Pesticide residues refer to the highly toxic and difficult-to-degrade pesticides sprayed on vegetables, fruits, tea leaves, Chinese herbal medicines and other crops during their growth process in order to increase crop yields and prevent the occurrence of plant diseases and insect pests, resulting in pesticide residues in the soil and water, which reach the human body through the food chain and cause harm. Long-term intake of vegetables and fruits with pesticide residues can induce chronic diseases, lead to human brain dysfunction, and cause some incurable diseases such as Parkinson's disease, Alzheimer's disease, cardiovascular and cerebrovascular diseases, diabetes, neurological diseases, etc.; it can also cause liver lesions, and even induce cancer in severe cases.

     The "Sanitary Standard for Drinking Water" is an important basis for China to carry out drinking water quality supervision and management. The current "Sanitary Standard for Drinking Water" (hereinafter referred to as the "original standard") has been implemented for nearly 15 years since July 1, 2007, and has played an important role in improving the quality of drinking water in China and ensuring the safety of drinking water quality. In recent years, China's rural living environment has improved significantly, and the people's demand for improving the quality of drinking water has become increasingly strong. The relevant departments revised the original standard in a timely manner and issued the "Sanitary Standard for Drinking Water" (hereinafter referred to as the "new standard") on March 5, 2022, which will be officially implemented on April 1, 2023. The new standard adds standard test methods for liquid chromatography tandem mass spectrometry for bentazon, 2,4-D (2,4-D), atrazine, methyl parathion, etc. Therefore, based on the new drinking water standard "GB/T 5750.9-2022 Standard Test Method for Drinking Water Part 9: Pesticide Index", this application center has established a method for determining the content of six pesticide residues in drinking water, including carbofuran, atrazine, methyl parathion, acetochlor, bentazone and 2,4-D, using ultra-high performance liquid chromatography-triple quadrupole tandem mass spectrometry . This method is fast, simple and highly sensitive, and provides a reference for the detection of carbofuran, atrazine, methyl parathion, acetochlor, bentazone and 2,4-D in drinking water.

Keywords: LC-MS/MS, environment, drinking water, pesticide residues, GB 5749-2022

Experimental part

instrument

Table 1 Liquid chromatography tandem triple quadrupole mass spectrometer

Table 2 Detection parameters of liquid chromatography tandem triple quadrupole mass spectrometer for positive ion detection compounds

Reagents and standards

Reagents: mass spectrometry grade formic acid, chromatography grade acetonitrile;

Pure water: 18.2 MΩ·cm deionized water (25°C);

Standards: Six pesticide residue standards, including carbofuran, atrazine, methyl parathion, acetochlor, bentazon and 2,4-D, were purchased from Tanmo Quality Inspection.

Sample preparation

The water samples were directly sampled and analyzed after being filtered through a 0.22 mm microporous filter membrane.

Linearity and detection limits

A series of 6 pesticide residues were diluted with methanol to obtain mixed standard solutions. The samples were injected according to the above method, and the standard curve was fitted by external standard method. The linear concentration range is shown in Table 1. The MRM superimposed chromatogram of the linear minimum point standard (0.1 ng/ml) is shown in Figure 2. The linear minimum point concentration standard solution was prepared for injection, and the quantification limit and detection limit were calculated according to S/N=10 and S/N=3. The results are shown in Table 2.

Table 1 Linear information of six pesticides

Figure 2 MRM overlay chromatograms of 6 pesticide residues at 0.1ng/ml standard

Table 2 Detection limits and quantification limits of six pesticide residues

Repeatability

A reference solution with a concentration of 10 ng/ml was prepared and injected 6 times continuously to examine the repeatability of retention time and peak area. The results are shown below.

10ng/ml repeatability: The RSD value of peak area is between 2.38% and 4.81%, and the RSD value of retention time is between 0.0% and 0.21%.

It can be seen that the peak area RSD and retention time RSD of all compounds are below 5% and 0.21%, and the precision is good.

Conclusion

This article examines the linearity, precision, sensitivity and other indicators for the determination of six pesticide residues: carbofuran, atrazine, methyl parathion, acetochlor, bentazone and 2,4-D in drinking water. The experimental results show that the six pesticide residues have good linearity within the detection range, and the correlation coefficients r are all greater than 0.998. The peak area and retention time RSD of six consecutive injections at a concentration of 10 ng/ml are below 4.81% and 0.21% respectively. Precision is good. The detection limit range of the six pesticide residues is approximately 0.0018~0.0407 ng/ml, and the quantification limit range is approximately 0.0054~0.71 ng/ml; the sensitivity meets the standard requirements. Using a highly sensitive and highly anti-pollution ultra-high performance liquid chromatography-triple quadrupole tandem mass spectrometer system, carbofuran, atrazine, methyl parathion, acetochlor, and bentazone in drinking water can be detected and 2,4-D for sensitive and accurate quantitative detection of six pesticide residues.

appendix

Equipment and consumables solutions

1. EXPEC 5210 Configuration Details

2. Standard products