Other methods for determination of sorbic acid and benzoic acid content in food

1.
Determination by high performance liquid chromatography (according to the second method of GB/T5009.
29-2003)
.

(1) Principle The sample is heated to remove carbon dioxide and ethanol , the pH is adjusted to near neutral, filtered, and then entered into a high performance liquid chromatograph.
After separation by reversed-phase chromatography, it is qualitative and quantitative based on retention time and peak area
.

(2) Reagent

① methanol : filtered through a filter (0.
5um)
.

②Dilute ammonia (1+1): Mix ammonia with equal volume of water
.

③Ammonium acetate solution (0.
02mol/L): Weigh 1.
54g of ammonium acetate , add water to 1000mL, dissolve, and filter through a 0.
45um filter membrane
.

④ Sodium bicarbonate solution (20g/L): Weigh 2g of sodium bicarbonate (superior grade), add water to 100mL, shake to dissolve
.

⑤ Benzoic acid standard stock solution: accurately weigh 0.
1000g of benzoic acid, add 5mL of sodium bicarbonate solution (20g/L), heat to dissolve, transfer to a 100mL volumetric flask, add water to make up to 100mL, the content of benzoic acid is 1mg/mL, As a stock solution
.

⑥Sorbic acid standard stock solution: accurately weigh 0.
1000g of sorbic acid, add 5mL of sodium bicarbonate solution (20g/L), heat to dissolve, transfer to a 100mL volumetric flask, add water to make up to 100mL, the content of sorbic acid is 1mg/mL, As a stock solution
.

⑦ Standard mixed use solution of benzoic acid and sorbic acid: Take 10.
0 mL each of the standard stock solutions of benzoic acid and sorbic acid, put them into a 100 mL volumetric flask, and add water to the mark
.

(3) Instrument high performance liquid chromatograph (with external detector)

(4) Operation steps

①Sample processing:

a.
Soda water: Weigh 5.
00～10.
0g sample, put it into a small beaker, stir at gentle temperature to remove carbon dioxide , adjust the pH to about 7 with ammonia water (1+1)
.

b.
Juices: Weigh 5.
00～10.
0g sample, adjust the pH to about 7 with ammonia water (1+1), add water to make the volume to an appropriate volume, centrifuge for precipitation, and filter the supernatant through a 0.
45um filter membrane
.

c.
Alcohol preparation: Weigh 10.
0g sample, put it into a small beaker, heat in a water bath to remove ethanol, adjust pH to about 7 with ammonia water (1+1), add water to a proper volume, and filter through a 0.
45um filter membrane
.

②Reference conditions of high performance liquid chromatography:

Color harmonic column: YWG-C ₁₈ 4.
6mm×250mm, 10um stainless steel column
.

Mobile phase: methanol: ammonium acetate solution (0.
02mol/L) (5:95)
.

Flow rate: 1mL/min
.

Injection volume: 10uL
.

Detector: UV detector, 230nm wavelength, 0.
2AUFS
.

③Determination: Qualitatively based on retention time and quantified by external standard peak area method
.

(5) Result calculation

Where x-the content of benzoic acid or sorbic acid in the sample, g/kg

m ₁ ——the mass of benzoic acid or sorbic acid in the injection volume, mg

V ₁ ——Total volume of sample diluent, mL

V ₂ ——Injection volume, mL

m ₂ ——the mass of the sample, g

The calculation result retains two significant digits
.

The absolute difference between two independent determination results obtained under repeatability conditions shall not exceed 10% of the arithmetic mean
.

(6) Tips

① This method is applicable to the determination of sorbic acid and benzoic acid in foods such as soy sauce, fruit juice, jam
.

② This method can simultaneously determine saccharin sodium
.

2.

(1) Principle After the sample is acidified, benzoic acid and sorbic acid are extracted with ether .

Where x-the content of benzoic acid or sorbic acid in the sample, g/kg

m ₁ —The mass of benzoic acid or sorbic acid in the sample solution for determination, mg

V ₁ ——The volume of ethanol added, mL

V ₂ ——The volume of the spotted sample during measurement, mL

m ₂ ——the mass of the sample, g

10——The volume of the ether extract in the measurement, mL

25——Total volume of sample ether extract, mL

(2) The main points suggest that this method can simultaneously determine the saccharin in jam and fruit juice

Related Links: Determination of Sorbic Acid and Benzoic Acid in Beverages (2)