GB/T 18633-2018 English PDF (GBT18633-2018)

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GB/T 18633-2018: Determination of potassium in feeds -- Flame photometry
GB/T 18633-2018
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 65.120
B 46
Replacing GB/T 18633-2002
Determination of Potassium in Feeds -
Flame Photometry
ISSUED ON. MAY 14, 2018
IMPLEMENTED ON. DECEMBER 01, 2018
Issued by. State Administration for Market Regulation;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative References ... 4
3 Principles ... 4
4 Reagents and Materials ... 5
5 Instruments ... 5
6 Sampling and Specimen Preparation... 6
7 Analytical Procedures ... 6
8 Test Data Processing ... 7
9 Repeatability ... 7
Determination of Potassium in Feeds -
Flame Photometry
1 Scope
This Standard specifies using flame photometry to determine the potassium in the
feeds.
This Standard is applicable to determine the potassium in the feed ingredients, formula
feed, concentrated feed, concentrate supplement, and additive premix.
This Standard method’s detection limit is 2.00mg/kg; quantitative limit is 200mg/kg.
2 Normative References
The following documents are essential to the application of this document. For the
dated documents, only the versions with the dates indicated are applicable to this
document; for the undated documents, only the latest version (including all the
amendments) are applicable to this document.
GB/T 6682 Water for Laboratory Use – Specifications
GB/T 14699.1 Feeding Stuffs – Sampling
GB/T 20195 Animal Feeding Stuffs – Preparation of Test Samples
3 Principles
Dry ashing the feed ingredients, formula feed, concentrated feed, and concentrate
supplement; dissolve the residue under acidic conditions, make the constant volume
of specimen solution; use acid leaching method to treat the additive premix, make
constant volume of specimen solution; introduce the specimen solution into a flame
photometer; measure the emission intensity of potassium at the wavelength of
766.5nm after the flame atomization; compare with the emission intensity on
corresponding standard curve, then calculate the potassium content in the feed.
5.6 Centrifuge. with speed greater than 5000r/min.
5.7 Magnetic stirrer.
6 Sampling and Specimen Preparation
According to the provisions of GB/T 14699.1, take a representative feed sample; use
quadruple method to reduce the sample; then prepare the specimen according to GB/T
20195. Smash it till totally pass the 0.45mm sieve (4.7); mix evenly; store into the
sealed container for later-use.
7 Analytical Procedures
7.1 Extraction
7.1.1 Specimen treatment of feed ingredients, formula feed, concentrated feed
and concentrate supplement
Take about 1g~2g of specimen (accurate to 0.0001g); place into 50mL porcelain
crucible (5.3); carbonize with small fire on the temperature control electric furnace (5.4);
ash for 2h in 500°C high-temperature furnace (5.2); if there is still small amount of
carbon particles, drop nitric acid solution (4.2) to wet the residue; continue to ash in
the 500°C high-temperature furnace (5.2) till there is no carbon particles; take out and
cool off; drop small amount of water into the residue; wet it; then add 10mL of
hydrochloric acid solution (4.3); add water to 15mL; boil for 2min~3min, then cool off;
transfer into the appropriate volume of volumetric flask to make constant volume; filter
it; obtain the specimen solution for later-use. Meanwhile, prepare the blank solution of
specimen.
7.1.2 Additive premix specimen treatment
Take 1g~3g of specimen (accurate to 0.0001g); place into 250mL conical flask with
stopper; add 100.0mL of hydrochloric acid solution (4.4); stir and extract with magnetic
stirrer (5.7) for 30min; then use centrifuge (5.6) to perform centrifugal separation for
5min at the speed of 5000r/min; take the supernatant liquid as the specimen solution;
or after stirring and extraction, take the solution obtained by dry filtration as the
specimen solution; meanwhile, prepare the blank solution of the specimen.
7.2 Determination
Separately take appropriate amount of potassium standard working solution (4.6.3)
and specimen solution (7.1); introduce them into flame photometer (5.5); measure their
emission intensity at the wavelength of 766.5nm; meanwhile, measure the emission