YSI ProDSS - Manual (Page 50)

48
Calibration
Preparing nitrate standards
We recommend using YSI calibration solutions whenever possible. However, qualified users can save cost by following
these recipes for 1 and 100 mg/L nitrate standards. Other concentrations can be made by altering the amount of
potassium nitrate. All other concentrations should remain unchanged.
CAUTION: Some of these chemicals are hazardous and therefore, the standards should only be prepared by
qualified chemists in laboratories where proper safety precautions are possible. It is the responsibility
of the user to obtain and study the MSDS for each chemical and to follow the required instructions
with regard to handling and disposal of these materials.
You will need:
• Solid potassium nitrate or a certified 1000 mg/l NO
3
-N from a supplier
• Magnesium sulfate, high purity water
• A good quality analytical balance
• 1000 mL volumetric flask
• Accurate volumetric measuring devices for 100 mL, 10 mL and 1 mL of solution
• And 1000 mL glass or plastic storage vessels.
•
100 mg/L standard
1. Accurately weigh 0.7222 g of anhydrous potassium nitrate and transfer quantitatively into a 1000 mL volumetric
flask. Add 1.0 g of anhydrous magnesium sulfate to the flask.
2. Add approximately 500 mL of water to the flask. Swirl to dissolve all of the reagents, and then dilute to the
volumetric mark with distilled or deionized water.
3. Mix well by repeated inversion and then transfer the 100 mg/L standard to a storage bottle.
4. Rinse the flask extensively with water prior to its use in the preparation of the 1 mg/l standard. Alternatively, 100
mL of certified 1000 mg/L NO
3
-N standard can be used in place of the solid potassium nitrate.
1 mg/L standard
1. Accurately measure 10.0 mL of the above 100 mg/L standard solution into a 1000 mL volumetric flask. Add 1.0
g of anhydrous magnesium sulfate to the flask.
2. Add approximately 500 mL of distilled or deionized water. Swirl to dissolve the solid reagents, and then dilute
to the volumetric mark with water.
3. Mix well by repeated inversion and then transfer the 1 mg/L standard to a storage bottle.
NOTE: Recipes are given for 1 and 100 mg/L. Other concentrations can be made by altering the amount of
potassium nitrate. All other concentrations should remain unchanged.