Nitrate (NO₃^-) in Water Tips

1) Please contact the SIF prior to the collection, preparation, and/or shipment of water samples for bacterial denitrification assay. Failure to do so may result in delays in excess of 6 months, unsuccessful analysis, and/or loss of your water samples.

2) Highly acidic and highly alkaline samples can affect the denitrifying bacteria. Preservatives and poisons that halt biological activity will also affect the denitrifying bacteria. Instead, filter samples and freeze immediately.

3) Accurate nitrate concentrations (minimum 4 μM) are required for all samples. Please specify if your concentrations are NO₃^- vs. NO₃^--N, μM vs. mg/L, etc.

4) The bacterial denitrifier method does not discriminate between nitrate (NO₃^-) and nitrite (NO₂^-). Samples should be treated for nitrite removal according to Granger and Sigman (2009) prior to submission to the SIF.

5) We accept KCl soil extracts, TDN digests, and NH₄⁺ digests. Please contact us for details and special requirements.

6) For ammonium, most of our clients diffuse from solution onto acidified discs. The resulting disc is then submitted and analyzed as a solid sample. As of 2019, we are accepting a limited number of projects to test diffusion preparation as an SIF Service.

7) Enriched samples / tracer experiments - please contact the SIF prior to your experiment.

8) Considerations for Freezing Samples: At low temperatures, both polypropylene and polystyrene become brittle and 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; we recommend pre-chilling your samples in a refrigerator for the first 12-24 hours prior to freezing.

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

9) Shipping Tips for Frozen Water Samples

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; such 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 void 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 and note the request on your Analysis Order Form.