GB/T 5537-2008Inspection of grain and oils - Determination of phosphatide content (English PDF)

6.5

Sodium molybdate;

6.6

Hydrazine sulfate.

6.7 Potassium dihydrogen phosphate

Dry at 101°C for 2h before use.

6.8 2.5% sodium molybdate dilute sulfuric acid solution

Measure 140mL of concentrated sulfuric acid (6.4). Inject into 300mL of water. Cool to room temperature. Add 12.5g of sodium molybdate. After dissolving, use water to set volume to 500mL. Shake well. Leave it for 24h for future use.

6.9 0.015% hydrazine sulfate solution

Dissolve 0.15g of hydrazine sulfate (6.6) in 1L of water.

6.10 50% potassium hydroxide solution

Dissolve 50g of potassium hydroxide (6.3) in 50mL of water.

6.11

1:1 hydrochloric acid solution: Dissolve hydrochloric acid (6.1) in an equal volume of water.

6.12 Phosphate standard stock solution: Weigh 0.4387g of dry potassium

dihydrogen phosphate (6.7). Use water to dissolve, dilute and set volume to

1000mL. This solution contains 0.1mg/mL phosphorus.

6.13 Phosphate standard solution for standard curve: Use a pipette 10mL of

standard stock solution (6.12) to a 100mL volumetric flask. Add water to dilute and set volume. This solution contains 0.01mg/mL phosphorus.

7.1 Sampling

In accordance with GB/T 5524.

7.2 Specimen preparation

In accordance with GB/T 15687.

7.3 Drawing of standard curve

Take six colorimetric tubes (5.9) and turn them into six numbers: 0, 1, 2, 4, 6, and 8. According to the number order, respectively inject 0mL, 1mL, 2mL, 4mL,

6mL, 8mL of standard solution (6.13). Then according to the sequence, respectively add 10mL, 9mL, 8mL, 6mL, 4mL, 2mL of water. Then add 8 mL of hydrazine sulfate solution (6.9) and 2mL of sodium molybdate solution (6.8) into the six colorimetric tubes. Add stoppers. Shake 3~4 times. Remove stoppers.

Put the colorimetric tubes into a boiling water bath (5.5) and heat for 10min.

X - Phospholipid content, in milligrams per gram (mg/g);

P - Phosphorus content of the test solution checked by the standard curve, in milligrams (mg);

m - Specimen mass, in grams (g);

V1 - Diluted volume after the sample is ashed, in milliliters (mL);

V2 - Volume of the test solution taken during color comparison, in milliliters (mL);

26.31

- Number of milligrams of each milligram of phosphorus equivalent to phospholipids.

When the extinction value of the tested solution is greater than 0.8, it needs to appropriately reduce the volume of the tested solution, so as to ensure that the extinction value of the tested solution is below 0.8.

Each sample shall be tested twice in parallel. When the result of parallel test meets the precision requirements, take its arithmetic mean as the result. The calculation result keeps three decimal places.