GB/T 6437-2018Determination of phosphorus in feeds—Spectrophotometry (English PDF)
饲料中总磷的测定 分光光度法
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Issued by
SAMR; SAC
Level / Type
National · Recommended
Issue date
September 17, 2018
Implementation date
April 1, 2019
Scope
GB/T 6437-2018 is the English-translated version of 饲料中总磷的测定 分光光度法.
GB/T 6437-2018 sets out the spectrophotometric method for determining total phosphorus in feeds. It applies to feed ingredients and feed products; with a 5 g sample made up to 100 mL, the detection limit is 20 mg/kg and the quantification limit 60 mg/kg.
The specimen is digested and its phosphorus forms a yellow vanadium molybdenum complex with ammonium vanadium molybdate under acidic conditions, whose absorbance is measured at 400 nm and compared with a standard series.
Three pretreatments are given: dry ashing at 550 °C, wet digestion with nitric and perchloric acid, and dissolution in hydrochloric acid for trace element premixes.
The standard also covers reagents, instruments, specimen preparation, calculation of results and precision. It replaces GB/T 6437-2002, was issued on 17 September 2018 and has applied since 1 April 2019.
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Document preview — GB/T 6437-2018
National Standard of the People's Republic of China
- ICS
- 65.120
- Classification
- B 46
- Replacing
- GB/T 6437-2002
Issued by: State Administration for Market Regulation; Standardization Administration of the PRC
Contents
- Foreword3
- 1 Scope4
- 2 Normative references4
- 3 Principle4
- 4 Reagents or materials5
- 5 Instruments and equipment5
- 6 Specimen preparation6
- 7 Analysis steps6
- 8 Test data processing7
- 9 Precision8
1 Scope
This Standard specifies the spectrophotometry for the determination of total phosphorus content in feeds.
This Standard applies to the determination of phosphorus in feed ingredients and feed products.
When the sampling volume is 5g and the volume is set to 100mL, the detection limit is 20mg/kg, and the quantification limit is 60mg/kg.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 601, Chemical reagent - Preparations of standard volumetric solutions
GB/T 602, Chemical reagent - Preparations of standard solutions for impurity
GB/T 603, Chemical reagent - Preparations of reagent solutions for use in test methods
GB/T 6682, Water for analytical laboratory use - Specification and test methods
GB/T 14699.1, Feeding stuffs - Sampling
GB/T 20195, Animal feeding stuffs - Preparation of test samples
3 Principle
The total phosphorus in the specimen is digested and formed yellow vanadium molybdenum yellow [(NH4)3PO4NH4VO3·16MoO3] complex with ammonium vanadium molybdate under acidic conditions. The absorbance value of vanadium molybdenum yellow is proportional to the concentration of total phosphorus. Measure the absorbance value of vanadium molybdenum yellow in the specimen solution at a wavelength of 400nm. Perform quantitative comparison with standard series.
6 Specimen preparation
Take representative feed samples according to GB/T 14699.1. Use the quartering method to reduce to about 200g. Prepare samples according to GB/T 20195. Pass through an analytical sieve with a pore size of 0.42mm after crushing. Mix well. Put it into a grinding bottle for later use.
7 Analysis steps
7.1 Specimen pretreatment
7.1.1 Dry ashing method
Weigh 2g~5g of specimen, accurate to 1mg. Put in a crucible. Carefully conduct carbonization on the electric stove. Put into a high temperature furnace. Burn at 550°C for 3h (or continue to measure the crude ash). Take out and cool. Add 10mL of hydrochloric acid solution (4.3) and a few drops of nitric acid (4.1). Carefully boil about 10min. Transfer to a 100mL volumetric flask after cooling. Add water to dilute to the scale mark. Shake well. It shall be the specimen solution.
7.1.2 Wet digestion method
Weigh 0.5g~5g of specimen, accurate to 1mg. Put it in a Kjeldahl flask. Add 30mL of nitric acid (4.1). Carefully heat and boil until the yellow smoke escapes. Slightly cool.
Add 10mL of perchloric acid (4.2). Continue to heat until perchloric acid emits white smoke (do not evaporate to dryness). The solution is basically colorless. Cool. Add 30mL of water. Heat it till it is boiling. After cooling, transfer to a 100mL volumetric flask with water and dilute to the scale mark. Shake well and it shall be the specimen solution.
7.1.3 Hydrochloric acid dissolution method (applicable to trace element premix)
Weigh 0.2g~1g of specimen, accurate to 1mg. Place in a 100mL beaker. Slowly add 10mL of hydrochloric acid solution (4.3). Make them all dissolved. Transfer to 100mL volumetric flask after cooling. Add water to dilute to the scale mark. Shake well and it shall be the specimen solution.
7.2 Preparation of phosphorus standard working solution
Accurately pipette 0mL, 1mL, 2mL, 5mL, 10mL, 15mL of phosphorus standard stock solution (4.4) into 50mL volumetric flasks (that is, the phosphorus content is 0µg, 50µg, 100µg, 250µg, 500µg, 750µg). Add 10mL of ammonium vanadium molybdate developer (4.5) to each volumetric flask. Use water to dilute to the scale mark. Shake well. Place it at room temperature for more than 10min. Take 0mL of phosphorus standard solution as reference. Use 1cm cuvette. Measure the absorbance of each […]
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This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — 15 pages — is available in the English PDF.
Referenced standards
Normative references
- GB/T 601Chemical Reagent - Preparations of Standard Volumetric Solutions
- GB/T 602Chemical reagent - Preparation of standard solutions for impurity determination
- GB/T 603Chemical reagent - Preparations of reagent solutions for use in test methods
- GB/T 6682Water for analytical laboratory use - Specification and test methods
- GB/T 14699.1Feeding stuffs -- Sampling
- GB/T 20195Animal feed - Preparation of test samples
Cited by
- GB/T 20193-2025Feed material - Bone meal, meat and bone meal
- GB/T 20807-2025Supplementary concentrate of sheep
- GB/T 22919.10-2024Aquatic feeds - Part 10: Formula feed for tilapia
- GB/T 22919.12-2024Aquatic feed - Part 12: Formula feed for crucian carp
- GB/T 22919.6-2024Aquatic feeds - Part 6: Formula feed for grouper
- GB/T 22919.8-2024Aquatic feeds - Part 8: Formula feed for basa catfish
Similar standards
Editions of GB/T 6437
| Edition | Title | Revision | Status |
|---|---|---|---|
| GB/T 6437-2018 | Determination of phosphorus in feeds—Spectrophotometry | current edition | Current |
| GB/T 6437-2002 | Determination of phosphorus in feeds—Spectrophotometry | previous edition | Superseded |
This page sells the current edition, GB/T 6437-2018. Earlier editions are listed for reference only.
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Related Standards
GB/T 14699.1-2005 — Feeding stuffs -- Sampling
GB/T 20195-2024 — Animal feed - Preparation of test samples
GB/T 601-2016 — Chemical Reagent - Preparations of Standard Volumetric Solutions
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