GB 31604.47-2023National food safety standard - Food contact materials and products - Determination of fluorescent substances in paper, paperboard and paper products (English PDF)

3.1 Reagents

3.2 Reagent preparation

3.2.1 Hydrochloric acid solution (1+9). Mix hydrochloric acid and water in a volume

ratio of 1.9.

3.3 Standard products

Fluorescent whitening agent 220 (C40H40N12O16S4Na4, referred to as C.I.220, CAS

number. 16470-24-9). the purity of >=95%, or a standard product with national

certification and a Reference Material Certificate.

3.4 Preparation of standard solution

3.5 Materials

3.5.1 Gauze.

3.5.2 Glass wool.

4.1 UV lamp. The wavelength is 365 nm and 254 nm.

4.2 Scissors.

4.3 Right-angled triangle.

4.4 Ultrasonic cleaner.

4.9 Analytical balance. The sensitivity is 1 mg and 0.1 mg, respectively.

4.10 Chicken heart bottle. 250 mL.

4.11 Erlenmeyer flask with stopper. 250 mL.

4.12 Glass funnel.

4.13 Glass watch glass.

4.14 Tray.

4.15 Centrifuge. The rotating speed is >=3500 r/min.

5.1 Sample preparation

5.1.1 Sample preparation for direct measurement of fluorescent substances

For food contact paper and cardboard, such as food packaging paper, candy paper, and

popsicle paper, use scissors and a right-angled triangle to cut it into a size of 10 cmx10

cm or 100 cm2.If the sample area is less than 100 cm2, then cut the samples of the same

batch at the same position so that the total area reaches 100 cm2.According to the above

operation, randomly sample from this batch of products and cut out 5 samples with an

area of 100 cm2 to be tested.

5.1.2 Sample preparation when confirmation of fluorescent substances is required

For samples that require confirmation testing, weigh 10 g (accurate to 1 mg) of the

sample, cut into paper scraps of approximately 5 mmx5 mm, and then crush them into

cotton wool with a high-speed pulverizer for later use.

5.2 Direct measurement of fluorescent substances and judgment of results

In a darkroom or dark box, place the 100 cm2 sample cut according to 5.1.1 about 20

cm below the UV light source, turn on the power switch of the UV lamp, select the

detection wavelengths of 254 nm and 365 nm respectively, and directly observe whether

fluorescence phenomenon appears on the sample.

5.3 Confirmation of fluorescent substances

5.3.1 Preparation of non-fluorescent gauze

Use scissors and a right-angled triangle to cut out several pieces of gauze about 5 cmx5

cm in size.

5.3.2 Preparation of standard control gauze

Weigh 2.0 g of the uniformly crushed blank sample prepared according to 5.1.2

(accurate to 1 mg) into a 250 mL Erlenmeyer flask, add 0.5 mL of standard working

solution (40.0 mg/L), then place in a dark place (the illumination is required to be less

than 20 lx), add 100 mL of alkaline extracting solution, and conduct ultrasonic

extraction at 50 °C for 40 minutes.

5.3.5 Confirmatory test for fluorescent substances

In a darkroom or dark box, place the watch glass containing the standard control gauze,

blank sample gauze, and two parallel sample gauze about 20 cm below the UV light

source, turn on the power switch of the UV lamp, then select the detection wavelength

of 254 nm and 365 nm respectively, and observe directly.

5.3.6 Determination of confirmation test results of fluorescent substances

At the two wavelengths of 254 nm and 365 nm, if there is no obvious fluorescence

phenomenon in the two parallel sample gauze (that is, no obvious blue or purple

fluorescence), the fluorescent substance in the sample is judged to be negative; if two

parallel sample gauze both have obvious fluorescence phenomenon, the fluorescent

substance in the sample is judged to be positive; if only one parallel sample gauze has

obvious fluorescence phenomenon, it is necessary to carry out the parallel test of two

samples again.

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