Analysis of Pesticide residues in brown rice using modified QuEChERS multiresidue method combined with electrospray ionization-liquid chromatography-tandem mass spectrometric detection

A Review on Recent Innovations of Pretreatment and Analysis Methods for Sulfonylurea Herbicides

Sulfonylurea herbicides (SUHs) are widely used in agriculture because of their low dosage, low cost, and high selectivity. However, due to improper use and lack of effective management, their residues pose a threat to the human health through environment and food pollution. Therefore, there is a need for simple, quick, economical, and effective methods to analyze SUHs in plant-derived foods, crops, and environmental samples. The present article presents a comprehensive review of the pretreatment and analytical technologies used for SUHs in various sample matrices, focusing on the developments since 2010. The main pretreatment methods include liquid-liquid extraction, solid-phase extraction, QuEChERS, and different microextraction methods, whereas analytical methods mainly include liquid chromatography coupled with different detectors, capillary electrophoresis, among others. In addition, the present study also compared the advantages and disadvantages of the methods and the future development is prospected.

6-benzylaminopurine exposure induced development toxicity and behaviour alteration in zebrafish (Danio rerio)

6-benzylaminopurine (6-BA) is one of the first synthetic hormones and has been widely used in fruit cultivation, gardening and agriculture. However, excessive use of 6-BA will cause potential harm to the environment and humans. Therefore, our research focused on assessing the impact of 6-BA on the development and neurobehavior of zebrafish. The results showed that 6-BA had little effect on the embryos from 2 hpf to 10 hpf. However, delayed development, decreased survival and hatchability were observed under 30 and 40 mg/L 6-BA from 24 hpf. 6-BA also reduced surface tension of embryonic chorions at 24 hpf. In addition, 6-BA caused abnormal morphology and promoted the accumulation of oxidative stress. Transcription of genes in connection with development and oxidative stress was also strikingly altered. Results of movement assay showed that zebrafish were less active and their behavior was significantly inhibited under the 20 and 30 mg/L 6-BA treatments. Locomotion-related genes th and mao were down-regulated by gradient, while the transcription of dbh was upregulated at a low concentration (2 mg/L) but decreased as the concentration increased. Moreover, 6-BA exposure caused increased arousal and decreased sleep. Sleep/wake related genes hcrt and hcrtr2 were upregulated, but decreased at 30 mg/L, while the mRNA level of aanat2 was reduced in a concentration-dependent manner. To sum up, our results showed that 6-BA induced developmental toxicity, promoted the accumulation of oxidative stress, and damaged locomotion and sleep/wake behavior.

Organophosphorus Pesticide Multiresidues in Commercialized Asian Rice

The organophosphorus pesticides (OPPs) commonly used in agricultural practices can pose a risk of potential exposure to humans via food consumption. We describe an analytical method for solid-phase extraction coupled with high-performance liquid chromatography-diode array detector (SPE-HPLC-DAD) for the detection of OPPs (quinalphos, diazinon, and chlorpyrifos) in rice grains. The isolation of targeted residues was initiated with double extraction before SPE-HPLC-DAD, crucially reducing matrix interferences and detecting a wide range of multiple residues in rice grains. Coefficients of 0.9968 to 0.9991 showed a strong linearity, with limits of detection and quantification ranging from 0.36 to 0.68 µg/kg and from 1.20 to 2.28 µg/kg, respectively. High recoveries (80.4-110.3%) were observed at 3 spiking levels (50, 100, and 200 µg/kg), indicating good accuracy. The relative standard deviations of all residues (0.19-8.66%) validated the method precision. Sample analysis of 10 rice grain types (n = 30) available in the Asian market revealed that quinalphos, diazinon, and chlorpyrifos at concentrations of 1.08, 1.11, and 1.79 µg/kg, respectively, remained far below the maximum residue limits (0.01-0.5 mg/kg). However, regular monitoring is necessary to confirm that multiresidue occurrence remains below permissible limits while controlling pests. Environ Toxicol Chem 2020;39:1908-1917. © 2020 SETAC.

Dissipation Dynamic and Final Residues of Oxadiargyl in Paddy Fields Using High-Performance Liquid Chromatography-Tandem Mass Spectrometry Coupled with Modified QuEChERS Method

Oxadiargyl, which binds to the protoporphyrinogen oxidase IX to exhibit herbicide activity, is mainly used in the prevention of certain perennial broadleaved and grass weeds during the preemergence of rice in paddy fields. However, oxadiargyl affects the germination and seedling growth of rice, causing damage to the plant and reducing rice yield. Hence, monitoring fate and behaviour of oxadiargyl in rice paddy fields is of great significance. A modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) sample preparation method coupled with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was established in paddy water, paddy soil, rice straw, paddy hull, and brown rice. We validated this method for the first time in the analysis of the dissipation dynamic and residues of oxadiargyl over two years (2015⁻2016) at three sites in China. The average recoveries of oxadiargyl ranged from 76.0 to 98.8%, with relative standard deviations of 3.5⁻14.0%. The dissipation curves for paddy soil fit to a first-order kinetic equation, revealing that oxadiargyl degraded rapidly in paddy soil with half-lives (t_1/2) of 4.5⁻7.6 days. The final oxadiargyl residues in all samples remained below the detection limit and the maximum residue limit in China (0.02 mg kg^-1) and Japan (0.05 mg kg^-1) during the harvesting dates and were not detected in rice straw.

Multi-pesticides residue analysis of grains using modified magnetic nanoparticle adsorbent for facile and efficient cleanup

A facile, rapid sample pretreatment method was developed based on magnetic nanoparticles for multi-pesticides residue analysis of grains. Magnetite (Fe₃O₄) nanoparticles modified with 3-(N,N-diethylamino)propyltrimethoxysilane (Fe₃O₄-PSA) and commercial C18 were selected as the cleanup adsorbents to remove the target interferences of the matrix, such as fatty acids and non-polar compounds. Rice was used as the representative grain sample for method optimization. The amount of Fe₃O₄-PSA and C18 were systematically investigated for selecting the suitable purification conditions, and the simultaneous determination of 50 pesticides and 8 related metabolites in rice was established by liquid chromatography-tandem mass spectrometry. Under the optimal conditions, the method validation was performed including linearity, sensitivity, matrix effect, recovery and precision, which all satisfy the requirement for pesticides residue analysis. Compared to the conventional QuEChERS method with non-magnetic material as cleanup adsorbent, the present method can save 30% of the pretreatment time, giving the high throughput analysis possible.

Dissipation and Residue Level of Thifluzamide in Rice Field Ecosystem

An efficient modified QuEChERS method combined with high performance liquid chromatography-tandem mass spectrometry detection (HPLC-MS/MS) was established and evaluated for the residue analysis of thifluzamide in rice grain, husk, straw, seedling, paddy water, and soil. Thifluzamide residues were extracted with acetonitrile, cleaned up with primary secondary amine (PSA), and then determined by HPLC-MS/MS. The fortified recoveries were 76%–106% with RSDs of 3%–13%. The results of the supervised field trials at two experiment sites showed that thifluzamide dissipated rapidly in paddy fields, and the half-lives in paddy water, soil, and rice seedling were 0.3–0.6 d, 1.8–3.6 d, and 4.3–13.9 d, respectively. At harvest time, when the preharvest interval (PHI) was set as 21 d, the final residues of thifluzamide in rice grains were below the maximum residue limit (MRL) of 0.5 mg/kg set by Japan, whereas the final residues in rice husk and straw were still high (the highest value reached 1.36 mg/kg in rice husk and 0.83 mg/kg in rice straw). The results indicated that the highest residue in rice grain was 0.23 mg/kg when PHI was 21 d, and only 6.9–11.0% of acute risk quotient of thifluzamide was occupied by the dietary daily intake in Chinese population consuming rice.

Residues of the fungicide epoxiconazole in rice and paddy in the Chinese field ecosystem

BACKGROUND

Epoxiconazole is extensively used as fungicide in cereals, grapes and other crops worldwide. Rice is one of the world's most important food crops. Many people who depend on rice for their food live in Asia. A method employing liquid chromatography-tandem mass spectrometry was developed for determination of epoxiconazole in brown rice, straw, rice hull, paddy water and soils. Epoxiconazole residues in rice hull, brown rice, straw and soil were also determined.

RESULTS

The limit of quantitation was set at 0.01 mg kg(-1) for the matrices studied. Epoxiconazole degradation in straw, paddy water and soil was studied. The epoxiconazole residues in brown rice, straw, hull and paddy soil were determined. Concurrent recoveries were between 89.2 and 104.1%, with relative standard deviations ranging from 4.6 to 14.4% at three fortification levels between 0.01 and 5.0 mg kg(-1). The half-lives in straw, paddy water and soils were found to be 4.7-5.9, 2.9-6.0 and 2.9-6.4 days respectively. The maximum residues in brown rice, straw, hull and paddy soil samples were 0.18, 2.47, 2.54 and 0.09 mg kg(-1) respectively.

CONCLUSION

Compared with the maximum residue levels (MRLs) for epoxiconazole in rice that have been set by the European Union (0.1 mg kg(-1)) and by China (0.5 mg kg(-1)), the epoxiconazole residue on rice at an application rate of 112.5 g AI ha(-1) with two applications at an interval of 7 days, and with a 28 day preharvest interval (PHI), is below the MRL, and thus the use of epoxiconazole is considered to be safe. Epoxiconazole should be applied correctly, according to good agricultural practice, using only the recommended amounts, frequencies and appropriate PHI.

Validation of a multiclass multiresidue method and monitoring results for 210 pesticides in fruits and vegetables by gas chromatography-triple quadrupole mass spectrometry

A rapid, sensitive, accurate and reliable multiresidue method for the identification and quantification of 210 relevant pesticides in four representative fruit and vegetable commodities (tomato, potato, spring onion and orange) has been developed and validated by gas chromatography in tandem with triple quadrupole mass spectrometry. The method has been fully validated and applied to 292 samples from different countries. Prior to instrumental analysis, an extraction procedure based on a sample extraction of multiclass analytes, using the ethyl acetate method was employed. Mass spectrometric conditions were individually optimized for each compound in the selected reaction monitoring (SRM) mode to achieve maximum sensitivity. The pesticides were separated in less than 25 min. This was followed by an exhaustive control of the retention times. The Retention Time Locking Method was applied, working at a constant pressure throughout the analysis. System maintenance was reduced by using a purged capillary flow device that provided backflush capabilities by reversing column flow immediately after elution of the last compound of interest. Istotopically labelled internal standards were employed to improve the quality of the analytical results.