Chester Tester Testing Hints

This helpful hints guide was developed for the many devoted volunteers, including some of our employees, who monitor the Chester River which flows into the northern Chesapeake Bay and runs close to our manufacturing facility in Chestertown, Maryland.

These hints involve the following tests:

	Dissolved Oxygen (LaMotte code 5860)
	pH
	Nitrate TesTabs® (LaMotte code 3354)
	Nitrate Cadmium Reduction method (LaMotte code 3615)
	Nitrate SMART2 Colorimeter Method (LaMotte code 3649-SC)
	Salinity (LaMotte code 7459-01)
	Turbidity (LaMotte code 7519)
	Turbidity Secchi Disk (LaMotte code 0171)

1. Fill test tubes with sample so that the curved surface of the water (meniscus) sits on the tube fill line.
2. Hold dropper bottles and pipettes vertically to dispense uniform drops.
3. Add a level spoonful of powder unless directed differently.
4. Follow instructions for waiting and mixing times. Test results are calibrated to these times and any variation will cause error in the results.
5. Mix by inverting the test tube so that the air bubble travels completely from one end of the tube to the other.
6. View comparators in outdoor, non-direct light when possible.
7. Scrub tubes with diluted detergent and a test tube brush after use. Rinse thoroughly and allow to air dry before storing. If it looks clean enough to eat out of, it’s clean enough to do a test in.
8. Avoid extremes of temperature and store test kits out of direct sunlight.
9. Estimate the test result if it falls between two values of a comparator.

Dissolved Oxygen - Code 5860

1. Be sure that there are no air bubbles in the sample. The presence of bubbles will introduce error.
2. Set the sample bottle on a paper towel when adding reagents. Hold bottles vertically. Reagents should sink to the bottom of the bottle and displace a small amount of sample which will cause the bottle to overflow slightly.
3. After adding the acid, the sample must be mixed until the precipitate and the reagent have totally dissolved. The amount of precipitate is proportional to the amount of oxygen in the sample. Failure to dissolve all of the precipitate will result in low test results. There may be algae or other particles in the water that will not dissolve but they will look different than the precipitate.
4. Never put unused titrant, left in the Titrator, back into the reagent bottle.

pH - Wide Range or Narrow Range

1. Run the Wide Range test to get a rough idea of the pH of the sample. Then run a narrow range test to determine the pH more accurately.
2. Make sure that you are using the correct combination of indicator and comparator. Many pH indicators look alike.

Nitrate – TesTabs®- Code 3354

1. Store tablets carefully. They are very sensitive to heat and moisture. Tablets that are soft and puffy have gotten wet and will not react properly. Tablets with expired expiration dates should be discarded.
2. Make sure that tablets are thoroughly disintegrated. Invert the tube slowly, allowing the air bubble to travel from one end of the tube to the other, to mix the contents.

Nitrate - Cadmium Reduction- Code 3615 and SMART2 colorimeter methods

1. Measure the volume of sample and Mixed Acid accurately.
2. Follow all waiting and mixing times carefully. Use a timer or a clock with a second hand.
3. Tap the spoon against the side of the bottle to level off the spoonful of Nitrate Reducing Reagent.
4. After adding the powder, invert the tube to mix, allowing the air bubble to travel from one end of the tube to the other.
5. Practice using the axial reader. The way you hold it to catch the light will become automatic.
6. For the axial reader method, don’t forget to take the caps off the tubes when they are in the axial reader. For the SMART2 colorimeter, make sure the tube is dry and free of smudges before putting it into the meter.

Salinity- Code 7459-01

1. Dispense the water sample from the Titrator carefully.
2. Add Salinity Titration Reagent B until the color of the sample goes from a creamy lemon yellow to a pinkish tan.
3. Never put unused titrant, left in the Titrator, back into the reagent bottle.

Turbidity - Kit - Code 7519

1. Do not view the test in direct sunlight.
2. Stir the solution in each tube right before comparing the cloudiness.
3. Shake the Standard Turbidity Reagent throughout the testing.
4. Measure the Standard Turbidity Reagent carefully.
5. Ignore the apparent color of the sample. Look only at the fuzziness of the target.

Turbidity - Secchi Disk

1. View the disk in the shadow of a dock or boat to avoid glare.
2. Add weight if the disk does not travel vertically through the water due to strong currents.