Analytical Method: Analytical Quality Assurance, Standard for Monochloramine

Reagents for chlorine standard solution:
Cat.No. 100316  Hydrochloric acid 25 % for analysis
Cat.No. 105614  Sodium hypochlorite solution (6 - 14 % active chlorine)
Cat.No. 109147  Sodium thiosulfate solution 0.1 mol/l 0.1 N solution
Cat.No. 105043  Potassium iodide for analysis
Cat.No. 105445  Zinc iodide starch solution for analysis
Cat.No. 116754  Water for analysis
 
Preparation of a stock solution of free chlorine:
First prepare a 1:10 dilution using a sodium hypochlorite solution containing approx. 13 % of active chlorine. For this pipette 10 ml of sodium hypochlorite solution into a calibrated or conformity-checked 100-ml volumetric flask and then make up to the mark with distilled water.
 
Precise assay of the stock solution for free chlorine:
Pipette 10.0 ml of the stock solution into a 250-ml ground-glass-stoppered conical flask containing 60 ml of distilled water. Subsequently add to this solution 5 ml of hydrochloric acid 25 %. And 3 g of potassium iodide. Close the conical flask with the ground-glass stopper, mix thoroughly, and leave to stand for 5 min. Titrate the eliminated iodine with sodium thiosulfate solution 0.1 mol/l until a weakly yellow color emerges. Add 2 ml of zinc iodide starch solution and titrate from blue to colorless.
 
Calculation:
1 ml sodium thiosulfate solution = 3.55 mg free chlorine
 
Further investigational concentrations may be prepared from the stock solution prepared according to the procedure described above by diluting accordingly.
 
Preparation of a 100 mg/l chlorine standard solution:
Prepare a chlorine standard solution of 100 mg/l Cl2 by adding the quantity according the above calculated result and fill up with water. This 100 mg/l standard is necessary for the control of Monochloramine.
 
Stability of the chlorine standard solution:
When stored in a cool place (refrigerator), the stock solution remains stable for approx. one week. The diluted investigational solutions are stable for approx. 2 hours.
 
Reagents for ammonium standard solution:
119812  Ammonium standard solution Certipur®, 1000 mg/l NH4 = 777 mg/l NH4-N
116754  Water for analysis
 
Preparation of the ammonium standard solution:
Pipette 12.87 ml of the Ammonium standard solution Certipur® in a calibrated or conformity-checked 1000-ml volumetric flask and make up to the mark with distilled water. The stock solution prepared according to this procedure has a concentration of 10 mg/l NH4-N.
 
Preparation of the monochloramine standard solution:
Place 5.0 g of chlorine standard solution and 10.0 ml ammonium standard solution in a calibrated or conformity-checked 1000-ml volumetric flask and make up to the mark with distilled water. The solution prepared according to this procedure has a concentration of 5.00 mg/l Cl2  or 3.63 mg/l NH2Cl.
 
Stability:
The solution must be used immediately.
 

For use with test kits:

 

Measuring range
in mg/l

101632

Spectroquant® Monochloramine Test

0.050 - 10.00 Cl2
0.036 - 7.25 NH2Cl

 

 

 

 

Materials

     
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