Analytical Method: Nickel (total) in dairy products

Instruments 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 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. 114554  Spectroquant® Nickel Cell Test
Cat.No. 114785  Spectroquant® Nickel Test
Cat.No. 100731  Sulfuric acid 95 - 97 % for analysis
Cat.No. 107209  Hydrogen peroxide 30 % (Perhydrol®) for analysis
Cat.No. 105590  Sodium hydroxide solution 32 % for analysis
Cat.No. 116754  Water for analysis
 
Sample preparation:
Break up exactly 2 g of the original sample into small pieces and subsequently mix with 10 ml of sulfuric acid in a 400-ml glass beaker. Weakly heat the mixture on a hob in the fume cupboard. Carefully add portion by portion 10 ml of Perhydrol® to the mixture. After the reaction has finished (development of gas, strong foaming), heat until SO3 begins to develop. If the mixture turns brown or black in color, cool, add 10 ml of Perhydrol®, and reheat. Repeat this procedure as many times as are necessary to produce a clear, colorless solution. As a rule 30 to 40 ml of Perhydrol® is required for this procedure.
Completely boil off the superfluous Perhydrol®, cool the residue, dilute with a little water for analysis, and adjust the pH on apH-meter to a value of 6 - 7 with sodium hydroxide solution 32 %. Transfer the solution to a 200-ml volumetric flask and make up to the mark with water for analysis.
 
Analysis:
Determine with the above mentioned test kits
 
Calculation:
Nickel (total) content in mg/l Ni = analysis value in mg/l Ni x 100
 
References:
Official Compendium of Methods of Investigation acc. to para 35 LMBG (German Foodstuffs Act), subpara 03.00 - 17

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