Development and validation of a modified QuEChERS-LC-MS/MS method for seven herbicides in cereals

Cereals are major staple foods, and seven newly registered herbicides have been permitted for cereal production in China. GB 2763-2026 set temporary maximum residue limits for these compounds, yet no official multi-residue detection method is available. This study aimed to develop and validate a modified acidified Quick, Easy, Cheap, Effective, Rugged and Safe liquid chromatography-tandem mass spectrometry (QuEChERS-LC-MS/MS) method for simultaneous determination of pinoxaden, monosulfuron-ester, pyribambenz-propyl, quintrione, pyraclonil, tripyrasulfone and tefuryltrione in wheat flour, brown rice and corn.

Adding 10 mL L^-1 formic acid into acetonitrile markedly improved the low recoveries of quintrione and tefuryltrione, raising recoveries from 52.1-62.3% to 88.6-91.5%. After optimizing hydration volume, vortex extraction time and primary secondary amine + C18 mixed sorbents, matrix effects were controlled within 0.81-1.19. Good linearities were obtained (r² > 0.9945) over 5-100 μg L^-1. Limits of detection ranged from 0.01 to 1.08 μg kg^-1. Limits of quantification were 10 μg kg^-1, defined as the lowest validated spiked level meeting SANTE/11312/2021 criteria. At three spiked levels (10, 20 and 100 μg kg^-1), mean recoveries were 78.5-118.5% with relative SD values of 1.9-8.8%, complying with SANTE/11312/2021 criteria. Among 80 real cereal samples, only three samples contained trace herbicide residues far below national temporary maximum residue limits.

The validated acidified QuEChERS-LC-MS/MS method is sensitive, rapid and reliable for monitoring seven herbicides in cereals. The formic acid-assisted extraction strategy provides a universal reference for multi-residue analysis of polar, easily-adsorbed pesticides in cereal matrices. © 2026 Society of Chemical Industry.