Nitrate in Water

Introduction

The amount of nitrate in a water sample will be found by using the TesTab^® color comparison method.

Concepts

• Concentration of nitrate
• Parts per million
• Water testing

Background

Nitrates accumulate in water systems from decaying vegetation, the atmosphere, fertilizer used in agriculture, animal excrement and sewage. Unpolluted water generally has an overall nitrate level less than 4 parts per million. If the concentration of nitrates reaches more than 10 parts per million, water may be unfit to drink. Surface water high in nitrates causes the overgrowth of algae and other organisms that will foul the water found in our water sources. This overgrowth of algae is known as an algae bloom. Algae blooms deplete the water of oxygen and may even create “dead zones” where fish will no longer live.

High levels of nitrates in drinking water can lead to a condition known as methemoglobinemia or blue baby disease. Blue baby disease occurs when high levels of nitrates enter the digestive tract of infants. In some infants, bacteria converts excess nitrates into nitrite. Nitrites react with hemoglobin and decrease the amount of oxygen in an individual’s bloodstream. As the oxygen level is depleted, the infant gradually suffers from a lack of oxygen, which causes the skin of the infant to turn a blue color. Blue baby disease can become fatal if not treated.

Materials

Safety Precautions

Nitrate TesTabs^® contain chemicals that may irritate skin or be harmful if swallowed. The TesTab reagents used in this kit were designed with safety in mind. The single-use, foil-packaged TesTabs are easy to dispense. Store TesTabs in a cool, dry place and only open when ready to use the tablet. A single tablet, either alone or reacted with a sample, is a low health hazard; however, TesTabs should not be ingested. Wear chemical splash goggles and chemical-resistant gloves. Please review current Safety Data Sheets for additional safety, handling and disposal information.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. In the field, reacted samples may be poured into a container for later treatment. Reacted samples may be flushed down the drain with plenty of water according to Flinn Suggested Disposal Method #26b.

Procedure

1. Fill the water sample tube to the 5-mL line with the water sample.
2. Add one Nitrate Wide Range TesTab to the tube.
3. Cap the tube and mix until the tablet has dissolved.
4. Wait for five minutes.
5. Compare the color of the sample to the Nitrate color comparison chart.
6. Dispose of the reacted sample according to the instructor and rinse the water sample tube twice with the water sample for the next test.

Teacher Tips

• Enough materials are provided for 15 tests.

• It’s a good idea to collect several water samples from each site that is tested. It is also wise to test the samples within one hour of collection if possible.
• Nitrate Wide Range TesTabs contain zinc, which reduces nitrate to nitrite, and chromotropic acid, which reacts with the nitrite to form a pink color.
• A wait of five minutes is required for the overall reaction to take place.
• The range of the nitrate TesTabs is between 0 to 40 ppm.
• TesTabs are a vendor product of the LaMotte Company. MSDS are available through the manufacturer website.