Quality control measures in pesticide residue testing process

Quality control: operation techniques and activities that meet quality requirements

Do the preparatory work before the sample testing, including preparation equipment, reagents, drugs, the environment, containers and the like

Inspection of equipment and equipment: Before the start of each inspection work, necessary inspection and maintenance of the equipment should be carried out, and the working conditions of the equipment should be adjusted to make the equipment in the best working condition

Inspection of reagents and medicines: Each batch of reagents and medicines should be inspected for conformity according to the detection method, and the impurities should be checked to eliminate the interference of the reagents on the test results.

Environmental inspection: During the inspection work, the environment of the laboratory, sample storage room, pre-processing room and instrument room should be controlled to ensure that the temperature and humidity of the environment meet the requirements of the inspection

Inspection of inspection utensils: Volumetric flasks, pipettes and other utensils used for pesticide residue inspection must be effectively cleaned before use to prevent cross-contamination

When measuring samples, make reagent blanks and sample blanks (non-interference samples are used for matrix matching standard solutions) to determine whether there is interference

The quality control methods that can be used usually include the following:

1.

2.

User comparison: Under the same environment, equipment, and method conditions, different people measure the same parameter

Instrument comparison: Under the same environment, personnel, and method conditions, use different instruments to measure the same parameter

3.

4.

5.

6.

Sample addition and recovery: Take two copies of the same sample, and one of them is added with the quantitative standard substance of the component to be tested

For its calculation method, a theoretical formula is given:

Standard recovery rate = (measured value of spiked sample-measured value of sample) ÷ spiked amount × 100%

It should be noted that: ①The sampling volume of the sub-sample of the same sample must be equal; ②The measurement process of various sub-samples must be carried out in the same operation steps; ③The amount of standard addition should be as close as possible to the content of the analyte in the sample, and attention should be paid to The influence of sample volume; the standard addition amount should not be too large, generally 0.
5 to 2.
0 times the content of the analyte, and the total content after addition should not exceed the upper limit of the method; ④The concentration of the standard addition solution should be higher, and the standard addition The volume of the object should be small, generally not more than 1% of the original sample volume
.

Pesticide testing additives generally take the maximum residue limit of the sample and the method quantification limit as the required concentration, that is, at least 2 additive concentrations must be selected for the recovery test
.
When there is no reference to the maximum residue limit value, the method quantification limit and the concentration 10 times higher than the method quantification limit are used as the addition recovery rate, and each concentration is subjected to more than 5 repeated tests
.
The result of adding recovery rate should be close to 100%, but due to the influence of many factors such as impurity interference and operation error, the actual result will be very different
.
Refer to Table 2-11 for the reference range of recovery rate
.

Table 2-11 Requirements for recovery rate of different addition levels

Related links: GB23200.
8-2016 Chinese gas chromatography-mass spectrometry