Nitrogen (Total) in Dairy Products

Prove InstrumentsPhotometric determination subsequent to acid mineralization with Sulfuric acid and Perhydrol®

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 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 nitrogen, dilute the solution again, pipette 5 ml into a 100-ml volumetric flask and make up to the mark with water for analysis.

Analysis

Determine with the below mentioned test kit.

Calculation

Nitrogen (total) content in g/kg N = analysis result in mg/l N x 2

Literature reference

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

Materials

     

Products 100613 and 114763 are not compatible with Move 100.