Analytical Method: Chromium (total) in effluents

Instruments, Reagents and Accessories:

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 or

Cat.No. 109748  Spectroquant® Photometer NOVA 30 or

Cat.No. 109751  Spectroquant® Photometer NOVA 60 or

Cat.No. 173632  Spectroquant® Colorimeter Move 100

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
Cat.No. 109137  Sodium hydroxide solution 1 mol/l
Cat.No. 109072  Sulfuric acid 0.5 mol/l
Cat.No. 109535  MColorpHastTM Universal indicator strips pH 0 - 14
Thermoreactor with 120 °C digestion temperature
 
Variant 1:
Cat.No. 114552  Spectroquant® Chromium Cell Test
Cat.No. 114724  Empty round cells incl. screw caps
 
Variant 2:
Cat.No. 114758  Spectroquant® Chromium Test
Cat.No. 114688  Crack Set 10C
 
Variant 3:
Cat.No. 114758  Spectroquant® Chromium Test
Cat.No. 114687  Crack Set 10
Cat.No. 114724  Empty round cells incl. screw caps
 
Hints:
Sewage water containing complexing agents like EDTA or Cyanide must be digested with potassium peroxodisulfate (= K2S2O8). Digestion frees the Cr3+ from these complexes. When the COD concentration is
> 300 mg/l to 500 mg/l double the quantity of potassium peroxodisulfate.
 
The pH of the sample must be within the range 5 - 8 before starting the digestion procedure. Adjust, if necessary, with sodium hydroxide solution or sulfuric acid.
 
Sample preparation using Variant 1:
Pipette 10 ml pretreated sample into an empty cell. Add 1 drop reagent Cr-1K and mix. Add 1 dose reagent Cr-2K (= K2S2O8), close the cell tightly, and mix. Heat the cell at 120 °C in the preheated thermoreactor for 60 min. Allow the closed cell to cool to room temperature in a test-tube rack. Do not cool with cold water! Check the pH of the solution with universal indicator strips. Adjust the pH with sodium hydroxide solution or sulfuric acid within the range 1 - 9.
 
Sample preparation using Variant 2:
Pipette 10 ml pretreated sample into a digestion cell. Add 1 dose reagent R-1K (= K2S2O8), close the cell tightly, and mix. Heat the cell at 120 °C in the preheated thermoreactor for 60 min.
Allow the closed cell to cool to room temperature in the cell rack. Do not cool with cold water! Add 3 drops of reagent R-2K to the cool cell and mix. Check the pH of the solution with universal indicator strips. Adjust the pH with sodium hydroxide solution or sulfuric acid within the range 1 - 9.
 
Sample preparation using Variant 3:
Pipette 10 ml pretreated sample into an empty cell. Add 1 drop reagent R-1 and mix. Add 1 dose reagent R-2
(= K2S2O8), close the cell tightly, and mix. Heat the cell at 120 °C in the preheated thermoreactor for 1 hour.
Allow the closed cell to cool to room temperature in the cell rack. Do not cool with cold water! Add 3 drops reagent R-3 to the cool cell and mix. Check the pH of the solution with universal indicator strips. Adjust the pH with sodium hydroxide solution or sulfuric acid within the range1 - 9.
 
Analyse: Determine with the above mentioned test kits
 
Calculation: Chromium (total) content in mg/l Cr = analysis value in mg/l Cr

Materials

     
Related Links