Determination of 26 herbicide residues in soil， sediment， and surface water samples using modified QuEChERS method combined with ultra-high performance liquid chromatography-tandem mass spectrometry

As chemical agents that selectively inhibit weed growth， herbicides play a crucial role in enhancing crop yields. With increasing weed resistance， the environmental residue problems caused by excessive application have become increasingly prominent. Studies indicate that only 20%-30% of field-applied herbicides are effectively utilized， with the remainder entering environmental media such as the atmosphere， soil， sediment， and surface water through runoff and leaching. Recent frequent occurrences of vegetable phytotoxicity incidents in Shanghai have been traced to potential associations with herbicide residues in surface water， further highlighting the urgent need to establish multi-residue analytical methods for environmental media. An analytical method was established based on ultra-high performance liquid chromatography-tandem mass spectrometry （UHPLC-MS/MS） for determining 26 herbicide residues in soil， sediment， and surface water. Instrumental detection parameters were optimized， including electrospray ionization mode， mobile phase， and chromatographic column. The mobile phase consisted of 0.1% formic acid aqueous solution （A） and acetonitrile （B） with the following gradient elution program： 0-0.5 min， 2%B； 0.5-1 min， 2%B-50%B； 1-4 min， 50%B-65%B； 4-6 min， 65%B-75%B； 6-8 min，75%B-85%B； 8-10 min， 85%B-95% B； 10-11 min， 95%B. Soil and sediment samples were extracted via acetonitrile oscillation followed by salting-out and purified using the QuEChERS method. Surface water samples were directly analyzed after acetonitrile extraction without purification. Different amounts of purification agents were investigated during sample pretreatment. Calibration curves were established by plotting the relationship between analyte concentration and measured peak area using pure solvent and matrix-matched standards. All 26 herbicides showed good linearity in the range of 0.1-50 μg/L with correlation coefficients exceeding 0.999 0. Matrix effects ranged from -35.2% to 14.6% across different matrices. Limits of quantification （LOQs） were 0.5 μg/kg for soil and sediment， 0.1 μg/L for water samples. The herbicides were spiked into soil and sediment at spiked levels of 0.5， 1， and 10 μg/kg， and into surface water at 0.1， 1， and 10 μg/L， respectively. The average recoveries for the 26 herbicides in soil， sediment， and surface water were in the ranges of 73%-108%， 73%-102%， and 74%-110%， respectively. The RSDs for the 26 herbicides were in the ranges of 4.5%-16.2%， 3.8%-19.7%， and 4.0%-15.0%， respectively. The developed method was applied to analyze the contamination status of the 26 herbicides in environmental samples collected from six vegetable cultivation zones in Shanghai. Results revealed distinct pollution patterns： In soil matrices， prometryn （PMT）， metolachlor （MTA）， and sulfometuron-methyl （SMTM） showed higher detection rates of 52.9%， 52.9%， and 29.4%， respectively， with content ranges of 0.8-490.4 μg/kg， 0.5-219.8 μg/kg， and 1.0-562.6 μg/kg. Sediment samples exhibited an 83.3% detection rate for PMT （1.5-6.7 μg/kg）. In surface water， SMTM， PMT， and simetryne （STN） were detected with maximum contents of 12， 2.5 and 1.1 μg/L， respectively， indicating differential migration behaviors across environmental compartments. The proposed method is simple， rapid， accurate， stable， and highly practical. It can be used to detect the 26 herbicide residues in soil， sediment， and surface water and provides a reference for monitoring the residual pollution and environmental behavior of herbicides.