Sample Preparation


Sample Submission

UC Davis Plant Sciences

Nitrate (NO3) in Water Sample Preparation

Appointments are required for the bacterial denitrifier preparation. Contact us prior to your sampling date, as we are often booked up to 3 months in advance.


Nitrate in water samples for bacterial denitrifier preparation by the SIF should be filtered (<0.45 micron pore, preferably 0.1 micron), stored frozen, and shipped frozen. Use 30-60 mL nitrate-free, freezable, wide-mouthed, screw-top containers. A minimum of 10 mL of water sample is required, with 20-30 mL preferred. Samples requiring extensive handling by the SIF (e.g., filtering) will be charged incidental fees per sample.


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, please allow the SIF to refer you to an analytical facility that can determine the concentration for you. Required concentration range is 2 μM to 1500 μM nitrate. Samples with missing or inaccurate nitrate concentrations will be charged for reruns and take longer to process.


The bacterial denitrifier method does not discriminate between nitrate (NO3-) and nitrite (NO2-) nitrogen. Samples expected to contain nitrite should be prepared according to Granger and Sigman (2009) prior to submission to the SIF.



Special Sample Types

For enriched samples / tracer experiments, please contact the SIF prior to your experiment.


The SIF no longer accepts customer-prepared nitrate in water samples. Due to the nature of bacterial denitrification preparation and analysis, we cannot offer appropriate quality assurance unless we prepare the samples (and standards) ourselves. For a more detailed description of the NO3- in water preparation method, please see the denitrifier articles in the references section.


We do accept KCl soil extracts and TDN digests. Please contact us for details and special requirements.


For ammonium, most of our clients diffuse from solution onto acidified discs. The resulting disc is then submitted and analyzed as a solid sample. For details on performing the diffusion method, please see Holmes, et al (1998) in the references section.


Recommended supplies for customer prepared NO3 headspace samples

Manufacturer / Part#



Restek / 24685

20mL, 23 x 75mm, 20mm Crimp, Flat Base, autosampler vials

Pack of 100

Restek / 21761

20mm Aluminum Seals w/PTFE/Gray Butyl Rubber Septa

Pack of 100



Manufacturer / Part#



Wheaton / 209545 Leak-Resistant Wide-Mouth HDPE Bottles, 30mL, Natural w/ cap

Case of 72

Wheaton / 209546 Leak-Resistant Wide-Mouth HDPE Bottles, 60mL, Natural w/ cap

Case of 72

Wheaton / 209626 Leak-Resistant Wide-Mouth HDPE Bottles, 60mL, Amber w/ cap

Case of 72



Freezing and Shipping Samples

At low temperatures, both polypropylene and polystyrene become brittle and are prone to cracking. Please use only polyethylene or polycarbonate containers. Make sure the containers are nitrate-free. Leave enough headspace to account for expansion during freezing, and pre-chill your samples in a refrigerator for the first 12-24 hours prior to freezing.

Once frozen, carefully pack small sets of samples in ziplock bags or small boxes with dividers. Pack these sets in a larger hard-walled cooler or Styrofoam insulated shipping kit with packing peanuts or bubble wrap. Make sure the samples are well cushioned on all sides, as loose bottles can break during shipping. Do not use foam-only coolers or cardboard-only boxes for the exterior shipping container; these containers will disintegrate due to condensation and hard impacts when tossed by couriers.

Keep the entire shipment frozen until time to ship. "Pre-chilling" your cooler will extend refrigeration time. We recommend blue ice blocks, cold packs, or ice blankets for packages sent by Overnight or 1-day delivery. Dry ice is advisable for delivery times exceeding 2 days. Pack about 15-20 pounds of dry ice for the first 24 hours of transit, plus an additional 5-10 pounds of dry ice for each additional day of transit. Fill any remaining “air space” in the cooler with newspaper or other filler to slow sublimation and protect against damage.

Ship your samples by the fastest available method to arrive at the SIF midweek (Tuesday through Thursday). If you would like your cooler returned, please include a prepaid shipping label.

We recommend saving a duplicate set of samples in case of sample loss, whether due to shipping loss or cracked vials.

Please complete and submit the online Analysis Order Form and Sample List for your samples. Include nitrate concentrations for all samples for bacterial denitrification preparation by the SIF. Samples with missing or inaccurate nitrate concentrations will be charged for reruns and take longer to process. Be sure to include a printed copy of both forms with your samples. The SIF uses these forms to track your samples and to contact you regarding sample receipt, data, and invoicing. For mixed analysis requests, you must complete a separate set of forms for each type of analysis.

Sample Storage and Retention by the SIF

The SIF will store your samples in the freezer. Due to limited freezer space, please ship your samples to arrive only 1 to 3 weeks prior to your appointment. The SIF will send an email reminder approximately 4 to 6 weeks prior to your appointment. After analysis and reruns are complete, samples will be stored by SIF for 2 months and then discarded. Please review your results during this 2-month window.




D. M. Sigman, K. L. Casciotti, M. Andreani, C. Barford, M. Galanter, and J. K. Böhlke. 2001. A bacterial method for the nitrogen isotopic analysis of nitrate in seawater and freshwater. Anal. Chem. 73: 4145-4153.

K. L. Casciotti, D. M. Sigman, M. Galanter Hastings, J. K. Böhlke, and A. Hilkert. 2002. Measurement of the oxygen isotopic composition of nitrate in seawater and freshwater using the denitrifier method. Anal. Chem. 74: 4905-4912.

J. Granger and D.M. Sigman. 2009. Removal of nitrite with sulfamic acid for nitrate N and O isotope analysis with the denitrifier method. Rapid Comm. Mass Spectrom. 23: 3753-3762.

R. M. Holmes, J. W. McClelland, D. M. Sigman, B. Fry, and B. J. Peterson. 1998. Measuring 15N-NH4+ in marine, estuarine, and fresh waters: An adaptation of the ammonia diffusion method for samples with low ammonium concentrations. Mar. Chem. 60: 235-243.

e-mail: | phone: 530-752-8100 | fax: 530-752-4361
UC Davis Stable Isotope Facility | Department of Plant Sciences
One Shields Avenue | Davis, California, 95616 | USA