Rapid detection of melamine in dairy products (colloidal gold immunochromatographic competition method)

[Detection significance]

Melamine (Melamine, CAS: 108-78-1) molecular formula is C ₃ N ₆ H ₆ or C ₃ N ₃ (NH ₂ ) ₃ , the scientific name is 1,3,5-triazine-2,4,6-triazine Amine, abbreviated as triamine and melamine, is a diazine type nitrogen-containing heterocyclic organic compound

Currently, food melamine detection methods are mainly IPLC, HPLC-MS, GC- MS, ELISA method, a capillary electrophoresis method and the like

This method is applicable to melamine in raw milk, pure milk, pure milk powder, pure yogurt, and feed (plant by-product feed such as soybean protein, rice protein concentrate, crushed corn and dried husk fiber, wheat bran, potato protein, etc.

[Detection principle]

The test solution was added Calgary speed measurement sample hole, the detection of liquid melamine with gold-labeled antibody gold conjugate pad to form a complex, if the melamine concentration is less than 1000ng / mL solution in detection, the gold-labeled antibody unbound to flow In the T zone, it is bound by the melamine-bovine serum albumin (BSA) conjugate fixed on the membrane, and gradually condenses into a visible T line

If the melamine concentration is higher than 1000ng/mL, all gold-labeled antibodies will form a complex and will no longer combine with the melamine-BSA conjugate at the T line to form a visible T line

The unfixed composite flows through the T zone and is captured by the secondary antibody in the C zone and forms a visible C line

[Steps]

(1) Raw material processing

① Raw milk: Take 1mL of raw milk for production and add it to a 1.

②Milk powder or feed: Take 1g sample in a test tube towel, add 5mL pure water, put the test tube into a cup of boiling water, shake to dissolve the sample, centrifuge to separate it, the dilute solution is the test solution

③Fresh milk: use the sample directly for testing

(2) Determination Put the melamine test card on a clean and flat table, and use a plastic pipette to drop 3 drops of the air-free sample treatment solution vertically into the sample hole (S); wait for the appearance of the purple band, the test result should be in Read at 5min

[Result Judgment]

As shown in Figure 7-1

Figure 7-1 Schematic diagram of the judgment of fast detection of melamine by colloidal gold immunochromatographic competition method

(1) Sensitivity (threshold) is determined by the control concentration of each detection card.

(2) Positive (+) Only a purple-red band appears in the quality control area (C), and no purple-red band appears in the test area (T)

(3) Negative (-) Two purple-red stripes appear

(4) There is no purple-red band in the invalid quality control area (C), which indicates an incorrect operation process or the test card has deteriorated and damaged.

(5) A positive result indicates that the melamine content is above the threshold , and a negative result indicates that the melamine content is below the threshold

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