Nitrate Analysis by Bacterial Denitrification

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Sample types
SIRFER provides analysis of δ15N and δ18O of nitrate in water by bacterial denitrification method. SIRFER uses a Thermo Finnigan MAT 253 IRMS coupled with a Thermo Finnigan DN GasBench via Thermo Finnigan Conflo IV.

Sample Preparation
Samples for bacterial denitrifier method should be filtered (preferably by 0.2 micron filter), stored frozen, and shipped frozen. Use 200 mL nitrate-free, freezable, wide-mouthed, screw-top containers. A minimum of 100 mL of water sample is required. If freezing is not possible please acidify the samples by adding nitrate free HCl to pH2. If you acidify your samples please mention that to SIRFER manager.  Analysis rate will be doubled for any job containing less than 15 samples. 

Accurate nitrate concentrations are required for all samples. Please specify if your concentrations are NO3 vs. NO3-N, μM vs. mg/L, etc. If this information is not available, SIRFER can help to determine the nitrate concentration of the samples with a minimal charge . Required concentration range is 2 μM to 1000 μM NO3-N. Samples with missing or inaccurate nitrate concentrations will be charged for reruns and take longer to process.

Samples should be shipped to SIRFER as described here. A request for analysis and sample ID list should be emailed to us at the time of shipping.

Instrumentation
​Thermo Finnigan MAT 253
Thermo Finnigan DN GasBench 
Thermo Finnigan Conflo IV
​GC-TC PAL autosampler