GB 5009.249-2016Determination of sodium iron (III) ethylenediaminetetraacetate, trihydrate in iron fortified soy sauce (English PDF)

3.1 Reagents

3.1.1 Methanol (CH3OH).

3.1.2 Methanol (CH3OH). chromatographically pure.

3.1.3 Water solution of tetrabutylammonium hydroxide (C16H36N · OH) (40

g/100 mL).

3.1.4 Formic acid (HCOOH).

3.1.5 Formic acid solution (100 mL/L). PIPETTE 5 mL of formic acid; USE water to make its volume reach to 50 mL.

3.1.6 Aqueous methanol solution (3 + 1). TAKE 750 mL of methanol (3.1.1);

ADD 250 mL of water; MIX it uniformly.

3.1.7 Ferrous sodium ethylenediaminetetraacetate standard substance

(C10H12FeN2NaO8 · 3H2O). purity >= 99.0%.

3.2 Preparation of standard solution

3.2.1 Ferrous sodium ethylenediaminetetraacetate standard stock solution (2.0

mg/mL). WEIGH 0.05 g of ferrous sodium ethylenediaminetetraacetate standard substance (accurate to 0.0001 g); PLACE it in a 25 mL volumetric flask; USE water to dissolve it to make it reach to a certain volume. This solution shall be prepared in a brown volumetric flask, stored in a refrigerator in the dark, recommended for use within 15 days.

3.2.2 Ferrous sodium ethylenediaminetetraacetate standard intermediate

solution (100 µg/mL). USE the aqueous methanol solution (3.1.6) to make the volume of 2.5 mL of ferrous sodium ethylenediaminetetraacetate standard stock solution to 50 mL. This solution shall be prepared in a brown volumetric flask and stored in the refrigerator in the dark.

3.2.3 Ferrous sodium ethylenediaminetetraacetate standard working solution.

Respectively, PIPETTE 1.0 mL, 2.0 mL, 4.0 mL, 6.0 mL, 8.0 mL, 10.0 mL of ferrous sodium ethylenediaminetetraacetate standard intermediate solution in a 50.0 mL brown volumetric flask; USE water to make its volume reach to the mark. The concentration is 2.0 µg/mL, 4.0 µg/mL, 8.0 µg/mL, 12.0 µg/mL, 16.0

µg/mL, 20.0 µg/mL, which shall be prepared before use.

5.1 Preparation of sample solution

PIPETTE 2.50 mL of the uniformly-mixed specimen; PLACE it into a 50.0 mL brown volumetric flask; ADD aqueous methanol solution (3.1.6) to dilute it to the mark; SHAKE it uniformly. LET it be standing in the dark for 50 min; USE filter paper to filter it. PIPETTE 5.00 mL of filtrate; PLACE it into a 50 mL brown volumetric flask; USE water to dilute it to the mark; SHAKE it uniformly; USE

0.45 µm filter membrane to filter it, to obtain a sample solution, which is ready

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