Determination of strobilurin fungicide residues in fruits and vegetables by nonaqueous micellar electrokinetic capillary chromatography with indirect laser‐induced fluorescence

A nonaqueous micellar electrokinetic capillary chromatography method with indirect LIF was developed for the determination of strobilurin fungicide residues in fruits and vegetables. Hydrophobic CdTe quantum dots (QDs) synthesized in aqueous phase were used as background fluorescent substance. The BGE solution, QD concentration, and separation voltage were optimized to obtain the best separation efficiency and the highest signal intensity. The optimal BGE solution consists of 40 mM phosphate, 120 mM sodium dodecyl sulfate, 15% v/v water and 15% v/v hydrophobic CdTe QDs in formamide, of which apparent pH is 9.5. The optimized separation voltage is controlled as 25 kV. The resultant detection limits of azoxystrobin, kresoxim‐methyl, and pyraclostrobin are all 0.001 mg/kg, their linear dynamic ranges are 0.005–2.5 mg/kg, and the recoveries of the spiked samples are 81.7–96.1%, 86.5–95.7%, and 87.3–97.4%, respectively. This method has been proved to be sensitive enough to detect the aforementioned fungicides in fruits and vegetables at the maximum residue limits.     

Application of solid-phase extraction and liquid chromatography-mass spectrometry to the determination of neonicotinoid pesticide residues in fruit and vegetables

A rapid and simple method for simultaneous analysis of four neonicotinoid insecticides including acetamiprid, imidacloprid, thiacloprid and thiamethoxam in fruit and vegetable matrices has been developed. For instance, ready-to-use cartridges filled with a macroporous diatomaceous material were used to extract in a single step insecticide residues with dichloromethane from aqueous-acetone extracts of fruits and vegetables. The eluate was evaporated, the residue redissolved with methanol and then analyzed by liquid chromatography-mass spectrometry in the electrospray ionization (ESI) positive mode. Average recoveries of the four pesticides were between 74.5 and 105% at both spiking levels 0.1 and 1.0 mg kg(-1) in peach, pear, courgette, celery and apricot. Relative standard deviations (RSDs) were less than 10% for all of the recovery tests. The calculated limits of quantitation (LOQs) (0.1-0.5 mg kg(-1)) were equal or lower then the maximum residue limits (MRLs) established by European legislation (0.1-0.5 mg kg(-1)). The proposed method is fast, easy to perform and could be utilized for monitoring of pesticides residues.     

毛细管电泳在线电推扫测定蔬菜中3种氯化烟碱类农药残留

以采用电动进样模式的毛细管电泳在线电推扫技术建立了测定蔬菜中吡虫啉、啶虫脒和噻虫嗪残留的新方法.研究了缓冲液浓度、pH值、十二烷基硫酸钠浓度、分离电压和进样量对峰高的影响,优化后缓冲液为40 mmol/L硼酸盐、60 mmol/L十二烷基硫酸钠、pH 7.8,进样电压10 kV,进样时间120 s,分离电压25 kV.在此条件下,吡虫啉、啶虫脒和噻虫嗪的富集倍数可达626,788和443倍;检出限分别为5.6,2.9和2.5 μg/kg;相对标准偏差为1.65%,1.92%和0.96%;平均加标回收率为87.4%～102.5%,95.3%～103.1%和78.7%～93.9%.本方法可满足相关标准中的残留限量要求,已用于蔬菜中这3种农药残留的检测.     

固相萃取-液相色谱测定复杂基质蔬菜中9种烟碱类残留

建立了韭菜、洋葱、大蒜等复杂基质蔬菜样品中呋虫胺、烯啶虫胺、氟啶虫酰胺、噻虫嗪、吡虫啉、噻虫胺、氯噻啉、啶虫脒、噻虫啉9种烟碱类农药残留的液相色谱检测方法.对比了几种常用溶剂的提取效率以及固相萃取材料对韭菜、洋葱样品中干扰基质的去除效果.研究结果表明,样品经微波处理后,用乙腈提取,Envi-Carb/PSA固相萃取柱净...     

Determination of five quinolone antibiotic residues in foods by micellar electrokinetic capillary chromatography with quantum dot indirect laser-induced fluorescence

A new assay was developed for the determination of five quinolone antibiotic residues in foods, loxacin, enrofloxacin, ciprofloxacin, lomefloxacin, and norfloxacin, by micellar electrokinetic capillary chromatography with indirect laser-induced fluorescence, in which cadmium telluride quantum dots were used as a fluorescent background substance. Some factors that affected the peak height and the resolution were examined. The optimized running buffer was composed of 20 mM SDS, 7.2 mg/L quantum dots, and 10 mM borate at pH 8.8. The separation voltage was 20 kV. Under these conditions, five quinolone antibiotic residues were separated successfully within 8 min. The detection limits ranged from 0.003 to 0.008 mg/kg; the linear dynamic ranges were all 0.01?～?10 mg/kg; and the average recoveries of the spiked samples were 81.4?～?94.6 %. The assay can meet the requirement of maximum residue limits to these five quinolone antibiotics in the regulations of the European Union and Japan and has been applied for determining their residues in animal-derived food.

毛细管电泳-量子点间接激光诱导荧光检测5种食品防腐剂

以碲化镉量子点为荧光背景物质,建立了毛细管电泳-间接激光诱导荧光检测食品中对羟基苯甲酸丙酯、脱氢乙酸钠、山梨酸、苯甲酸和丙酸钠含量的方法,紫外吸收很弱的丙酸钠在本方法中显示为正峰,可被有效检出.研究了碲化镉量子点浓度、背景电解质浓度、pH值、分离电压对分析物峰高和迁移时间的影响.在最佳条件下,对羟基苯甲酸丙酯、脱氢乙酸钠、山梨酸、苯甲酸和丙酸钠在8.5 min内得到分离,检出限分别为0.21,0.32,0.50,0.30和0.36 mg/L,相对标准偏差分别为3.9％,2.1％,2.5％,1.9％和2.3％,平均加标回收率分别为96.8％,93.4％,96.3％,98.1％和99.1％.本方法的检出限及线性范围均优于文献报道结果,对食品中这5种防腐剂检测的结果与高效液相色谱法结果一致.     

液相色谱法检测水果蔬菜中的烟碱类农药残留

建立了果蔬样品中5种烟碱类农药(噻虫嗪、吡虫啉、啶虫脒、噻虫啉、噻虫胺)残留的液相色谱快速检测方法。样品采用乙腈提取,浓缩,水转溶后经ENVI-18固相萃取柱净化,0.02 mol/L NaOH预淋洗除去柱上中等极性干扰物,100%乙腈1 mL洗脱5种烟碱类残留,反相高效液相色谱-二极管阵列检测器检测。在黄瓜空白基质中0.1~1.0 mg/kg的加标浓度范围内,5种农药的回收率为50.8%~108.9%,相对标准偏差(RSD)小于15%;而苹果、梨、香蕉、西红柿和韭菜空白基质在0.1~1.0 mg/kg添加水平下,5种农药的回收率均大于80%,RSD小于11%。所测试的6种果蔬样品中噻虫嗪、噻虫胺、吡虫啉的检出限(LOD)为0.01~0.02 mg/kg,啶虫咪和噻虫啉的LOD为0.03~0.05 mg/kg,方法可满足水果蔬菜中烟碱类农药多残留分析的要求。     

Simultaneous determination of residues in pollen and high-fructose corn syrup from eight neonicotinoid insecticides by liquid chromatography–tandem mass spectrometry

The neonicotinoids have recently been identified as a potential contributing factor to the sudden decline in adult honeybee population, commonly known as colony collapse disorder (CCD). To protect the health of honeybees and other pollinators, a new, simple, and sensitive liquid chromatography-electrospray ionization mass spectrometry method was developed and validated for simultaneous determination of eight neonicotinoids, including acetamiprid, clothianidin, dinotefuran, flonicamid, imidacloprid, nitenpyram, thiacloprid, and thiamethoxam, in pollen and high-fructose corn syrup (HFCS). In this method, eight neonicotinoids, along with their isotope-labeled internal standards, were extracted from 2 g of pollen or 5 g of HFCS using an optimized quick, easy, cheap, effective, rugged, and safe extraction procedure. The method limits of detection in pollen and HFCS matrices were 0.03 ng/g for acetamiprid, clothianidin, dinotefuran, imidacloprid, thiacloprid, and thiamethoxam and ranged between 0.03 and 0.1 ng/g for nitenpyram and flonicamid. The precision and accuracy were well within the acceptable 20 % range. Selectivity, linearity, lower limit of quantitation, matrix effect, recovery, and stability in autosampler were also evaluated during validation. This validated method has been used successfully in analyzing a set of pollen and HFCS samples collected for evaluating potential honeybee exposure to neonicotinoids.     

Analysis of nicotinoid insecticides residues in honey by solid matrix partition clean-up and liquid chromatography-electrospray mass spectrometry

An analytical method for the routine simultaneous determination of four nicotinoid insecticides (acetamiprid, imidacloprid, thiacloprid and thiamethoxam) in commercial multifloral honey was developed. Fortified honey samples, dissolved in water, were cleaned up through Extrelut NT20 column and, finally, insecticides were eluted with dichloromethane. The eluate was evaporated, the residue redissolved in methanol and then analyzed by LC-ESI(+)-MS. Average recoveries of the four analytes were in the range of 76% and 99% at both spiking levels 0.1 and 1.0 mg kg(-1). Relative standard deviations (RSDs) were less than 10% for all of the recovery tests. The detection limits (LODs) of the method ranged from 0.01 to 0.1 mg kg(-1) for the different insecticides studied. The developed method is linear over the range assayed, 0.5-5.0 microg mL(-1), with linear correlation coefficients higher than 0.9993.     

Biotin-modified glutathione as a functionalized coating for bioconjugation of CdTe-based quantum dots

In this study, biotin-conjugated glutathione was synthesized using peptide bonding of the biotin carboxy group and amino group of the γ-glutamic acid to prepare an alternative coating for CdTe quantum dots (QDs). This type of coating combines the functionality of the biotin with the fluorescent properties of the QDs to create a specific, high-affinity fluorescent probe able to react with avidin, streptavidin and/or neutravidin. Biotin-functionalized glutathione-coated CdTe QDs were prepared by a simple one-step method using Na? TeO? and CdCl?. Obtained QDs were separated from the excess of the biotin-conjugated glutathione by CE employing 300?mM borate buffer with pH 7.8 as a background electrolyte. The detection of sample components was performed by the photometric detection at 214?nm and LIF employing Ar? ion laser (488?nm).     

Sensitive determination of thiamethoxam, imidacloprid and acetamiprid in environmental water samples with solid-phase extraction packed with multiwalled carbon nanotubes prior to high-performance liquid chromatography

This paper describes a novel method for sensitive determination of thiamethoxam, imidacloprid and acetamiprid based on solid-phase extraction with multiwalled carbon nanotubes as the packed materials. Factors that maybe influence the enrichment efficiency, such as sample flow rate, sample pH, and sample volume, were investigated in detail. Under the optimized conditions, the detection limits of thiamethoxam, imidacloprid and acetamiprid were 6.1, 5.4 and 6.7 ng L⁻¹, respectively. The experimental results indicated that there was good linearity (R ²>0.9993) over the range of 0.08~100 ng mL⁻¹ and good reproducibility with the relative standard deviations over the range of 0.7~1.1% (n=6). The proposed method has been applied to the analysis of real-world water samples, and satisfactory achievements were obtained. The average spiked recoveries were in the range of 87.5~109.8%. All the results indicated that the proposed method could be used for the simultaneous determination of the three pesticides in environmental water samples at trace levels.     

在线固相萃取-超高效液相色谱/串联质谱法测定水中新烟碱类杀虫剂

采用在线固相萃取-超高效液相色谱/串联质谱技术建立了水中啶虫脒、噻虫胺、吡虫啉、噻虫啉、噻虫嗪、呋虫胺及烯啶虫胺7种新烟碱类杀虫剂的检测方法。样品滤膜过滤后,经HLB Dierect Connect HP在线固相萃取小柱富集纯化,以ACQUITY UPLC BEH C₁₈为分析柱串联质谱进行检测,外标法定量。在线富集水样中新烟碱类物质在5.0~200 ng/L范围内线性关系良好,相关系数R²均大于0.99;检出限为0.30~2.92 ng/L,相对标准偏差均小于10%。该法可用于保障水环境安全、及时提供污染信息。     

Long-term exposure to CdTe quantum dots causes functional impairments in live cells

Several studies suggested that the cytotoxic effects of quantum dots (QDs) may be mediated by cadmium ions (Cd2+) released from the QDs cores. The objective of this work was to assess the intracellular Cd2+ concentration in human breast cancer MCF-7 cells treated with cadmium telluride (CdTe) and core/shell cadmium selenide/zinc sulfide (CdSe/ZnS) nanoparticles capped with mercaptopropionic acid (MPA), cysteamine (Cys), or N-acetylcysteine (NAC) conjugated to cysteamine. The Cd2+ concentration determined by a Cd2+-specific cellular assay was below the assay detection limit (<5 nM) in cells treated with CdSe/ZnS QDs, while in cells incubated with CdTe QDs, it ranged from approximately 30 to 150 nM, depending on the capping molecule. A cell viability assay revealed that CdSe/ZnS QDs were nontoxic, whereas the CdTe QDs were cytotoxic. However, for the various CdTe QD samples, there was no dose-dependent correlation between cell viability and intracellular [Cd2+], implying that their cytotoxicity cannot be attributed solely to the toxic effect of free Cd2+. Confocal laser scanning microscopy of CdTe QDs-treated cells imaged with organelle-specific dyes revealed significant lysosomal damage attributable to the presence of Cd2+ and of reactive oxygen species (ROS), which can be formed via Cd2+-specific cellular pathways and/or via CdTe-triggered photoxidative processes involving singlet oxygen or electron transfer from excited QDs to oxygen. In summary, CdTe QDs induce cell death via mechanisms involving both Cd2+ and ROS accompanied by lysosomal enlargement and intracellular redistribution.     

固相萃取-高效液相色谱同时测定大米中的4种烟碱农药残留量

建立了高效液相色谱法同时测定大米样品中呋虫胺、噻虫胺、吡虫啉、吡虫清4种烟碱农药残留量的检测方法,对4种烟碱农药在ENVI-Florisil和Carb复合固相萃取柱上的保留行为进行了研究。样品用乙腈提取,固相萃取净化,HPLC-DAD分离检测,外标法定量。峰面积与标准溶液浓度在0.1～1.0 mg/L范围内呈良好的线性关系,相关系数大于0.9996。样品加标回收率为75.5%～96.0%,相对标准偏差为0.49%～4.36%(n=6),检出限达到0.004 mg/kg。     

Ethanol-ammonium sulfate system based modified quick,easy, cheap,effective, rugged,and safe method for the determination of four neonicotinoid pesticide and metabolite residues in two canned fruits

As the pesticide and its metabolite residues in processed fruits could become a significant route of human exposure. The work presented herein focuses on developing a feasible quick, easy, cheap, effective, rugged, and safe method with improved extraction and cleanup system for the determination of imidacloprid, acetamiprid, thiamethoxam, and clothianidin (a metabolite of thiamethoxam) in canned fruits. The low toxic solvent ethanol was used to extract the analytes, and ammonium sulfate was used to promote phase separation. Moreover, the carboxylated multi-walled carbon nanotube acted as the clean-up sorbent for the removal of high solubility impurities. The proposed method was validated with fortified real samples at different concentration levels (20–200 μg/kg). Recoveries obtained from three spiked levels (20, 50, and 200 μg/kg) ranged from 74.9 to 86.4% with relative standard deviations of the intra-day and inter-day in the range of 0.8–5.5 and 2.0–7.1%, respectively. The limits of detection ranged from 0.2 to 0.5 and 0.2 to 0.6 μg/kg for orange and peach, respectively. The results demonstrated that the proposed method could be considered appropriate, and comparatively lower toxic for the analysis of neonicotinoid pesticide residues in canned fruit.     

在线净化-液相色谱-串联质谱法测定茶叶中5种烟碱类农药残留

建立了在线净化-液相色谱-串联质谱测定茶叶中吡虫啉、啶虫脒、噻虫啉、噻虫嗪和噻虫胺5种常见烟碱类农药残留量的方法。样品经水浸泡、乙腈提取和在线净化后,用液相色谱-串联质谱测定。结果表明,本方法对5种烟碱类农药的定量限均为0.01 mg/kg。5种烟碱类农药在1.0~10 μ g/L范围内具有良好的线性关系,相关系数均大于0.998。在0.01、0.02和0.05 mg/kg的添加水平下,回收率为68.0%~113.2%,相对标准偏差为3.2%~7.6%。本方法简便、快速、准确,适用于茶叶样品中烟碱类农药残留量的检测。     

Development of validated LC-MS/MS method for imidacloprid and acetamiprid in parsley and rocket and evaluation of their dissipation dynamics

Fast and efficient method based on quick, easy, cheap, effective, rugged and safe followed by liquid chromatography–tandem mass spectrometry for acetamiprid and imidacloprid residues determination in parsley and rocket was developed and validated. Linearity (R²) ranged from 0.996 to 0.999. Accuracy ranged from 95.9 to 99.1%. Precision was <11%. Limit of quantification was 2.8–10.3?µg/kg. Matrix effect was evaluated. Dissipation of acetamiprid and imidacloprid in parsley and rocket was investigated under open field conditions. The dissipation behavior of both compounds followed first-order kinetics. Half-lives (t_1/2) were 2.68 and 4.24 days with dissipation rate (k) values of 0.25 and 0.165 days^?1 for acetamiprid; 0.24 (in parsley) and 0.25 (in rocket) days^?1 with k values of 0.636 (in parsley) and 0.718 (in rocket) days for imidacloprid. Preharvest interval values were 5.53 and 1.42 days for acetamiprid; 2.5 and 0.49 days for imidacloprid in parsley and rocket, respectively. Residues of both compounds were searched in real samples. None of the real samples violated maximum residues limits of the European Commission regulations.     

An Electrochemical Sensor Based on Electropolymerization of ß‐Cyclodextrin and Reduced Graphene Oxide on a Glassy Carbon Electrode for Determination of Neonicotinoids

An electrochemical sensor of glassy carbon electrode modified with reduced graphene oxide and β‐cyclodextrin (GCE/rGO/β‐CD) was developed as an effective alternative in the determination of neonicotinoid insecticides, imidacloprid, clothianidin and thiamethoxam, in honey samples. The peak current variation obtained with the proposed sensor was higher compared to the bare GCE in all the analytes. In the determination of imidacloprid the response increased by 1300 %, clothianidin by 670 % and thiametoxam by 630 %. In addition, the optimization of the experimental conditions provided the construction of a sensor with greater sensitivity. The study of interferers showed that inorganic ions (Ca²⁺, Mg²⁺, Fe²⁺, K⁺, Na⁺, e NH₄⁺) and other insecticides (acetamiprid and dinotefuran) did not influence the reduction of imidacloprid, clothianidin and thiamethoxam. The determination of imidacloprid, clothianidin and thiamethoxam in honey samples exhibited recovery values within the EPA range (between 107.75 and 116 %). In conclusion, the developed sensor GCE/rGO/β‐CD proved to be an effective alternative in the determination of neonicotinoid insecticides in honey samples.     

Liquid chromatography–tandem mass spectrometry analysis of neonicotinoid pesticides and 6-chloronicotinic acid in environmental water with direct aqueous injection

An efficient, high throughput and cost-effective direct aqueous injection approach for the analysis of neonicotinoid pesticides and a common metabolite in environmental water has been described here. The method determines eight neonicotinoid pesticides (acetamiprid, clothianidin, dinotefuran, flonicamid, imidacloprid, nitenpyram, thiacloprid, thiamethoxam) and 6-chloronicotinic acid (a common metabolite of the first generation neonicotinoids, acetamiprid, imidacloprid, nitenpyram and thiacloprid) without any sample enrichment/cleanup steps. The method detection limits are 2–8 ng/L for the neonicotinoids and 93 ng/L for 6-chloronicotinic acid. The performance of the QTRAP^®5500 mass spectrometer was compared against a 4000QTRAP^®, and a QTRAP^®6500, to provide insights for future method transfer among different generations of instrumentations. Critical mass spectrometric parameters such as collision energy were quite consistent among the three instruments evaluated. However, increased chemical background levels for some target compounds on the more sensitive instruments were observed. The application of differential ion mobility spectrometry combined with tandem mass spectrometry was demonstrated to have great potential in reducing chemical background and/or isobaric interferences inherited in sample matrices. This ISO 17025 accredited method was employed to quantitate neonicotinoids in Ontario stream water samples. Good correlation for analytical results of this direct aqueous injection approach and a previously published solid phase extraction approach warrant high confidence in data quality.     

Determination of neonicotinoid pesticides residues in agricultural samples by solid-phase extraction combined with liquid chromatography-tandem mass spectrometry

This work reports a new sensitive multi-residue liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for detection, confirmation and quantification of six neonicotinoid pesticides (dinotefuran, thiamethoxam, clothiandin, imidacloprid, acetamiprid and thiacloprid) in agricultural samples (chestnut, shallot, ginger and tea). Activated carbon and HLB solid-phase extraction cartridges were used for cleaning up the extracts. Analysis is performed by LC-MS/MS operated in the multiple reaction monitoring (MRM) mode, acquiring two specific precursor-product ion transitions per target compound. Quantification was carried by the internal standard method with D(4)-labeled imidacloprid. The method showed excellent linearity (R(2)≥0.9991) and precision (relative standard deviation, RSD≤8.6%) for all compounds. Limits of quantification (LOQs) were 0.01 mg kg(-1) for chestnut, shallot, ginger sample and 0.02 mg kg(-1) for tea sample. The average recoveries, measured at three concentrations levels (0.01 mg kg(-1), 0.02 mg kg(-1) and 0.1 mg kg(-1) for chestnut, shallot, ginger sample, 0.02 mg kg(-1), 0.04 mg kg(-1) and 0.2 mg kg(-1) for tea sample), were in the range 82.1-108.5%. The method was satisfactorily validated for the analysis of 150 agricultural samples (chestnut, shallot, ginger and tea). Imidacloprid and acetamiprid were detected at concentration levels ranging from 0.05 to 3.6 mg kg(-1).