Persistence, decontamination and dietary risk assessment of propyrisulfuron residue in natural paddy field environment using QuEChERS@UPLC-Q-TOF-MS/MS

A modified QuEChERS technology combined with UPLC-Q-TOF-MS/MS residue analytical method for propyrisulfuron in natural paddy field environment was developed. Propyrisulfuron residues in paddy water, soil, rice plants, brown rice and rice husk samples was extracted with 1.0 % acetic acid-acetonitrile (v/v) solution and separated on a reversed-phase C18 column with a mobile phase of 0.1 % formic acid water-acetonitrile eluted by isometric elution (60/40, v/v), and quantified in high-resolution multiple reaction monitoring (MRMHR) scanning mode providing more accurate confirmatory information. The lower limit of quantification (LOQ) of propyrisulfuron in all the five paddy matrices was in a range of 1.24 ∼ 3.85 µg/kg, and all calibration curves showed good linearity (R2 > 0.991) in a certain concentration range (10 ∼ 1000 µg/kg). At the spiked level of 10 ∼ 200 µg/kg, the intra-day and inter-day average recoveries and relative standard deviation were 82.80 ∼ 106.93 % and 1.81 ∼ 5.51 %, 83.05 ∼ 105.84 % and 2.25 ∼ 4.61 %, respectively, for analysis on three consecutive days, and there was a good retention time repeatability of 15 consecutive injections with RSD of 0.15 ∼ 0.17 %, indicating a high sensitivity, specificity, accuracy and precision. All paddy filed environmental samples frozen at −20 °C were analyzed within 10 weeks after collection for a good storage stability. Propyrisulfuron dissipated in paddy water, soil and rice plants at application doses of 30, 45 and 60 g a.i./ha with half-lives of 1.37 ∼ 1.81, 4.10 ∼ 5.35 and 3.70 ∼ 4.42 days in 2020, 1.44 ∼ 2.04, 4.27 ∼ 5.83 and 3.68 ∼ 4.49 days in 2021, respectively. The final propyrisulfuron residual levels of two years in brown rice, rice husks and rice plants samples prior to harvest were lower than 8.18 µg/kg, and its removal rate was in a range of 1.40 to 98.27 % by several simple available household technologies. Moreover, the chronic dietary risk in brown rice at recommended dose for Chinese residents of different age groups was low and acceptable for daily consumption.