GB 5009.34-2022National food safety standard - Determination of sulfur dioxide in foods (English PDF)

3.1 Reagents

3.1.1 Hydrogen peroxide (H2O2). 30%.

3.1.2 Absolute ethanol (C2H5OH).

3.1.3 Sodium Hydroxide (NaOH).

3.1.4 Methyl red (C15H15N3O2).

3.1.5 Hydrochloric acid (HCl) (rho20=1.19g/mL).

3.1.6 Nitrogen (purity >99.9%).

3.2 Reagent preparation

3.2.1 Hydrogen peroxide solution (3%). Measure 100mL of hydrogen peroxide of

which its mass fraction is 30%. Add water to dilute to 1000mL. Prepare it when it is

needed.

3.2.2 Hydrochloric acid solution (6mol/L). Measure 50mL of hydrochloric acid

(rho20=l.19g/mL). Pour slowly into 50mL of water. Stir while pouring.

3.2.3 Methyl red ethanol solution indicator (2.5g/L). Weigh 0.25g of methyl red

indicator. Dissolve in 100mL of absolute ethanol.

3.3 Preparation of standard solution

4.1 Glass nitrogen-filled steamer. 500mL or 1000mL. Equip it with electric heating

jacket, nitrogen source and gas flow meter, or equivalent steaming equipment. See

Annex A for the schematic diagram of the device.

4.2 Electronic balance. Resolution is 0.01g.

4.3 10mL semi-micro-burettes and 25mL burettes.

4.4 Grinder.

4.5 Tissue masher.

5.1 Specimen pretreatment

5.1.1 Liquid specimen

Take specimens of beer, wine, fruit wine, other fermented wine, prepared wine, and

beverages. The sampling volume shall be greater than 1L. For packaging specimens

such as bagged specimens and bottled specimens, at least 3 packages (same batch or

number) shall be collected. Put all liquids in one container. Mix well. Seal and mark for

testing.

5.1.2 Solid specimen

Take specimens of grain processed products, solid condiments, biscuits, potato products,

candy products (including chocolate and products), substitute tea, pickled vegetables,

dried vegetable products, edible mushroom products, other vegetable products, candied

fruit, dried fruit products, roasted seeds and nuts and nut products (baked, fried, other),

sugar, dried aquatic products, cooked animal aquatic products, edible starch, starch

products, starch sugar, non-fermented soy products, vegetables, fruits, seawater

products, raw and dried nuts and seeds.

5.1.3 Semi-fluid specimen

For packaging specimens such as bagged specimens and bottled specimens, at least 3

packages (same lot or number) need to be collected.

5.2 Specimen determination

Take 20g~100g of solid or semi-fluid specimen (to the nearest of 0.01g; the sampling

amount depends on the content). Take 20mL(g)~200mL(g) of liquid specimen. Place

the weighed specimen in the round bottom flask A in Figure A.1.Add 200mL~500mL

of water. Install the device. Turn on the switch of the reflux condenser to supply water

(condensate temperature < 15°C). Place the glass tube connected to the port E at the

upper end of the condenser tube at the bottom of the 100mL conical flask. Add 50mL

of 3% hydrogen peroxide solution to the conical flask as the absorption solution (the

end of the glass tube shall be below the liquid level of the absorption solution). Add 3

drops of 2.5g/L methyl red ethanol solution indicator to the absorption solution.

10.1 Reagents

10.1.1 Ammonium sulfamate (H6N2O3S).

10.1.2 Disodium EDTA (C10H14N2Na2O8).

10.1.3 Formaldehyde (CH2O). 36%~38%; there shall be no polymer (no precipitation

and no separation of the solution).

10.1.4 Potassium hydrogen phthalate (KHC8H4O4).

10.2 Reagent preparation

10.2.1 Sodium hydroxide solution (1.5mol/L). Weigh 6.0g of NaOH (3.1.3). Dissolve

in water and dilute to 100mL.

10.2.2 Disodium EDTA solution (0.05mol/L). Weigh 1.86g of disodium

ethylenediaminetetraacetate (abbreviated as EDTA-2Na). Dissolve in water and dilute

to 100mL.

10.2.5 Pararosaniline hydrochloride solution (0.5g/L). Measure 25.0mL of 2%

pararosaniline hydrochloride solution. Respectively add 30mL of phosphoric acid and

12mL of hydrochloric acid (3.1.5). Use water to dilute to 100mL. Shake well. Place for

24h for future use (store in an airtight seal away from light).

10.2.6 Ammonium sulfamate solution (3g/L). Weigh 0.30g of ammonium sulfamate

(H6N2O3S). Dissolve in water and dilute to 100mL.

10.3 Standard product

Sulfur dioxide standard solution (100µg/mL). With national certification and granted a

standard substance certificate.

10.4 Preparation of standard solution

Sulfur dioxide standard solution (10µg/mL). Accurately pipette 5.0mL of sulfur dioxide

standard solution (100µg/mL). Use formaldehyde buffer absorption solution to set

volume to 50mL. Prepare it when it is needed.

11.1 Glass nitrogen-filled distiller. 500mL or 1000mL, or equivalent steaming

equipment. See Annex A for the schematic diagram of the device.

11.2 UV-visible spectrophotometer.

12.1 Specimen preparation

Same with 5.1.

12.2 Specimen processing

12.2.1 Direct extraction method

Weigh about 10g of solid specimen (to the nearest of 0.01g). Add 100mL of

formaldehyde buffered absorption solution. Vibrate and soak for 2h. Filter. Take the

filtrate for testing. Conduct blank test at the same time.

12.3 Preparation of standard curve

Respectively and accurately measure 0.00mL, 0.20mL, 0.50mL, 1.00mL, 2.00mL,

3.00mL of sulfur dioxide standard solution (equivalent to 0.0µg, 2.0µg, 5.0µg, 10.0µg,

20.0µg, 30.0µg sulfur dioxide).

12.4 Determination of specimen solution

According to the sulfur dioxide content in the specimen, pipette 0.50mL~10.00mL of

specimen solution. Placed in a 25mL stoppered test tube. Follow the operation of 12.3

"Add formaldehyde buffer absorption solution to 10.00mL...". Conduct the blank test

at the same time.

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