitrate + nitrite isotopes are measured by the denitrifier method, which consists of the conversion of aqueous nitrate and nitrite to gaseous nitrous oxide by Pseudomonas aureofaciens. Prior to analysis on an IRMS, the product nitrous oxide is broken down in a 875°C gold tube to nitrogen and oxygen gas. The oxygen gas is measured to obtain δ17O.
Sample Volume
- The calculator below specifies the amount of sample needed for a single measurement. We recommend sending enough sample for at least four measurements.
- Ideally, 200 nmol of the analyte is injected per measurement, but the measurement is possible down to 50 nmol with reduced precision.
- A sample concentration of at least 10 µM is required to analyze the sample.
- A maximum of 5.5 mL can be injected per meaurement.
- We recommend sending an excess of sample whenever possible.
- If your sample concentration is too low, it can be increased by pre-concentrating your sample. This consists of evaporating the sample and reconstituting it in a smaller volume of water. We will do this for an additional fee.
Notes and Tips
Sampling Guide (Link)
Preservation
Preservation
- The simplest preservation technique is to keep the samples frozen
- Base may be added if necessary, but must be neutralized before analysis
- Since this method requires bacterial conversion, poisoned samples cannot be analyze
- The nitrous oxide produced for our measurements will include any present nitrite and nitrate. Therefore, our reported isotope values will include both of these compounds.
- Nitrite can be removed for an additional fee
Relevant Publications
Kaiser et al. 2007 - 17O measurement by denitrifier method
Granger and Sigman 2009 - Nitrite removal
Granger and Sigman 2009 - Nitrite removal