The State Food and Drug Administration publicly solicited opinions on the rapid detection method of food on "Colloidal Gold Immunochromatographic Method for Rapid Detection of Sudan Red I in Chili Products (Draft for Comment)"

Recently, in accordance with the relevant provisions of the "Food Safety Law of the People's Republic of China", in order to standardize the use of rapid food detection methods, the China Food and Drug Administration organized the development of the "Colloidal Gold Immunochromatographic Method for Rapid Detection of Sudan Red I in Chili Products (Request for Draft)" food rapid detection method, has been open to the public for comments.

1 Scope

This method specifies the rapid detection method of colloidal gold immunochromatography for Sudan red I in pepper products.

This method is suitable for the rapid determination of Sudan Red I in chili sauce, chili oil and chili powder.

2 Principles

This method adopts the principle of competitive inhibition immunochromatography. Sudan red I in the sample binds to the specific antibody labeled with colloidal gold, which inhibits the binding of the antibody to the antigen on the detection line (T line), resulting in a change in the color of the detection line, passing the detection line and the control line (C line) The color depth was compared, and the Sudan Red I in the sample was qualitatively determined.

3 Reagents and Materials

Unless otherwise specified, the reagents used in this method are all analytically pure, and the water is secondary water specified in GB/T 6682.

3.1 Reagents

3.1.1 Acetonitrile.

3.1.2 Anhydrous magnesium sulfate.

3.1.3 n-hexane.

3.1.4 Dichloromethane.

3.1.5 Sodium hydroxide.

3.1.6 Sodium hydroxide solution (2mol/L): Weigh 8g of sodium hydroxide (3.1.5), dissolve in water and dilute to 100mL.

3.1.7 Absolute ethanol.

3.1.8 Reconstitution solution: Mix anhydrous ethanol (3.1.7) and water in a volume ratio of 25:75.

3.2 Reference materials

The Chinese name, English name, CAS accession number, molecular formula, and relative molecular weight of the Sudan Red I reference substance are shown in Table 1, and the purity is >95%.

Table 1 Chinese name, English name, CAS accession number, molecular formula and relative molecular weight of Sudan Red I reference substances

Chinese name	English name	CAS login number	Molecular formula	Relative molecular weight
Sudan Red I	Sudan I	842-07-9	C16H12N2O	248.28

Note: or equivalent traceable substances.

3.3 Preparation of standard solution

3.3.1 Sudan Red I standard stock solution (1mg/mL): Accurately weigh an appropriate amount of Sudan Red I reference material (3.2), put it in a 10mL volumetric flask, add an appropriate amount of acetonitrile (3.1.1) and dissolve it by ultrasonic. Dilute to the mark with acetonitrile, shake well, and prepare a standard stock solution of Sudan I with a concentration of 1 mg/mL. Store at -20 ℃ away from light, valid for 6 months.

3.3.2 Sudan Red I Standard Intermediate Solution (1μg/mL): Precisely measure 100μL of Sudan Red I Standard Stock Solution (1mg/mL) (3.3.1), put it in a 100mL volumetric flask, Dilute to the mark with acetonitrile (3.1.1), shake well, and prepare a standard intermediate solution of Sudan Red I with a concentration of 1 g/mL.

3.4 Materials

3.4.1 Solid phase extraction cartridge: CNW Poly-sery MIP-SDR solid phase extraction cartridge (200mg/3mL), or equivalent.

3.4.2 Sudan Red I Colloidal Gold Immunochromatography Kit, the applicable matrix is ​​chili sauce, chili oil and chili powder.

3.4.2.1 Gold-labeled microvias.

3.4.2.2 Test strips or test cards.

4 Instruments and Equipment

4.1 Pipettes: 200μL, 1mL and 5mL.

4.2 Vortex mixer.

4.3 Centrifuge: speed >4000r/min.

4.4 Electronic balance: the sensing capacity is 0.01g.

4.5 Nitrogen blower.

4.6 Water bath.

4.7 Environmental conditions: temperature 15℃～35℃, humidity <80%.

5 Analysis Steps

5.1 Sample Preparation

Take an appropriate amount of sample, mix liquid samples or semi-solid samples thoroughly, and fully smash and mix solid samples.

5.2 Extraction of samples

5.2.1 Chili Sauce

Weigh 2g of chili sauce (accurate to 0.01g) into a 15mL centrifuge tube, add 0.5g of anhydrous magnesium sulfate (3.1.2) and 5mL of n-hexane (3.1.3) extract, and vortex for 1min. Centrifuge at 4000r/min for 5min. All the supernatant was added to the solid phase extraction column (3.4.1), and the effluent was discarded. Then 6 mL of n-hexane was added to rinse the solid phase extraction column, and the effluent was discarded. Elute the solid phase extraction cartridge with 2 mL of dichloromethane (3.1.4), collect the eluate and dry it. Precisely add 400 µL of the reconstituted solution (3.1.8), vortex and mix for 1 min, as the solution to be tested, and measure immediately.

5.2.2 Chili Oil

Weigh 5g of chili oil (accurate to 0.01g) into a 15mL centrifuge tube, add 8mL of n-hexane (3.1.3) for extraction, vortex for 1min, and add all the supernatant to the solid phase extraction column , the effluent was discarded. Then 6 mL of n-hexane was added to rinse the solid phase extraction column, and the effluent was discarded. Elute the solid phase extraction cartridge with 2 mL of dichloromethane (3.1.4), collect the eluate and dry it. Precisely add 400 µL of the reconstituted solution (3.1.8), vortex and mix for 1 min, as the solution to be tested, and measure immediately.