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Analytical Method: Ammonia (free) for Prove

Materials and reagents:
Cat.No. 173016 Spectroquant® VIS Spectrophotometer Prove 100 or
Cat.No. 173017  Spectroquant® UV/VIS Spectrophotometer Prove 300 or
Cat.No. 173018  Spectroquant® UV/VIS Spectrophotometer Prove 600

Cat.No. 114946 Rectangular cells 10 mm and/or
Cat.No. 114947 Rectangular cells 20 mm and/or
Cat.No. 114944 Rectangular cells 50 mm and/or
Cat.No. 173502 Semi-microcells 50 mm
Cat.No. 114752 Spectroquant® Ammonium Test

Cat.No. 116754  Water for analysis or distilled water
Cat.No. 109137  Sodium hydroxide solution 1 mol/l Titripur®
Cat.No. 109072  Sulfuric acid 0.5 mol/l Titripur®
pH-meter
Thermometer

 

Method:
Measurement of free ammonia under consideration of the pH and temperature of the sample after spectrophotometric determination of the ammonium content.
Evaluation acc. to Steffens (see the literature 1)).

 

Measuring range:
Method No. 2520

0.00 – 3.65 mg/l NH3        0.00 – 3.00 mg/l NH3-N       in the 10-mm rectangular cell

0.00 – 1.83 mg/l NH3        0.00 – 1.50 mg/l NH3-N       in the 20-mm rectangular cell

0.000 – 0.730 mg/l NH3    0.000 – 0.600 mg/l NH3-N   in the 50-mm rectangular cell

 

Working instructions:
Sample preparation:
Measure the original pH and make a note of the result.
Measure the original temperature of the sample and make a note of the result (0 – 60 °C).
Adjust the pH of the sample to be analyzed to 4 – 13.
If the pH is <4 add diluted sodium hydroxide solution dropwise, if the pH is >13 add diluted sulfuric acid dropwise until a pH value between 4 and 13 is achieved.
Temper the sample to be analyzed to a temperature of 20 – 30 °C.

 
Zero adjustment:
It is recommended to perform a zero adjustment for this method each new working day.
It is recommended to use the same cell for zero adjustment and for sample measurement.


Select method 2520 „Ammonia free“ from method list.
Prior to the zero adjustment enter and confirm the method parameters "pH" and "temperature".
In case of an expired zero adjustment the system automaticalley prompts a zero adjustment, otherwise press "Settings" and select “ZERO ADJUSTMENT” from selection list.
Fill a cell with distilled water (or water for analysis) and insert the cell into the cell shaft. The zero adjustment is executed automatically.
Confirm the implementation of zero adjustment with "OK".

 

Analysis:
The measurement is carried out according to the packaging insert of the above mentioned Spectroquant® Ammonium Test.
For measurement in the 50-mm cell both the sample volume as well as the quantities of reagents NH4-1, NH4-2, and NH4-3 must be doubled. Alternatively, the semi-microcell, Cat.No. 173502, can be used.

 

Measurement procedure
Select method 2520 "Ammonia, free" from method list.
Enter the pH value in the entry field "pH" and confirm with "OK".
Tip on entry field „Temperature”, enter the temperature in °C and confirm with "OK".
Press "START" to reach the measurement mode.
Perform a zero adjustment (procedure see “Zero adjustment”).
Fill a cell with the measurement sample and insert the cell into the cell shaft. The measurement is executed automatically.
Confirm measurement with "OK".
The results in mg/l NH3 and mg/l NH3-N appears on the display.

Press "START" to start the measurement procedure for the next sample.

 

Note:
The measurement solution should be yellow-green to green in color.
Very high concentrations of ammonium in the sample produce a turquoise coloration of the measurement solution and lead to false-low results. In such cases a plausibility check of the measurement results should be run by diluting the sample (1:10, 1:100) with distilled water or water for analysis.

 

Literature:
1. Steffens, W.: 1981: Moderne Fischwirtschaft – Grundlagen und Praxis;
Verlag J. Neumann-Neudamm, Melsungen, Germany

 

 

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