GB/T 6437-2018 (GB/T6437-2018, GBT 6437-2018, GBT6437-2018)
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Determination of phosphorus in feeds -- Spectrophotometry
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GB/T 6437-2018
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Standards related to: GB/T 6437-2018
| Standard ID | GB/T 6437-2018 (GB/T6437-2018) | | Description (Translated English) | Determination of phosphorus in feeds -- Spectrophotometry | | Sector / Industry | National Standard (Recommended) | | Classification of Chinese Standard | B46 | | Classification of International Standard | 65.120 | | Word Count Estimation | 6,648 | | Date of Issue | 2018-09-17 | | Date of Implementation | 2019-04-01 | | Older Standard (superseded by this standard) | GB/T 6437-2002 | | Drafting Organization | Shanghai Veterinary Drug Feeding Institute | | Administrative Organization | National Feed Industry Standardization Technical Committee (SAC/TC 76) | | Proposing organization | National Feed Industry Standardization Technical Committee (SAC/TC 76) | | Issuing agency(ies) | State Administration of Markets and China National Standardization Administration | GB/T 6437-2018
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 65.120
B 46
Replacing GB/T 6437-2002
Determination of phosphorus in feeds - Spectrophotometry
ISSUED ON: SEPTEMBER 17, 2018
IMPLEMENTED ON: APRIL 01, 2019
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Principle ... 4
4 Reagents or materials ... 5
5 Instruments and equipment ... 5
6 Specimen preparation ... 6
7 Analysis steps ... 6
8 Test data processing ... 7
9 Precision ... 8
Determination of phosphorus in feeds - Spectrophotometry
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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