YSI ProDSS - Manual (Page 51)

49
Calibration
Preparing ammonium 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 standards. Other concentrations can be made by altering the amount of ammonium
chloride. All other ingredient 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 ammonium chloride or a certified 100 mg/L NH
4
+ -N from a supplier
• Lithium acetate dihydrate
• Concentrated hydrochloric acid
• High purity water
• A good quality analytical balance
• A 1000 mL volumetric flask
• Accurate volumetric measuring devices for 100 mL and 10 mL of solution
• And a 1000 mL glass or plastic storage vessels.
CAUTION: Hydrochloric acid is highly corrosive and toxic and should therefore be handled with extreme care
in a well-ventilated fume hood. The user could also add the equivalent amount of a less-hazardous,
more dilute sample of the acid if preferred.)
100 mg/L Standard
1. Accurately weigh 0.3817 g of ammonium chloride and transfer quantitatively into a 1000 mL volumetric flask.
Add 2.6 g of lithium acetate dihydrate to the flask.
2. Add approximately 500 mL of distilled or deionized 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. Add 3 drops of concentrated hydrochloric acid to the bottle, then seal and agitate to assure homogeneity.
Alternatively, 100 mL of certified 100 mg/L NH4+-N standard can be used in place of the solid ammonium
chloride.
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 2.6
g of lithium acetate dihydrate 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.
4. Add 3 drops of concentrated hydrochloric acid to the bottle, then seal and agitate to assure homogeneity.