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This standard replaces the fluorescent substance detection part of GB/T 5009.78-2003 Method for Analysis of Hygienic Standard of Papers for Food Packaging and SN/T 2901-2011 Imported and Exported Food Contact Materials - Determination of Flourescent Brightener in Paper and Paper Products - Liquid Phase Chromatography.
The following main changes have been made with respect to GB/T 5009.78-2003 (the previous edition):
——the standard is renamed as National Food Safety Standard - Food Contact Materials and Articles - Determination of Flourescent Brightener in Paper, Paper boards and Paper Products;
——the confirmatory test is added;
——the application scope is added.
National Food Safety Standard
Food Contact Materials and Articles - Determination of Flourescent Brightener in Paper, Paper Boards and Paper Products
1 Scope
This Standard specifies methods of determination for flourescent brightener in paper, paper boards and paper products for food.
This Standard is applicable to determination for flourescent brightener in paper, paper boards and paper products for food.
2 Principle
After flourescent brightener absorbs black light (with wavelength of 300 nm ~ 400 nm), the electrons in flourescent brightener molecules transit from the ground state, and back to the ground state in an extremely short time, transmitting blue or violet fluorescence (with wavelength of 420 nm ~ 480 nm). Therefore, by observing the specimen under 365nm ultraviolet lamp whether there is an obvious fluorescence phenomenon, carry out the qualitative determination for flourescent brightener in specimen or not. If the specimen shows multiple discontinuous fleck fluorescence or has fluorescence phenomena but obscure, extract with alkali extract, adjust the extract to be acid; with gauze, adsorb flourescent brightener in the extract; observe the gauze under 365 nm ultraviolet lamp and confirm whether there is flourescent brightener in the specimen.
3 Reagents and Materials
Unless otherwise specified, analytically-pure reagents and Class-I water (defined in GB/T 6682) are adopted for the purpose of this method. All reagents and materials under ultraviolet lamp shall show no fluorescence.
3.1 Reagents
3.1.1 Acetonitrile (CH3CN): chromatographically pure.
3.1.2 Triethylamine [(CH3CH2)3N].
3.1.3 Sodium hydrate (NaOH): guaranteed reagent.
3.1.4 Hydrochloric acid.
3.2 Preparation of reagents
3.2.1 Hydrochloric acid solution (10%, volume fraction): measure water and hydrochloric acid at the volume ratio of 9: 1 with measuring tube or pipette, place them in a proper container, and mix it uniformly.
3.2.2 Acetonitrile solution (40%, volume fraction): respectively measure acetonitrile and water at the volume ratio of 40: 60 with a measuring tube, place them in a proper container, and mix it uniformly.
3.2.3 Alkali extract: respectively measure acetonitrile, water and triethylamine at the volume ratio of 40:40:1 with measuring tube or pipette, place them in a proper container, and mix it uniformly.
3.3 Standard product
Standard product flourescent brightener 220 (C40H40N12O16S4Na4, abbreviation: C.I.220, CAS No.: 16470-24-9), with purity > 95%.
3.4 Preparation of standard solutions
3.4.1 Standard stock solution (1.00 mg/mL): in a dark condition, accurately weigh about 10mg (accurate to 0.1 mg) standard product C.I.220 to a beaker, dissolve it with alkali extract (3.2.3), transfer it to a 10mL brown volumetric flask, set the constant volume; preserve it at - 18℃ in a dark place, which will be valid for 90d.
3.4.2 Standard working solution (40.0 μg/mL): progressively dilute standard stock solution with acetonitrile solution (volume fraction 40%) to 40.0μg/mL standard working solution, preserve it at 4℃ in a dark place, which will be valid for 15d.
3.5 Materials
3.5.1 Gauze: with dimension of about 5cm × 5cm.
3.5.1 Glass cotton.
4 Instruments and Apparatus
Note: all instrument and apparatus directly contacting the specimen shall show no fluorescence under ultraviolet lamp.
4.1 Ultraviolet lamp: with wavelength of 365nm.
4.2 Scissors.
4.3 Deltoid plate.
4.4 Ultrasonic cleaner.
4.5 High speed crusher, with rotation speed ≥10000 r/min.
4.6 Rotary evaporator.
4.7 Constant temperature water bath.
4.8 PH meter: with accuracy of 0.1.
4.9 Analytic balance: with sensibility of 1 mg and 0.1 mg.
4.10 Obconical bottle: 250 mL.
4.11 Conical beaker with stopper: 250 mL.
4.12 Glass funnel.
4.13 Glass watch glass.
4.14 Tray.
4.15 Centrifuge: with rotation speed of ≥3500 r/min.
5 Analysis Steps
5.1 Preparation of specimens
Randomly take 5 pieces from specimens of paper or paper boards for food, like food wrap paper, candy paper and frozen sucker paper, cut them with a pair of scissors and a deltoid plate into 100 cm2 pieces.
Randomly take 2 pieces from the same batch of paper products for food, like paper glass, bowl, paper, box, dish and bag, and cut them with a pair of scissors and a deltoid plate to 100 cm2 pieces
For the specimen requiring confirmatory test, weigh 10 g (accurate to 1 mg), cut it into 5mm×5mm paper fragments, crush them with high speed crusher (with rotation speed of 10000 r/min) till flocculence, preserve it for standby. If it fails to be detected in a short time, put them in a clean PE bag, and keep it from light at the ambient temperature.
5.2 Direct determination of flourescent brightener
In a dark room or box, switch on the ultraviolet lamp and choose the wavelength of 365 nm. Place the prepared 100cm2 specimen at about 20 cm under the light source of the ultraviolet lamp, and observe whether the specimen has obvious blue or violet fluorescence. If the specimen shows multiple discontinuous fleck fluorescence or shows fluorescence but obscure, perform operation as specified in 5.3, and carry out the confirmatory test.
5.3 Confirmation of flourescent brightener
5.3.1 Preparation of standard reference gauze
Weigh 2.0 g (accurate to 1 mg) blank paper specimen (crushed uniformly as specified in 5.1) to a 250 mL conical beaker, add 0.5 mL C.I.220 standard solution (40.0 μg/mL) (equivalent to that the content of C.I.220 in paper specimen is 10 mg/kg); add 100 mL alkali extract (volume ratio of acetonitrile, water and triethylamine: 40:60:1) under dark condition (the required illumination is lower than 20 Lux), and perform ultrasonic extraction at 50℃ for 40 min. After extraction, cool it to the ambient temperature, filter the extract with a glass funnel containing a little glass cotton (free of fluorescent substance) to an obconical bottle, or centrifuge (at a rotation speed of 3500 r/min; for 5 min) it to obtain the clear extract. Depressurize the extract at 50℃ and concentrate it to about 40 mL ~ 50 mL, transfer the concentrated solution to a 250 mL beaker; wash the obconical bottle with water, add the washing liquor to the 250 mL beaker; adjust pH value with hydrochloric acid solution (10%, volume fraction) to 3 ~ 5, and scale the volume with water to about 100 mL. Immerse a 5 cm × 5 cm gauze in the extract, and adsorb at a 40℃ water bath for 30 min. Take the gauze out with a nipper, squeeze out a majority of liquid with hand, fold the gauze into four layers (each layer with an area of about 2.5 cm × 2.5 cm), and place it in a glass watch glass.
5.3.2 Extraction and adsorption of specimen
Weigh 2.0 g (accurate to 1.0 mg) blank paper specimen (crushed uniformly as specified in 5.1) and put into a 250 mL conical beaker, carry out operations below as specified in 5.3.1 herein "add 100 mL alkali extract (volume ratio of acetonitrile, water and triethylamine: 40:60:1) under dark condition....". Carry out two parallel tests on each specimen.
Foreword i
1 Scope
2 Principle
3 Reagents and Materials
4 Instruments and Apparatus
5 Analysis Steps
6 Judgment of Results
