A multiresidue analytical method using a modification of the “quick, easy, cheap, effective, rugged, and safe” (QuEChERS) sample preparation approach combined with liquid chromatography–tandem mass spectrometry (LC-MS/MS) analysis was established and validated for the rapid determination of 69 pesticides at different levels (1–100 ng/g) in wheat and rice straws. In the quantitative analysis, the recoveries ranged from 70 to 120%, and consistent RSDs ≤ 20% were achieved for most of the target analytes (53 pesticides in wheat straw and 58 in rice straw). Almost all of the analytes achieved good linearity with R2 > 0.98, and the limit of validation levels (LVLs) for diverse pesticides ranged from 1 to 10 ng/g. Different extraction and cleanup conditions were evaluated in both types of straw, leading to different options. The use of 0.1% formic acid or not in extraction with acetonitrile yielded similar final outcomes, but led to the use of a different sorbent in dispersive solid-phase extraction. Both options are efficient and useful for the multiresidue analysis of targeted pesticides in wheat and rice straw samples.Keywords: animal feed; LC-MS/MS; multiresidue pesticide analysis; QuEChERS; rice and wheat straw;

In this study, a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was established for the extraction and cleanup of fipronil and its three metabolites (fipronil solfone, sulfide, and desulfinyl) in peanut kernel, shell, straw, seedling, and soil samples, and liquid chromatography–tandem mass spectrometry (LC-MS/MS) was used for analysis. The average recoveries were 66–116% at the level of 0.001–0.1 mg/kg with the RSD <19%, and the limit of detection was 0.3 ng/g for all matrices. The dissipation experiment results demonstrated that fipronil dissipated more rapidly in peanut seedling than in soil, with half-lives of <1 day in peanut seedling and 32–57 days in soil depending on the soil pH. The final residues at harvest of peanut kernels were all below 0.02 mg/kg, whereas in peanut shell and straw, the total highest residues were 0.99 and 0.30 mg/kg, respectively. Fipronil-desulfinyl and fipronil-sulfone were the highest residue metabolites in peanut plant (seedling and straw) and soil samples, respectively.

The dissipation and final residues of picoxystrobin in peanut and soil were determined by a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method and high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The dissipation and final residue of picoxystrobin at three different provinces (Hebei, Hubei, and Shandong) in China were studied. The fortification experiments at three different spiking levels of 0.01, 0.05, and 0.5 mg kg−1 in all matrices (soil, peanut seedling, shell, stalk, and kernels) were conducted, and the recoveries were 79–114 % with relative standard deviations of 3–12 % (n = 5). The dissipation half-lives of picoxystrobin were 1.5–8.6 days in soil, and 2.1–2.8 days in seedlings. The final residues of picoxystrobin in supervised field trials were 0.05–6.82 mg kg−1 in stalk, ≤0.381 mg kg−1 in soil, ≤0.069 mg kg−1 in shells, and ≤0.005 mg kg−1 in peanut kernels. Considering the final residue levels and the maximum residue limits (MRLs), the pre-harvest interval of 14 days was recommended for the safe use of picoxystrobin in peanut crop.

The objective of this experiment was not only to provide a simple residue analytical method to evaluate the safe application rate of Emamectin Benzoate for paddy crops but also to give a suitable recommended dosage in paddy crops. Paddy samples were detected using HPLC–MS/MS. The half-lives of emamectin benzoate in paddy plants, water and soil were 2.04–8.66 days, 2.89–4.95 days and 3.65–5.78 days with a dissipation rate of 90% over 7 days after application, respectively. Low residues and short half-life suggested that Emamectin Benzoate could be safely used in paddy crops with the suitable dosage and application.

A simple, quick and reliable residue analytical method for flusilazole in apple and soil was developed in this study. The samples were extracted with acetonitrile and determined by liquid chromatography with UV detection. The LOQ of the method was 0.02 mg/kg. The dissipation dynamic and final residues of flusilazole in apple and soil were studied using field trial method. The results of residual dynamics experiment showed that after the apple was treated by flusilazole at treble of recommended high dosage (3.75 g/kg H2O), the half-life times of flusilazole in apple and soil were 4.23–7.77 days and 3.04–5.14 days, respectively. Residues of flusilazole in apple at harvest time were all below 0.05 mg/kg at both recommended high dosage and 1.5 times of recommended high dosage.

A simple, sensitive method for the analysis of nicosulfuron in corn and soil was developed. Samples were extracted with acetonitrile: water (2:3, V/V) mixture and partitioned with dichloromethane. After concentration, the soil sample extracts were detected using high performance liquid chromatography–ultraviolet detector (HPLC–UVD), and the corn sample extracts were detected using high performance liquid chromatography-mass spectrometry detector (HPLC–MSD). The fortified recoveries at 0.05–1.0 mg/kg were 79.7%–115.8%, with the relative standard deviation of 1.40%–13.8%. The limit of detection of the analytical method was 0.05 ng at a signal-to-noise ratio of 3, and the limit of quantification was 0.05 mg/kg for both corn and soil. The dissipation dynamics of nicosulfuron in the field trials in Beijing and Changchun were investigated. The half-lives of nicosulfuron in corn plants were 0.73 days in Beijing and 0.53 days in Changchun, both with a dissipation rate of 90% over 7 days after application. The half-lives in soil were 13.64 days both in Beijing and in Changchun with a dissipation rate of 90% over 21 days. Low residues and short half-life in corn suggested that nicosulfuron could be safely used in corn crops with the suitable dosage and application.

A specific, sensitive method was developed for the analysis of chlormequat in wheat and soil by high performance chromatography/mass spectrometry. The fortified recoveries of soil were from 75.08% to 96.55%, with RSD 3.34%–15.18%, the limit of detection of the analytical method was 0.05 ng at a signal-to-noise ratio of 3, and the limit of quantification was 0.05, 0.1, 0.5 mg/kg for soil, wheat plants and wheat grain, respectively. The degradation dynamics and final residues of chlormequat in Beijing and Changchun were investigated. The half-life of chlormequat in wheat plants were 3.15 days in Beijing and 4.56 days in Changchun, while the half-life in soil was 3.88 days in Beijing and 4.51 days in Changchun. The final residues of chlormequat in soil were not detectable, and the final residues of chlormequat in wheat grain were below 0.50 mg/kg except for 3.51 mg/kg from high dosage plot of Changchun. The fact that all the final residues were below 5 mg/kg (GB2763 in National standards of the People’s Republic of China, maximum residue limits for pesticide in food, Beijing, 2005) suggested that chlormequat could be safely used in wheat crops with the suitable dosage and application.

Solid-phase extraction and gas chromatography with electron-capture detection has been used for sensitive, simple, and reliable analysis of carfentrazone-ethyl residues in water. Carfentrazone-ethyl was enriched by use of multiwalled carbon nanotubes (MWCNT), a new adsorptive material. Several conditions affecting recovery of the analyte, for example polarity and volume of eluents, pH of water samples, and sample volume, were studied. Recovery from fortified samples, linear range, and limit of detection were evaluated. The results showed that MWCNT are an efficient SPE adsorbent for preconcentration of carfentrazone-ethyl in water. Under the optimized SPE conditions, recovery of carfentrazone-ethyl from fortified water was 81.49–91.08%, with RSD from 1.66 to 8.21%. The limits of detection and quantification were 0.01 and 0.03 µg L−1, which were lower than the MRL stipulated by the EU for individual pesticides in water (0.1 µg L−1). Finally, the method was applied to tap water and river water; the results showed that the method was suitable for detection of carfentrazone-ethyl in environmental water samples.

The analytical method of S-metolachlor residue and its degradation in cotton and soil in trial field were investigated. S-metolachlor EC (96% w/w) was applied as pre-emergence at dosages of 1,500 and 2,250 ml ha−1 3 days after sowing of the cottonseeds in the field. The soil and the plant samples were collected at different intervals and the residues of S-metolachlor were analyzed by GC–ECD. The results showed that the degradation of S-metolachlor in cotton leaves in Beijing and Nanjing coincides with C = 0.1113e−0.1050t and C = 0.1177e−0.1580t, respectively; the half-lives were about 6.6 and 4.4 days. The degradation of S-metolachlor in soil in Beijing and Nanjing coincides with C = 1.0621e−0.0475t, and C = 0.9212e−0.0548t, respectively; the half-lives were about 14.6 and 12.6 days,. At harvest time, the S-metolachlor in cotton seeds and soil samples were detected by GC–ECD and confirmed by GC/MS. The results showed that the residues in cottonseeds were lower than the USA EPA’s maximum residue limit of 0.1 mg kg−1 in cottonseed. It could be considered as safe to human beings and environment.

The purpose of this article was to establish a simple residue analysis method for S-metolachlor in maize and to study its dissipation and residue in maize field eco-system. The results showed that S-metolachlor declined rapidly in maize seedling and soil after application. The half-lives of S-metolachlor in maize seedlings in Beijing and Changchun were 6.68 and 4.85 days, respectively, and in soil were 12.81 and 14.81 days, respectively. The terminal residues of S-metolachlor in soil samples were very low (around 0.005–0.045 mg/kg), and the residues in maize seeds were not detectable. The use of S-metolachlor according to the recommended dosages in maize could be considered safe.