Transfer assessment of fipronil residues from feed to cow milk

Fipronil, a phenylpyrazole insecticide introduced for pest control on a broad range of crops, can also affect non-target insects such as honeybees. More widely, non-target environment such as milk produced by dairy cows fed with maize silage from treated seeds (=silage T) can be affected. To assess the potential transfer of fipronil residues (sulfone, sulfide, fipronil, desulfinyl and amide), a methodology including gas chromatography coupled with tandem mass spectrometry (GC-MS/MS) analysis was developed and validated according to the 2002/657/EC decision, in order to reach a level of quantification below 0.1 μg L⁻¹ in milk and 0.1 μg kg⁻¹ in plants. Twelve dairy cows were fed with silage T during 4 months. Concentration of fipronil in treated seeds was estimated at 1 g kg⁻¹, whereas silage from these seeds contained 0.30 ± 0.05 μg kg⁻¹ of dry material of fipronil, 0.13 ± 0.03 μg kg⁻¹ of dry material of sulfone. Sulfide residues were below the limit of quantification. Silage from untreated seeds (=silage U) presented traces of fipronil and sulfone, respectively at 0.04 ± 0.06 and 0.02 ± 0.03 μg kg⁻¹ of dry material. Contribution of fipronil residues from supplies was insignificant. During administration of silage T, only sulfone residues were quantified in milk. The average concentration was 0.14 ± 0.05 μg L⁻¹. Before and after administration, sulfone residues were detected but not quantifiable (<0.025 μg L⁻¹). Our results suggest a transfer of fipronil from feed to milk under its sulfone form. Moreover, traces of fipronil residues in maize U, soya, wheat and straw show a diffuse contamination of this pesticide in the environment.     

荧光标记法研究鱼类GABA受体与Ro7-1986/1和Fipronil的相互作用

以苯二氮卓类化合物Ro7-1986/1和氟虫腈(Fipronil)分别与异硫氰酸荧光素(FITC)反应合成了2种γ-氨基丁酸(GABA)受体的配体荧光复合物,即FITC-Ro7-1986/1(简称FITC-Ro7)和FITC-Fipronil;利用傅里叶变换红外光谱(FTIR)和核磁共振氢谱(1H NMR)等手段对其结构进行了表征.以2种荧光配体为探针,采用荧光标记法研究了Ro7-1986/1和Fipronil与鳙鱼(Hypophthalmichthys nobilis)脑内GABA受体的相互作用,得到了亲和常数Kd和最大结合量[RT].同时考察了GABA对Ro7-1986/1与受体相互作用的影响.研究结果表明,Ro7-1986/1和Fipronil与受体的亲和常数Kd分别为(67±5)nmol/L和(346±6)nmol/L;最大结合量[RT]分别为(13.8±1.8)pmol/mg protein和(40.6±3.5)pmol/mg protein;GABA促进了Ro7-1986/1与受体的结合,进一步的研究结果表明,鱼类与哺乳动物脑中GABA受体结构相似;相对于哺乳动物,苯吡唑类杀虫剂Fipronil对鱼类GABA的亲和力较高.     

Determination of Fipronil in Acetamiprid Formulation by Attenuated Total Reflectance-Mid-Infrared Spectroscopy Combined with Partial Least Squares Regression

There is a high demand for rapid determination of fipronil in pesticide preparations because it has been restricted and even prohibited in many countries. An infrared-based methodology was developed for this analyte in acetamiprid formulations by attenuated total reflectance mid-infrared spectroscopy. The quantitative calibration models of fipronil were established by partial least squares regression. The determination coefficients (R²) of the model were above 0.99 while both the root mean square error of prediction and root mean square error of calibration were below 0.0011, which showed the partial least squares model accurately predicted fipronil concentrations in acetamiprid. The accuracy was further demonstrated by comparison with another two models' results of low (<1.0%, w/w) and high concentration sample sets (1.0%–4.5%, w/w). These results demonstrate the potential of infrared spectroscopy to quickly detect fipronil in acetamiprid.     

大白菜、甘蓝和西兰花中锐劲特残留量气相色谱分析方法的研究

建立了大白菜、甘蓝和西兰花3种蔬菜中的锐劲特残留量分析方法。以乙腈为提取溶剂,使用弗罗里硅土SPE小柱净化,最后利用GC-ECD进行检测,仪器最小检测量为5×10-13g,最低检出浓度为0.0005 mg/kg。在大白菜中平均回收率为85.11%~89.81%,RSD为3.8%~6.8%;甘蓝中平均回收率为91.39%~102.92%,RSD为5.2%~8.3%;西兰花中平均回收率达到91.92%~101.64%,RSD为4.5%~6.8%。     

Reagentless Photochemically-Induced Fluorimetric Determination of Fipronil by Sequential-Injection Analysis

This paper deals with the photo-induced fluorimetric determination of the insecticide fipronil using a sequential-injection flow assembly provided with an on-line photoreactor. The fluorescent photoproduct generated after UV irradiation for 20 s of the insecticide at 0.01 M NaOH solution is monitored at 245/450 nm/nm (λ_exc/λ_em). A detection limit of 0.17 µg mL^?1 and a sample throughput of 18 samples per hour were obtained. The proposed method was satisfactorily applied to the determination of the analyte in phytosanitary and veterinary products with minimum pretreatment. In addition, a recovery study was performed in all the analyzed samples, observing recoveries between 95 and 100%, with R.S.D. lower than 3% in all cases.     

Determination of fipronil and its major metabolites in vegetables,fruit and soil using QuEChERS and gas chromatography-mass spectrometry

A rapid, simple and selective gas chromatography with mass spectrometric detection (GC-MS) method was developed and validated for simultaneously determining fipronil and its three major metabolites in vegetables, fruit and soil. The fipronil residues were extracted using QuEChERS technique with ethyl acetate and then were purified by dispersive solid phase extraction (d-SPE) cleanup for cabbage, cauliflower, okra, tomato, grapes and soil. The linearity of the analytical response across the studied range of concentrations (0.01–0.5?µg?mL^?1) was excellent, obtaining correlation coefficients higher than 0.999. The average recoveries of the pesticide from all matrixes ranged from 86 to 112%, for fortification levels of 0.01, 0.05 and 0.1?µg?g^?1. The precision values associated with the analytical method, expressed as RSD values, were less than 10.15% for the pesticide in all matrixes. This method can be used to evaluate environmental residues and the safety of agricultural products.     

Rapid and sensitive detection of fipronil and its metabolites in edible oils by solid‐phase extraction based on humic acid bonded silica combined with gas chromatography with electron capture detection

Solid‐phase extraction based on humic acid bonded silica followed by gas chromatography with electron capture detection was developed to determine fipronil and its metabolites in edible oil. To achieve the best extraction performance, we systematically investigated a series of solid‐phase extraction parameters. Under the optimized conditions, the method was validated according to linearity, recovery, and precision. Good linearities were obtained with R² more than 0.9996 for all analytes. The limits of detection were between 0.3 and 0.5 ng/g, and the recoveries ranged from 83.1 to 104.0% at three spiked concentrations with intra‐ and interday relative standard deviation values less than 8.7%. Finally, the proposed method was applied to determine fipronil and its metabolites in 11 edible oil samples taken from Wuhan markets. Fipronil was detectable in four samples with concentrations ranging from 3.0 to 5.2 ng/g. In China, the maximum residue limits of fipronil in some vegetables and maize are 20 and 100 ng/g (GB/T 2763‐2014), respectively. The residues of fipronil and its metabolites in commercial edible oils might exhibit some potential threat to human health as a result of high consumption of edible oil as part of daily intake.     

植物性食品中锐劲特残留量的检测方法研究

研究了测定植物性食品中锐劲特残留的气相色谱方法。试样经丙酮提取,正己烷反萃取,中性氧化铝加少量活性炭柱进行净化,以GC/ECD方式测定,外标法定量。实验表明:试样中添加0.005~0.25 mg.kg-1水平的锐劲特,标准添加回收率为84%~110%,方法检出限为5μg.kg-1。同一样品中6次测定锐劲特残留量的相对标准偏差小于5%。     

Ultraviolet Photo-Induced Fluorescence Followed by Laser Excitation (UV-PIF-LE) for the Determination of Pesticides in Natural Waters

Abstract

A new method was developed for determining trace amounts of pesticides, using an ultraviolet (UV) lamp to obtain photo-induced fluorescent (PIF) compounds, and then using laser excitation (LE) by a tunable source to excite and simultaneously characterize their fluorescence over a short acquisition time using an intensified charge-coupled device camera. This new UV-PIF-LE method was applied to determine isoproturon, oxadiazon, and fipronil in natural waters. This approach represents an improvement on the previously published direct laser photo-induced fluorescent (DL-PIF) approach that utilized the inclusion of a supplementary UV irradiation device in the experimental setup, permitting the separation of the formation and detection steps for the PIF analytes. This evolution improves the selectivity and increases the sensitivity while maintaining a short analysis time. The UV-PIF-LE method gave very good results with satisfactory analytical performance for the determination of the selected pesticides. This approach also demonstrated good reproducibility, with relative square deviation values between 3.3% and 6.3%, for spiked river water and seawater samples with detection limits in the ng mL^?1 range.     

Rapid detection of illicit fipronil in phoxim granules by mid-infrared spectroscopy

In this paper, we use mid-infrared spectroscopy to detect illicit fipronil in phoxim granules by partial least discrimination analysis (PLS-DA). The classification accuracy (CA) of the calibration set and prediction set are both 100.0% with the additive level of fipronil ranges from 0.1% to 5.0%. The results indicate that MIR coupled with chemometric method has the potential in detecting illicit pesticide addition and the proposed method provides a new idea on pesticide quality control.