GB/T 13086-2020Method for determination of free gossypol in feeds (English PDF)

8.2 of this Edition);

--- Modify the significant figures of measurement results (see Clause 8 of this Edition;

7.2 of 1991 Edition);

--- Modify the precision provisions (see Clause 9 of this Edition; 7.3 of 1991 Edition);

--- Add the informative Appendix A (see Appendix A of this Edition).

This Standard uses the redrafting method to modify and adopt the international

standard ISO 6866:1985 Animal Feed Stuffs - Determination of Free and Total

Gossypol.

Compared with ISO 6866:1985, this Standard has major adjustments in structure.

Appendix A lists the clause number comparison between this Standard and ISO

6866:1985.

The technical differences and causes between this Standard and ISO 6866:1985 are

as follows:

--- Regarding the normative references, this Standard adjusts the technical

differences to adapt to China's technical conditions. The adjusted conditions and

technologies are reflected in Clause 2 Normative Reference. The specific

adjustments are as follows:

 Delete the reference document ISO 6497 in ISO 6866:1985;

 Replace ISO 6498 by GB/T 20195 which is equivalent to adopting

international standard;

 Add reference of GB/T 6682.

--- The measurement wavelength of the absorbance value is changed from "the

wavelength of maximum absorption (435nm~445nm)" to "the wavelength of

440nm" (see Clause 3, 7.3 of this Edition; 8.3.1.8 of ISO 6866:1985);

--- Delete the content related to the determination of total gossypol (see 8.3.2 of

ISO 6866:1985);

--- Add the calculation formula of corrected absorbance [see Formula (1) of this

Edition];

--- Delete the related content of total gossypol calculation (see 9.1 of ISO

6866:1985);

--- Modify the calculation formula of free gossypol content in the sample [see

Formula (2) of this Edition; 9.1 of ISO 6866:1985];

--- Add the calculation formula for the results of free gossypol in cottonseed [see

Formula (3) of this Edition];

--- Delete the content of the test report (see Clause 10 of ISO 6866:1985).

This Standard also makes the following editorial modifications:

--- Modify the name of the standard; and delete the determination of total gossypol,

which is suitable for the purpose of sampling in China;

Please note that certain contents of this document may involve patents. The issuing

agency of this document is not responsible for identifying these patents.

Method of Determination of Free Gossypol in Feeds

4.1 Water: Class-II specified in GB/T 6682.

7.1 Extraction of sample solution

7.1.1 Sample weighing

Do two tests in parallel. The sample weights for different tests are as follows:

--- Cottonseed: weigh 1g of each cottonwool and cottonseed kernel shell, accurate to

0.0001g;

---Cottonseed meal: weigh 1g, accurate to 0.0001g;

--- Other samples: weigh 5g, accurate to 0.01g.

7.1.2 Extraction of free gossypol

The sample was placed in a 250mL triangular flask with stopper; add 20 pieces of glass

beads; accurately add 50mL of solvent A; and the mixture is shaken and extracted at

room temperature at 120 times/min for 1h. Filter by filter paper; and cover the funnel

by a watch glass during filtering. Discard 5mL of the initial filtrate; and collect all the

remaining filtrate into a 100mL triangular flask with stopper for later-use. For

cottonseed samples, cottonwool and cottonseed kernel shells shall be placed in

different triangular flasks; and the other operations are the same as above.

7.2 Preparation of sample solution

7.2.1 Use a pipette to accurately pipette two aliquots of filtrate (7.1.2) of 5mL~10mL

(each filtrate contains about 50µg~100µg of free gossypol); and place them in two

25mL brown volumetric flasks a and b, respectively. If it is less than 10mL, use solvent

A to make up to 10mL.

7.2.2 Dilute a to the mark with isopropanol-n-hexane mixed solution (4.3); shake up;

this solution is used as a reference solution for the sample measurement solution.

7.2.3 Use a pipette to transfer two 10 mL of portions of solvent A into two 25 mL brown

volumetric flasks a0 and b0.

7.2.4 Dilute a0 to the mark by isopropanol-n-hexane mixed solution (4.3); shake up;

this solution is used as a reference solution for the blank measurement solution.

7.2.5 Add 2.0 mL of aniline (4.2) to b and b0; heat it on a boiling water bath for 30min;

then take it out; cool to room temperature; use isopropanol-n-hexane mixed solution

(4.3) to make the constant volume; shake well; and stand at room temperature for 1h.

7.3 Determination

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