AMMONIA User Manual
AMMONIA_User 9/09
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APPENDIX E
Standards Preparation for Sensor Calibration
Recommended Standard solutions
:
For pH
Use pH buffer solutions 7 and 10 for two point calibration. Remove pH sensor from its mount and
place in container holding buffer solution. Rinse sensor and container with distilled water
thoroughly before filling with second buffer solution.
For Temperature
A two point calibration can be achieved using an ice bath (32 deg. F) for the low point and a room
thermometer for the high point. The sensor should be removed from its mounting and allowed to
stabilize for several minutes before calibration at each value.
For Ammonia
Recommended Standard: Ricca Chemical Co. Cat. No. 615-32 Ammonia Standard
CAS No. 12125-02-9
1.00 ml = 1.00 mg NH
3
(1000 ppm NH
3
)
[1.00 ml = 822.4 ug N (822.4 ppm N)]
NH
4
Cl in water
Use the ammonium chloride standard solution above and make up standard solutions for two point
calibration.
To ensure proper operation and for the initial ammonia sensor calibration, prepare
two test solutions that differ in their ammonia concentration by at least a factor of 10. The
standards should be made up to cover the expected operation range. 2 ml of 10 mol caustic soda
should be added to each standard prior to calibration to elevate the pH >11 in order to convert any
ammonium to ammonia.
Preparation of the two required solutions for ammonia calibration
1. For stock 100.0 ppm ammonia solution
Pour 10 ml of the recommended NH
4
Cl (ammonium chloride) standard (1 mg = 1 ml = 1000 ppm NH
3
)
solution into a 100 ml graduated measuring flask partially filled with ammonia free distilled water, mix
slightly, and then fill up to the 100 ml mark with ammonia free distilled water. This is a 100.0 ppm NH
3
solution standard which can be used to prepare the actual calibration standards.
2. For 10-mol caustic soda solution
40g of NaOH (sodium hydroxide) are dissolved in about 80ml of ammonia-free distilled water, in a 100ml measuring
flask. The solution will become a little warm. When it has cooled down to 20°C, top up to 100ml with distilled water.