Changes in eleven pesticide residues in jujube (Ziziphus jujuba Mill.) during drying processing

Processing can concentrate residues or convert residues to more toxic metabolites in food. The residual behavior of 11 pesticides in jujube fruits during four drying processes (freeze-, oven-, sun-, and microwave-drying) was assessed. Jujube samples with residues of dichlorvos, malathion, chlorpyrifos, triadimefon, hexaconazole, myclobutanil, kresoxim-methyl, tebuconazole, epoxiconazole, bifenthrin, and cyhalothrin were obtained from field trials. The degradation rates of pesticides during four drying processes were between 11.4 and 95.1%. Pearson analysis showed that the degradation of pesticide residues in jujube during sun-, oven-, microwave-drying processing was related to vapor pressure and solubility in water of the pesticides. Furthermore, the effects of four drying processes on the processing factors (PFs) were investigated. After freeze-drying, PFs of pesticides were >1, except for chlorpyrifos, suggesting that the dietary exposure risk of pesticides from jujube might be increased if freeze-dried samples were used. After microwave-drying, the PFs of all pesticides were <1, indicating microwave-drying process can significantly reduce 11 pesticide residues in dried jujube.     

Extraction and Enrichment of Pesticides for Analysis using Binary Supercritical Fluid Mixtures

Abstract

To improve the extraction selectivity in analytical supercritical fluid extraction (SFE), binary mixtures of supercritical fluids have been used to selectively produce lipid‐free extracts of trace pesticide residues for chromatographic analysis. Mixtures of nitrogen and HC‐134a have been used in conjunction with carbon dioxide to selectively extract both fortified and incurred residues from a variety of fatty foods using both experimental and commercially‐available extraction instrumentation. Extraction of fortified pesticides in butter fat showed high recoveries for both organo‐chlorine and ‐phosphorus pesticides with recoveries declining for specific pesticide moieties at the 1 ppb spiking level for CO₂/N₂ mixtures. For CO₂ and HC‐134a mixtures, there was poor and little improvement in analyte recovery relative to using neat SC‐CO₂ for fortified organochlorine pesticides in butter fat at the 0.5–5.0 ppm level. However using a CO₂/HC‐134a mixture for organophosphorus pesticides in butter fat improved recoveries (>90%) of the analytes at the 1–3.5 ppm level relative to using neat SC‐CO₂. Excellent recoveries were obtained for incurred organochlorine and ‐phosphorus pesticides from a variety of food products at ppb levels using either CO₂/N₂ or CO₂/HC‐134 mixtures. Results from these and additional experiments suggest that binary fluid mixtures can significantly reduce the need for additional sample cleanup prior to chromatographic analysis, allowing in some cases, direct injection of the extract after dilution into the gas chromatograph.     

有机氯农药、有机磷农药的EIMS、NCIMS和PCIMS质谱

阐述31种农药在3种电离方式：电子轰击质谱(EIMS)、正化学电离质谱(PCIMS)和负化学电离质谱(NCIMS)下的质谱特征和裂解规律，为农药残留的筛选和结构确证奠定基础。分别测定18种有机氯农药、13种有机磷农药的电子轰击质谱(EIMS)，正化学电离质谱(PCIMS)和负化学电离质谱(NCIMS)。在EIMS中，有机氯农药主要产生[M—Cl]^ 、[M—HCl]^ 离子，有机磷农药主要产生磷酸基和磷酸酯基离子；在NCIMS中，[Cl]^-或[HCl2]^-离子是有机氯农药的基峰，有机磷农药主要产生磷酸酯基负离子，某些芳香硫代磷酸酯还可产生重排离子；而在PCIMS中．大多数农药的灵敏度较低．没有观察到质谱。     

基于UPLC-MS/MS检测番茄中10种杀虫剂农药残留

[目的]建立了同时检测番茄中10种杀虫剂残留的分析方法。[方法]采用乙腈提取番茄中的农药有效成分,并在常规QuEChERS吸附剂中添加新型吸附剂(石墨烯和碳纳米管)进行净化,采用超高效液相-质谱联用法(UPLC-MS/MS)分析,对9种吸附剂组合的净化效果进行对比研究。[结果]10种杀虫剂的检出限为1~4μg/kg,定量限为10μg/kg;添加石墨烯和碳纳米管的吸附剂组合,对色素的净化效果优于常规吸附剂,且分层效果好;番茄中10种杀虫剂的最佳净化吸附剂组合为PSA 50 mg+无水硫酸镁150 mg+碳纳米管2 mg;番茄中7种杀虫剂不存在明显的基质效应,3种杀虫剂存在明显的基质抑制效应;10种杀虫剂在番茄中3个水平的添加回收率在65.75%~110.88%范围内,符合农药残留痕量分析试验要求。[结论]证明该分析方法适用于番茄中该10种杀虫剂的痕量残留分析,且具有灵敏度高,重复性好,价格低廉等优点。     

蔬菜中农残分析方法及残留农药去除率的研究

建立了一种气相色谱法检测蔬菜中农药残留的测定方法,考察了自制果蔬洗涤盐对蔬菜农药残留的去除率。采用基质固相分散法处理蔬菜样品,弗洛里硅土为固相吸附剂,丙酮/正己烷为洗脱液,各农药回收率在78%~107%,检出限0.003~0.006 mg/kg,定量限0.02~0.03 mg/kg,相对标准偏差小于8%。此方法简单、易操作,可用于评价各类洗涤剂去除农药的效果。为有效去除蔬菜表面残留的农药,以食盐为基本原料,通过复配表面活性剂制备出高效的果蔬洗涤盐,其对有机磷农药敌敌畏、乐果、毒死蜱的去除率在70%~94%,蔬菜中农药残留量均低于国家最高残留限量。     

高效液相色谱-串联质谱法测定蔬菜中多效唑等5种农药的分析方法

[目的]建立蔬菜中多效唑、吡虫啉、甲霜灵、灭多威、克百威5种农药的高效液相色谱-串联质谱联用的分析方法.[方法]样品经乙腈提取后,采用HPLC-MS/MS正离子模式下选择多反应监测(MRM)扫描测定.[结果]5种农药在0.01～0.5 mg/L范围内线性关系良好,相关系数为0.9958～0.9997.在0.05～0.5 mg/kg添加范围内,回收率在85.9％～103.8％之间,相对标准偏差为2.6％～12.1％.[结论]该方法简单、快速,结果准确,灵敏度、精密度和检测限都符合农药残留分析的要求.     

冬枣、金丝小枣中氯氰菊酯、氰戊菊酯、三唑酮残留量测定

采用气相色谱测定枣中氯氰菊酯、氰戊菊酯和三唑酮的残留量,农药残留运用单一溶剂(乙腈)提取,填有Florisil的层析柱净化,电子捕获–气相色谱法检测。本方法的回收率为78.5%～98.5%,检测限为0.005mg/kg～0.015mg/kg。本研究为枣中农药残留标准化测试方法的建立奠定了基础。     

Evaluation of GO nanosheets decorated by CuFe2O4 and CdS nanoparticles as photocatalyst for the degradation of dinoseb and imidacloprid pesticides

Pesticides are generally utilized one after another for crop conservation, and this pesticide utilization oftentimes resulting in combined pollution of their residues in the environment. An experimental study was performed on the degradation of dinoseb and imidacloprid. In this research, GO/CuFe₂O₄–CdS nanocomposite was synthesized as a high-efficiency photocatalyst for the process of pesticides pollutants from water. Field Emission Scanning Electron Microscopy with Energy Dispersive X-ray (FESEM-EDX), X-Ray Diffraction (XRD), Vibrating-sample Magnetometer (VSM), and Fourier Transform Infrared spectroscopy (FTIR) analyses are applied to study the properties of this nanocomposite. Dinoseb and imidacloprid as pesticide materials have been utilized as water contaminants and their degradation performance using the synthesized photocatalyst is considered. The effect of initial pH, photocatalyst amount, initial pesticide concentration and degradation time are investigated in this research. The optimum values for both pesticides were as follows: pollutant concentration was 10 ppm, the nanocatalyst amount was 100 mg, irradiation time was 100 min and the pH of pesticide solution equaled to 8. The results showed that the GO/CuFe₂O₄–CdS nanocomposite is the efficient nanocatalyst for degradation of these pesticides.     

Chemical process fault diagnosis based on a combined deep learning method

The study on fault detection and diagnosis (FDD) of chemical processes has always been the top priority of the chemical process safety. In this paper, a fault diagnosis method combining the deep convolutional with the recurrent neural network (DCRNN) is proposed. In this method, the data from chemical processes are input to the deep convolutional neural network (DCNN) to extract features in spatial domains, and then, the features are fused into the bidirectional recurrent neural network (BRNN). Due to the powerful capabilities of DCNN to extract features in spatial domains and the sensitivity to time series of RNN, the combined method can adaptively learn the dynamic information of the raw data in both spatial and temporal domains and has unique advantages in multivariate chemical processes. The application of the DCRNN model in the Tennessee Eastman (TE) process demonstrates the high accuracy of this proposal in identifying abnormal conditions for the chemical process, compared with the traditional fault identification algorithms of deep learning.     

核磁共振技术及其在农药残留分析中的应用

简述核磁共振技术(NMR)的发展史、基本原理.分别介绍了近年来NMR技术在含磷、含氟农药残留分析、农药杂质及其残留毒性、农药代谢物及其残留毒性、农药降解历程研究中的应用.展望了核磁共振技术在农药残留检测中的应用前景.     

Toxic chemical monitoring of agricultural bioproducts using nanomaterials-based sensors

Owing to the fast growth of the agricultural bioproducts industry, which requires its products to be fresh and visibly appealing, the increased use of imidacloprid pesticides has raised deep concerns about environmental effects, food quality, and the toxicity of residues. This has led to the development of various extraction methods of biochemicals and chemicals and their effective sensors for monitoring pesticide residues. We review the current commercial and nanotechnology-adopted techniques available in order to draw attention to the primary issues in the development of novel extraction and sensing systems using nanotechnology.     

有机磷农药在菠菜中残留测定方法研究

建立了同时测定菠菜中敌敌畏等6种有机磷农药残留的气相色谱法。结果表明,用丙酮、二氯甲烷提取菠菜中有机磷农药残留,在匀浆、抽滤1次,萃取2次时效果最好,提取的试样经DB-17毛细管柱分离,用配有火焰光度检测器的气相色谱仪能进行准确的定性和定量测定。方法检测下限达6.08×10-4 ~1.6610-3mg/kg,6种有机磷农药的回收率范围为82.52%~92.02%,相对标准偏差(RSD)为6.31%~17.06%。本方法符合国家农药残留量测定方法的要求。     

气相色谱法测定蔬菜中9种有机磷农药残留

建立毛细管柱气相色谱法测定蔬菜中9种有机磷农药残留的分析方法。蔬菜经均质,用乙腈提取,CARB/NH2柱净化,丙酮溶解定容,采用DB–1701毛细管柱和火焰光度检测器测定,一次进行9种有机磷农药残留检测。样品加标回收率在80.2%～102.2%之间,相对标准偏差在2.15%～5.32%之间,检出限在0.004 2～0.027 mg/kg之间。实验结果表明,该方法简便、快速、灵敏、准确,各项技术指标满足蔬菜中9种有机磷农药残留检测要求。     

手性农药残留分析的进展概况

手性农药在生物系统中的立体选择性已经引起人们的重视.只有在对映体形态水平上研究手性农药的环境问题才能弄清它们在环境中的行为和效应,才能就其对人类健康和生态系统的风险性作出准确的评价.本文就手性农药的残留测定方法进行了讨论,对其前处理技术和手性色谱分离方法作了较全面的综述.     

果蔬中常见有机磷和有机氯农药残留量分析

随着社会的发展和科技的进步,人们越来越关注自身的生活质量和食品健康。近几年农作物农药的过度使用问题引起了各界的关注,虽然有些剧毒农药被相关部门禁止使用,但是人们食用的果蔬中的农药残留量的多少成为了关注的焦点。本文使用电子俘获检测器和火焰光度检测器对几种常见的但是已经被禁用的几种农药进行有机氯和有机磷的气相色谱分析,以求得到抽测果蔬中相关的农药残留信息,以检测这几种被禁止使用的农药是否有违规使用的现象。     

蔬果中残留农药去除率的测定方法研究

建立一种洗涤剂对蔬果中农药残留去除率的检测方法。用浸泡法沾污蔬菜,经处理后,通过酶抑制率法,用分光光度计检测并计算出有机磷和氨基甲酸酯类农药沾污的青菜在处理前后的抑制率,从而得出其去除率。最后按GB／T14877—1994”食品中氨基甲酸酯类农药残留量的测定方法”用气相色谱对该洗涤剂进行了农药残留去除率的测定,与上述方法进行比较,两种方法无显著性差异。该方法无污染,比较简单,易于操作,可用于评价各类厨房用洗涤剂去除农药的效果。     

巢湖地区菠菜中有机磷农药残留状况调查

为调查巢湖地区菠菜中常用有机磷农药的残留情况,于2008年10月～2009年5月随机抽样检查巢湖产菠菜100份,采用气相色谱一质谱联用的检测分析方法,对菠菜中的7种常用有机磷农药残留进行测定。结果表明,有机磷农药的总检出率为25％,超标率为3％。     

我国农药残留检测技术现状

对我国近年来农药的生产、使用现状进行了回顾，对我国农药生产、使用中的结构问题进行了剖析，揭示了我国农残问题严重的根源，对我国的农药残留检测技术现状进行了归纳。较详细地论述了农残测定中样品的前处理技术，对各种提取、净化、浓缩和检测技术的优缺点进行了比较，并预测了超临界提取、固相萃取、固相微萃取、超临界流体色谱和多残留的系统解决方案等技术的采用是农残测定技术的发展方向，今后农残检测对象和检测目的物都将发生变化，提出了提高我国农残检测技术水平的措施。     

气质联用法测定生菜中多农药残留及其动态降解

采用气质联用仪，以生菜为基质，建立了蔬菜上常用及已被禁止使用的27种农药残留快速扫描方法。27种农药回收率在66．47％-130．08％之间，相对标准偏差在1．30％-25．68％之间，方法的最低检出限在0．0001—0．0594mg／kg之间。并应用所建立的方法研究了13种农药在生菜上喷施后的残留情况，为同时研究多种农药在同一作物上的代谢情况及各农药喷施后的安全间隔期提供依据。     

Degradation of atrazine using metalloporphyrins supported on TiO2 under visible light irradiation

A combined solar photo-Fenton and biological treatment is proposed for the decontamination of a mixture of five commercial pesticides commonly used in intensive agriculture Vydate (10% Oxamyl), Metomur (20% Methomyl), Couraze (20% Imidacloprid), Ditimur-40 (40% Dimethoate) and Scala (40% Pyrimethanil). Photo-Fenton experiments were conducted in a solar pilot reactor consisting of four compound parabolic collectors in which the pesticide mixture was treated at an original dissolved organic carbon (DOC) concentration of 200 mg/L in the presence of Fe²⁺ or Fe³⁺ concentration of 5, 20 and 55 mg/L. Ferrous ions were marginally more active than ferric in terms of active ingredient degradation, which followed zero order kinetics, more so in the early reaction stages. Photo-Fenton was also far more effective (by at least two orders of magnitude) than the respective dark reaction under identical experimental conditions.Irradiation for 50–100 min (normalized at 30 W/m² light intensity) at 20 mg/L Fe²⁺ was able to completely eliminate the active ingredients, and reduce DOC by about 15–50% and COD by 40–70%, respectively. At these conditions, ecotoxicity to the marine bacteria V. fischeri was substantially lessened, while aerobic biodegradability in tests with activated sludge was enhanced.