1 Scope
This standard specifies determination of phosphorus content in foods by spectrophotometric method.
Method I and Method II of this standard are applicable to determination of total phosphorus in foods; Method III is applicable to determination of compound phosphate in Western cooked and smoked ham (by phosphate).
Detection limit of Method I and Method II is both 2μg; linear range: 5 μg~50 μg for Method I - spectrophotometric method; 2 μg~10 μg for Method II - molecular absorption spectrophotometric method.
Method I Spectrophotometric Method
2 Principle
Organic substances in foods are oxidized by acid to make phosphorus combined with ammonium molybdate under acidic conditions to generate ammonium phosphomolybdate. Such compound is reduced by hydroquinone and sodium sulfite to a kind of blue compound - molybdenum blue. Spectrophotometer is used to measure the light absorption value of molybdenum blue at a wavelength of 660 nm, so as to conduct quantitative analysis of phosphorus content.
3 Reagents
3.1 Sulfuric acid: relative density, 1.84.
3.2 Perchloric acid - nitric acid digestive solution: 1+4 mixed solution.
Standard
GB/T 5009.87-2003 Determination of phosphorus in foods (English Version)
1 Scope
This standard specifies determination of phosphorus content in foods by spectrophotometric method.
Method I and Method II of this standard are applicable to determination of total phosphorus in foods; Method III is applicable to determination of compound phosphate in Western cooked and smoked ham (by phosphate).
Detection limit of Method I and Method II is both 2μg; linear range: 5 μg~50 μg for Method I - spectrophotometric method; 2 μg~10 μg for Method II - molecular absorption spectrophotometric method.
Method I Spectrophotometric Method
2 Principle
Organic substances in foods are oxidized by acid to make phosphorus combined with ammonium molybdate under acidic conditions to generate ammonium phosphomolybdate. Such compound is reduced by hydroquinone and sodium sulfite to a kind of blue compound - molybdenum blue. Spectrophotometer is used to measure the light absorption value of molybdenum blue at a wavelength of 660 nm, so as to conduct quantitative analysis of phosphorus content.
3 Reagents
3.1 Sulfuric acid: relative density, 1.84.
3.2 Perchloric acid - nitric acid digestive solution: 1+4 mixed solution.
