Pesticide residue issues have attracted much attention since the “toxic vegetable event”in 1980s. The first generation of pesticide residue detecting card was produced in 1993, and was applied in vegetable export market of Shenzhen, then pesticide residue detecting card was widely used in institute of inspection and supervision, farmers’ market, supermarket, and canteen. Currently, this method has become national standard method and achieved good social benefits.

As China’sentry to the WTO and the continuous improvement of people’s living standard, it has become more and more urgent to develop more advanced and sensitive detecting products.

Presently, based on the development requirement of the market, our company has successfully developed high sensitive pesticide residue detecting card after two years hard research. Compared with previous pesticide residue detecting card, this new developed card has high sensitivity to organophosphorus and carbamate especially to chlorpyrifos. It is very suitable for exporting market, exporting & importing company and inspection & quarantine bureau. Now high sensitive pesticide residue detecting card has been exported to Korea. Welcome to contact us about our products.

The lowest detection limits of high sensitive pesticide residue detecting card to several commonly used pesticides are as follows (Unit: mg/kg):

Chlorpyrifos

0.6

Methamidophos

0.2

Parathion

0.1

Methyl parathion

0.04

Malathion

0.6

Carbofuran

0.5

Methomyl

0.1

Dimethoate

0.5

Omethoate

0.5

Dichlorvos

0.01

Trichlorphon

0.04

Phoxim

0.6

Carbosulfan

0.5

1. Using method:

1.1 Integrated detecting method

1.1.1 Select representative sample of vegetable, wipe the dirt on the surface of the sample and then cut the sample into small pieces (about 1cm²), take 5g sample into a bottle with cover, add 10mL pure water or buffer solution, then shake up about 50 times and stand for at least 2 minutes.

1.1.2 Remove the film of pesticide residue detecting card, dip the white pill into the treated solution (prepared in the step 1.1.1). Stand the card for at least 10 minutes for pre-reaction (place the card into thermostat device at 37℃ if it is possible).Make sure that the surface of the white pill is moist after pre-reaction.

1.1.3 Fold the card in half, pinch the card for 3 minutes (place it into thermostat device for 3 minutes if it is possible) to let the white pill and the red pill superimpose for reaction. Judge the results according to the color variation of the white pill.

1.1.4 There should be a blank control test with pure water or buffer solution each time.

1.2 Surfacedetecting method

1.2.1 Wipe the dirt on the surface of the vegetable. Add 2~3 drops of eluant on the surface of the sample, and then use another piece of vegetable to rub gently the part of the sample which is added the eluant.

1.2.2 Remove the film of pesticide residue detecting card, and drop the eluant of the samples onto the white pill.

1.2.3 Stand the card for at least 10 minutes for pre-reaction (place the card into thermostat device at 37℃ for 10 minutes if it is possible). Make sure that the surface of the white pillis moist after pre-reaction.

1.2.4 Fold the card in half, then pinch the card for 3 minutes (place it into thermostat device for 3 minutes if possible) to let the white pill and the red pill superimpose for reaction. Judge the results according to the color variation of the white pill.

1.2.5 There should be a blank control test with pure water or buffer solution each time.

2. Results determination

Compared with blank control test, it is positive result that the white pill does not change the color or it turns light blue. It indicates there is a high pesticide residue that the white pill does not change the color. And it indicates there is a relatively low pesticide residue that the white pill turns light blue. While it is negative result that the white pill turns azure or has the same color with blank control test card. For those samples of which the results are positive, use other analysis methods to determine the types and concentration of the pesticide.

3. Supplemental explanation

There are a lot of secondary metabolites in plants such as scallion, garlic, radish, Chinese chive, celery, coriander, zizania latifolia, mushroom and tomato which could result in false positive. Also, high chlorophyll vegetables could lead to pigment interference. It is recommended to soak entire vegetable leaves or adopt surface detecting method when dealing with these vegetables.

Reaction rate slows down when the temperature is below 37℃,so the reaction time should be extended accordingly when adding treated solution on the white pill. It is comparable only when samples detecting card and blank control detecting card have the same reaction time. There are two reasons for color invariable of the blank control test card. First, too little buffer solution was added onto the surface of the white pill or pill wasn't moist enough after pre-reaction; second, the temperature was too low.

Pesticide detecting card is so sensitive to the pesticide that the card wouldn't turn blue if there is small amount of pesticide attached to operators or apparatus.

3 minutes would be the right time for the reaction when white pill superimpose red pill. The blue color would become increasingly deeper after 3 minutes, and the color fades away after 24 hours.

4. Retention period:

It should be placed in the shade and dry environment without light. If possible, it is better to placed in the refrigerator at 4℃ temperature. Pesticide residue detecting card which is open should be exhausted within 3 days, if it can’t be exhausted at a time, place it in the dry container and exhaust it within one week. The expiration time is one year.