Pesticide residues rapid test reagent which has the characteristic of well stability and high sensitivity are the matching reagents corresponding to industrial standard NY/T 448-2001, and could be used on various types of pesticide detecting instrument.
1. Principle
Pesticide of organophosphorus and carbamate could inhibit the activity of cholinesterase under certain conditions. Whether the samples contain organophosphorus or carbamate could be determined through the calculation of inhibition rate, which has positive correlation with pesticide concentration.
2. Reagents preparation
2.1 Buffer solution: Dissolve one pack of buffer powder with 1000mL pure water or distilled water, store at room temperature.
2.2 Cholinesterase: Use directly, store at 4℃.
2.3 Chromogenic agent: Dissolve one bottle of chromogenic powder with 25mL buffer solution , store at 4℃.
2.4 Substrate: Dissolve one bottle of substrate with 10mL pure water or distilled water, store at 4℃.
Special tips: Pesticide residue rapid test reagent can be used in various types of pesticide detecting instrument and spectrophotometer.
3. Sample preparation
3.1 Weigh 2g vegetable samples (weigh 4g if it is tuber), cut the samples into 1cm2.
3.2 Soak the samples with 20mL buffer solution, shake it for 1~2min.
3.3 Pour out the above treated solution and stand it for 2 minutes. If the treated solution is muddy or has so many impurities, filter it first before doing the test.
4. Starting instrument
Connect the instrument with power, press the “enter” button allowing the instrument to self-checking which will take about 1min, instrument is ready to use after self-checking process.
5. Detection
5.1 Blank Control detection:
5.1.1 Suck 3mL buffer solution into beaker; add 50μL chromogenic reagent and cholinesterase respectively; Mix them evenly and stand it for 30mins at 37℃.
5.1.2 Add 50μL substrate into the beaker, shake them fully and then pour the solution into cuvette, put it in the test channel of the instrument, close the lid and press the “contrast” button. It tests the variation of absorption value (412nm) (△A0) in 3 minutes.
5.2 Sample detection
5.2.1 Suck 3mL samples solution to text tube; add 50μL chromogenic reagent and cholinesterase respectively; shake them evenly and stand it for 30mins.
5.2.2 Add 50μL substrate into the test tube, shake it fully and then pour it into cuvette, put it in the test channel of the instrument, close the lid and press the “Sample” button. It tests the variation of absorption value (412nm) (△At) in 3 miutes.
6. Results:
Inhibition rate could be calculated by formula: [( ΔΑ 0 －ΔΑ t )/ ΔΑ 0 ]×100% ;
Normally, Inhibition rate could be calculated by pesticide detecting instrument automatically.
Inhibition rate≥70%: Positive result, it is recommended to detect again with gas chromatography.
Inhibition rate≤70%: Negative result.
Tips :
During the step of adding substrate, put the substrate in the cuvette in advance. Once the standing time is off, immediately pour the solution into the cuvette in which there is substrate already, and then place the cuvette quickly in the test channel. This way can avoid the error caused the long time of adding substrate when detecting multiple samples.
7. Retention Period
It should be stored at 4℃, and the expiration time is 12 months.
8. Matters need attention
8.1 Pesticide residue test reagent include 20 packages of buffer powder, 5 bottles of cholinesterase, 2 bottles of chromogenic reagent, and 5 bottles of substrates.
8.2 When using any reagent, please exhaust the open one before reopening a new one in case they go bad.
8.3 Biochemical reaction will occur immediately when enzyme, substrate and chromogenic reagent meet together. So pipette and container should be labeled , used alone in order to avoid cross-contamination.
8.4 When sucking the reagent from the bottle, it is strictly forbidden to inject the reagent back to the bottle.
8.5 Insulation measures should be used if the environment temperature is too low ( less than 20℃).
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