Parameter detection of potassium citrate as a food additive

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A. 1 Warning

Some test procedures specified in the test method may lead to hazardous situations. Operators should take appropriate safety and protective measures

A.2 General Provisions

The reagents and water used in this standard, unless otherwise specified, refer to analytical pure reagents and Grade III water as specified in GB/T6682.

. The standard titration solution, impurity determination standard solution, formulation, and product used in the test method shall be prepared in accordance with the provisions of GB/T601, GB/T602, and GB/T603 unless otherwise specified; Unless otherwise specified, all solutions used are aqueous solutions

A.3 Identification Test

A.3.1 Reagents and Materials

A.3.1.1 5% Hydrochloric Acid Solution: Measure 117mL of hydrochloric acid and dilute to 1000mL

A.3.1.2 5% sulfuric acid solution: Measure 29mL of sulfuric acid, slowly inject about 700mL of water, cool, and dilute to 1000mL

A.3.1.3; Mercury sulfate solution: Weigh 5g of mercury oxide, add 40mL of water, slowly add 20mL of concentrated sulfuric acid, stir while adding 40mL of water to dissolve

A.3.1.4; Potassium permanganate solution:

A.3.1.5 Pyridine acetic anhydride solution (3+1): Mix pyridine and acetic anhydride in a ratio of 3:1

A.3.2 Analysis Steps

A.3.2.1 Take a small amount of sample and place it in a 25mL crucible. Ignite it with a direct flame to slowly decompose, but do not produce caramel odor.

A.3.2.2 Take 2mL of the sample solution, add a few drops of sulfuric acid solution, heat to boiling, add a few drops of potassium permanganate solution, shake, and the purple will disappear; Add another drop of mercury sulfate solution to form a white precipitate

A.3.2.3 Take about 5mL of the sample solution, add about 5mL of pyridine acetic anhydride, shake, and generate a yellow to red or purple red solution

A.3.2.4 Take the platinum wire, wet it with hydrochloric acid, dip it in the sample, and burn it in a colorless flame. The flame shows a violet color

A.4; Determination of potassium citrate content (on a dry basis)

A.4.1 Reagents and materials

A.4.1.1  Standard titration solution of perchloric acid: c (HClO4)=0.1mol/L

A.4.1.2 Crystal violet indicator solution: 5g/L

A.4.1.3 Glacial acetic acid

A.4.2 Analysis Steps

Weigh 0.25g of the dried sample, accurate to 0.0002g, add 40mL of glacial acetic acid, slightly heat to dissolve, cool, add 2 drops of crystal violet indicator solution, and titrate with perchloric acid standard solution until the solution changes from purple to blue as the endpoint.

. Perform a blank test using the same method

A.4.3 Result Calculation

The mass fraction w1 of potassium citrate content (calculated on a dry basis) is calculated according to equation (A.1):

Where:

c - the concentration of perchloric acid standard titration solution, in moles per liter (mol/L)

V1- Volume of perchloric acid standard titration solution used for sample titration, in milliliters (mL)

V0- Volume of perchloric acid standard titration solution used for blank titration, in milliliters (mL)

M - Molar mass of potassium citrate, in grams per mole

m - Mass of the sample, in grams (g)

1000- Conversion coefficient

The experimental results shall be based on the arithmetic mean of the parallel measurement results. The absolute difference between two independent measurement results obtained under repeatability conditions shall not exceed 0.2%

A.5; The determination of sulfate shall be carried out in accordance with the provisions of GB6782, with 15mL of sulfate standard solution II added

A.6; The determination of oxalate was carried out in accordance with the provisions of GB6782. The preparation of oxalic acid standard solution II (0.05g/L) was to extract 20mL of oxalic acid standard solution I and dilute it with water to 100mL. Weigh 0.5g of the sample to the nearest 0.01g

 

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