HomeChemical Analysis for Food and Beverage TestingAnalytical Method: Phosphorus (Total) in Dairy Products

Analytical Method: Phosphorus (Total) in Dairy Products

Photometric determination using the Phosphorus molybdenum blue method subsequent to acid mineralisation

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. 114543 Spectroquant® Phosphate Cell Test
Cat.No. 114729 Spectroquant® Phosphate Cell Test
Cat.No. 114848 Spectroquant® Phosphate 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 %
Cat.No. 109535 MColorpHastTM Universal Indicator strips pH 0 - 14
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 for analysis 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 the pH-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.
For determination of total phosphorus, dilute the solution again, pipette 2 ml into a 100-ml volumetric flask and make up to the mark with water for analysis.

Determine with the above mentioned test kits.

Phosphorus (total) content in mg/kg P = analysis result in mg/l P x 5

Literature reference:
Collection of official analysis procedures according to § 35, section 03.00-17 of the German Food Law.