Background

The element nitrogen makes up over 78% of the earth's atmosphere. Nitrogen exists as a triple bonded molecule that needs to be broken down or "fixed" to a usable form such as ammonia or nitrate. Fixation can occur by a few different means; for example, by the action of nitrogen fixing bacteria like Rhizobium. These bacteria are found on the root system of plants called legumes, a class of plants which included beans or peanuts. Fixation can also occur through man-made means or by a reaction caused by flashes of lightning.

The nitrogen cycle involves the uptake of nitrogen in various forms by autographs and its passage through the food chain. It also includes the return of nitrogen by means of animal urine that is rich in nitrogenous wastes, and by the decomposition of organic material. This decomposition is where nitrate is formed and then easily converted to the usable form, nitrite. Nitrite is an intermediate in the nitrogen cycle formed during the decomposition of organic matter and is readily oxidized to form nitrate. Nitriteforming bacteria convert ammonia under aerobic conditions to nitrites. Under anaerobic conditions, nitrogen fixing bacteria reduce nitrates to nitrites. Because nitrites easily oxidize to nitrates, they are rarely found in surface waters. In surface waters, the presence of nitrite can indicated partially decomposed organic matter, excessive discharge from a waste treatment facility of industrial pollution.

Nitrate contamination can also be caused by septic tanks, solid waste landfill leachate, agricultural activity, hazardous waste landfills, or leaking underground storage tanks. New regulations placed on construction of municipal solid waste landfills require the inclusion of a groundwater monitoring device which will help reduce future problems.

Agricultural runoff adds a good amount of nitrate to the environment because of the nitrogen based fertilizers used. Rainfall carries nitrogen through the soil which leaches into nearby water sources.

Nitrate in concentrations higher than normal can cause algal blooms, rapid growths of algae and other microbes. These blooms can devastate an aquatic environment by depleting its oxygen supply.

Nitrate contaminated drinking water poses a significant health threat to children. It can indirectly cause methemoglobenemia or "blue-baby" syndrome. A bacterium in the child's stomach can reduce nitrate to nitrite. Nitrite reduces the blood's capacity to carry oxygen; as a result, the child turns blue from the reduced amount of oxygen in his blood. Large amounts of nitrates ingested by humans may have serious or even fatal effects. Small, repeated doses may lead to general depression, headache and mental impairment.

Test Method

The Snap Test kit utilizes a colorimetric chemistry in which nitrate is reduced to nitrite by a modification of the standard cadmium reduction. The nitrite then diazotizes with a primary aromatic amine, and finally couples with another organic molecule to produce a highly colored azo dye.

The intensity of the color is proportional to the amount of nitrate-nitrogen in the sample. Results are expressed in ppm (mg/L) nitrate-nitrogen as NO3-N.

This test kit is useful for the range of 1-5ppm nitrate.

Cautions & Safety Information

The foil packs contain cadmium, which is harmful is swallowed or inhaled. Read MSDS (material safety data sheet) before performing this test procedure.

If this product is used as directed, the user will not come in contact with the chemical reagents. If contact does occur, flush skin or eyes with water. If swallowed, call a physician.

As an added precaution, we recommend that the user wear safety glasses when performing this test.

Dispose of used test ampoules as instructed in MSDS.

Test Procedure

1. Fill the sample cup to the 25mL mark with your water sample.

2. Empty the contents of one foil pack into the sample cup.

3. Place the cap on the sample cup and shake the cup vigorously for exactly three minutes. Note: Timing is an important factor. Follow the time instructions as closely as possible to ensure the best results.

4. Allow the sample to sit undisturbed for approximately 30 seconds. This allows any undissolved particles to settle.

5. Place the tapered tip of the test ampoule into one of the four depressions in the bottom of the sample cup. Snap the tip by squeezing the test ampoule toward the side of the cup. The sample will fill the ampoule and begin to mix with the reagent inside.

6. Remove the fluid filled ampoule from the sample cup. Mix the contents of the ampoule by inverting it several times, allowing the bubble to travel from end to end inside.

7. Wipe all the liquid from the exterior of the ampoule and wait 10 minutes.

8. Use the comparator to determine the level of nitrate-nitrogen in the sample. Note: To convert the results to ppm (mg/L) nitrate as NO3, multiply the test results by 4.4.