Nitrate Source Tracking – Sample Types and Selection

The following recommendations are general guidelines. Individual sample size requirements largely vary based on the material and concentration of nitrates (NO3). Isobar does not report nitrate concentration. Contact us for advice if you are concerned that your samples are too small. Note: Isobar can only accept samples submitted in batches of 20 samples minimum. 


Please use a box with sufficient packing to prevent breakage while in transit. We recommend commercial courier or ​registered ​first-class mail when sending the samples to the lab. Please email the courier and tracking number so we can monitor your package.

Always choose the best samples for your research objectives



Small vial*
Nalgene bottles**


Before placing the water bottles in a sturdy cardboard box, please put them inside a plastic bag and seal the bag with a zip-tie or duct tape. If any of the bottles leak during shipment, the water will not weaken the box.

Please take note of the following features:
(1) Water type: (a) river, creek, stream, (b) lake, pond, pool, marsh, (c) ocean, sea, saltwater lake, (d) groundwater well, (e) snow, ice, snow cores, (f) rain, (g) soil or vadose-zone water
(2) Stabilization: (a) Yes, stabilized with preserved vial, (b) Yes, by adding hydrochloric acid, (c) No, not stabilized***
(3) Filtration: (a) ≤ 0.2 μm, (b) > 0.2 μm and < 0.5 μm, (c) ≥ 0.5 μm and < 1.0 μm, (d) ≥ 1.0 μm, (e) not filtered
(4) Salinity (PSU): (a) ≤ 10, (b) > 10 and ≤ 20, (c) >20 and ≤ 40, (d) >40***, (e) Unknown

We accept:
• Groundwater, saltwater, rain, snow, vadose-zone water, and stormwater
• Samples up to 35 PSU (the standard salinity of seawater)

We do not accept: 
• Water samples that have been collected from any area that is near to a nuclear power plant, commercial or medical reactors, industrial/medical waste disposal sites or from within their drainage areas as it could contaminate the sample with: (1) artificial 14C or (2) any other isotope that have been manipulated from the natural levels (e.g. enriched, labeled, depleted).
• Samples stored or handled in any laboratory or area that uses OR has ever used biomedical or artificially labeled 14C material OR any isotope that has been manipulated from the natural levels at any time.
• Seawater samples that have been treated with mercuric chloride (HgCl2) or sodium azide (NaN3).
• Water that has NaOH or other alkali chemicals added to the sample.

• We cannot accept unstabilized samples or samples with a Salinity >40 for analysis at this time.

* Use a small plastic vial with no prior use and fill to the top with no headspace. Isobar does not accept water samples for stable isotope analysis that still need to be pretreated (send filtered samples with no chemicals added).

** Please DO NOT use glass bottles, recycled drinking water bottles, or other lightweight / low-density plastic bottles as they may allow isotopic effects to take place and bias the measurements, causing inaccuracies in the reported results. We accept no responsibility for the accuracy of testing results for samples submitted in collection bottles other than those specified.

*** We cannot accept unstabilized samples or samples with a Salinity >40 for analysis at this time

Values represent the ideal sample characteristics, however, other options are still acceptable for analysis

If you plan to use the boron isotope service in conjunction with the nitrate, make sure to collect an individual non-acidified sample in a separate 100 mL plastic container.

Download NST Sampling Guide

Please fill out the form to download our Nitrate Source Tracking sampling guide.