Analytical Method: Phosphorus (total) in fruit juice concentrates

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. 116754  Water for analysis
 
Sample preparation:
Weigh exactly approximately 1 g sample into a 400-ml beaker, add 5 ml sulfuric acid 95 - 97% and slowly evaporate on an electric plate until the solution becomes black. Allow to cool and then add Perhydrol® in 1-ml portions. Vigorous reaction accompanied with foaming will take place. Continue heating the mixture until the fume point is reached. If the solution becomes brown or black, add Perhydrol® until it again becomes colorless. In this example, approximately 10 ml Perhydrol® would be required for oxidation of the sample. Allow to cool, dilute with ca. 50 ml water for analysis in a volumetric flask, adjust to pH 5 - 7 with 14 - 15 ml sodium hydroxide solution 32 % using a pH-meter and make up to 1 l with water for analysis. Dilute this solution to 1 l in a volumetric flask.
 
Analysis:
Determine with the above mentioned test kits.
 
Calculation:
Phosphorus (total) content in mg/l P = analysis result in mg/l P x 1000
 
Procedural comparison:
For black currant juice concentrate, 1713 mg/kg were established, for orange juice concentrate 656 mg/kg and for lemon juice concentrate 561 mg/kg. These values showed good correlation with those established using the procedure prescribed in § 35 LMBG (German Foodstuffs Law), section 31-00-6.

Materials

     
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