eutech-instruments ammonia gas Manuel D’Utilisation

Instruction Manual 

 

Ammonia Gas-sensing Electrode

 

 

5

 
Sodium hydroxide buffer must be added to standards and samples before measurement. When 10M 
NaOH is added, all standards and samples should be in the range of pH 11 to 14. In this range, all 
ammonium species are converted to ammonia. Adding the 10M NaOH adjusts the total level of 
dissolved species below 1M. If the total level is greater than 1M, the sample should be diluted 
before measurement. For further explanation, see the section entitled Effect of Dissolved Species. 
 

 
Measurement of ammonia can be expressed in units of moles/liter, ppm as nitrogen, ppm as 
ammonia, or other convenient concentration unit. Table 1 lists conversion units. 
 
    TABLE 1:  Concentration Unit Conversion Factors 
 

moles/liter ppm 

N  

ppm NH3 

 
   10-

2

 

 140.0 

  

170.0 

   10-

3

   

 14.0   

  17.0 

   10-

4

   

  1.4 

  

   1.7 

 

MEASUREMENT PROCEDURE 
 

 
Direct measurement is a simple procedure for measuring a large number of samples. A single meter 
reading is all that is required for each sample. The ionic strength of samples and standards should 
be made the same by adjustment with ISA for all ammonia solutions. The temperature of both 
sample solutions and standard solutions should be the same. 
 

 

1. 

By serial dilution, prepare three standard solutions from the 0.1M or 1,000 ppm stock 
standard. The resultant concentrations should be 10-

2

M, 10-

3

M, and 10-

4

M or 1,000, 100 

and 10 ppm ammonia standards. Add 1 ml of ISA per 100 ml of standard. Prepare 
standards with a composition similar to the samples if the samples have an ionic strength 
above 0.1M. 

 
2. 

Place the most dilute solution (10-

4

M or 10 ppm) on the magnetic stirrer and begin stirring 

at a constant rate. After assuring that the meter is in the mV mode, lower the electrode tip 
into the solution.  After the reading has stabilized, record the mV value.   

 
3. 

Place the mid-range solution (10-

3

M or 100 ppm) on the magnetic stirrer and begin stirring 

at a constant rate. After rinsing the electrode with distilled water, blot dry, and immerse the 
electrode tip in the solution. When the reading has stabilized, record the mV value. 

 
4. 

Place the most concentrated solution (10-

2

M or 1,000 ppm) on the magnetic stirrer and 

begin stirring at a constant rate. After rinsing the electrode with distilled water, blot dry, 
and immerse the electrode tip in the solution. When the reading has stabilized, record the 
mV value.