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Calibration
Chilled Third Calibration Point
The chilled 3-point calibration is recommended if there is a large temperature variation during sampling or when
the temperature of the media cannot be anticipated. The highest concentration solution and one of the lower
concentration solutions should be at ambient temperature. The other lower concentration solution should be chilled to
less than 10°C to prior calibration point.
Preparing Standards
We recommend using YSI calibration solutions whenever possible. However, qualified users can follow these recipes to
prepare their own standards.
CAUTION:
Some of the chemicals required for these solutions could be hazardous under some conditions;
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
chemicals.
Ammonium Standards
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 equivalent amount of a less-hazardous, more dilute sample of the
acid may be used 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 NH
4
+
-N standard can be used in place of the solid ammonium
chloride.
1.
Discard the used standard and rinse the probe and calibration cup with a small amount of the next calibration
point standard. Discard the rinse standard.
2.
Fill the calibration cup to the appropriate level with fresh standard for the third calibration point. Immerse the
probe in the standard.
3.
Select
Calibration value
and enter the value of the third calibration standard.
4.
Observe the actual measurement readings for stability, and then select
Accept Calibration
. “Calibration
successful!” will be displayed in the message area.
