微波消解-石墨炉原子吸收光谱法和原子荧光光谱法测定蔬菜中痕量元素

用微波消解对蔬菜进行前处理，石墨炉原子吸收光谱法和原子荧光光谱法测定蔬菜中铅、镉、砷、汞的含量。用两种国家标准参考样品进行考察，结果表明该方法不仅简便、快捷而且分析结果可靠。并提出了该方法在蔬菜痕量元素测定中应注意的问题。     

Three-step extraction procedure for determination of heavy metals availability to vegetables

A three-step sequential extraction procedure was used to determine the concentration of heavy metal speciation forms in soil. The procedure allows one to identify the pool of heavy metals that can be potentially mobilised under changes in soil pH value or redox potential. It has been shown that similar portions of heavy metals are present in reducible, oxidisable and residual fractions. It was found that soil chemical properties significantly affected the distribution of heavy metals among different fractions and their uptake by vegetables. Cadmium was a dominant element which occurred in the exchangeable fraction—the most bioavailable and potentially toxic.     

蔬菜中残留农药的石墨化碳黑净化和气相色谱-质谱检测方法

研究石墨化碳黑对不同类型农药的吸附规律和对色素的吸附能力,比较了不同洗脱溶剂对色素的洗脱能力和对待测物在GCB上洗脱顺序的影响。同时测试了GCB和活性炭的吸附-解吸附等温线,表明不同的表面结构造成了两种吸附剂不同的吸附机理及对色素吸附能力的显著差别。结果表明,GCB对含有芳香环、结构具有一定对称性的农药吸附力最强,而对叶绿素吸附强于叶黄素和番茄红素。最后根据实验结果针对性地建立了残留在蔬菜中农药多残留方法:样品经GCB净化,以丙酮/乙酸乙酯(1∶1,V/V)为洗脱液,最后用气相色谱-质谱选择离子存储(GC-MS/SIS)检测,所有农药的检出限保持在0.002~0.10 mg/kg范围内。     

表面活性剂对检测蔬菜中残留农药的植物酯酶方法的作用

在所测试的5种表面活性剂(OP、CTMAB、CPC、SLS及SDS)中,阴离子表面活性剂、十二烷基硫酸钠(SDS),对被植物酯酶催化的显色反应呈现显著的增加灵敏度和稳定性的作用.而此显色反应因有机磷农药的存在而受到抑制,显色反应灵敏度的增加幅度达70%左右,对影响显色反应的各种因素作了较深入的试验并对其反应条件作了优化.所提出的方法已应用于小青菜中残留敌敌畏农药的测定,并在此样品的基础上对方法的精密度及回收率作了试验,测得其相对标准偏差(n=6)为0.87%,平均回收率为111%.     

Time-resolved characterization of laser-induced plasma from fresh potatoes

Optical emission of laser-induced plasma on the surface of fresh vegetables provides sensitive analysis of trace elements for in situ or online detection of these materials. This emergent technique promises applications with expected outcomes in food security or nutrition quality, as well as environment pollution detection. Characterization of the plasma induced on such soft and humid materials represents the first step towards quantitative measurement using this technique. In this paper, we present the experimental setup and protocol that optimize the plasma generation on fresh vegetables, potatoes for instance. The temporal evolution of the plasma properties are investigated using time-resolved laser-induced breakdown spectroscopy (LIBS). In particular, the electron density and the temperatures of the plasma are reported as functions of its decay time. The temperatures are evaluated from the well known Boltzmann and Saha-Boltzmann plot methods. These temperatures are further compared to that of the typical molecular species, CN, for laser-induced plasma from plant materials. This comparison validates the local thermodynamic equilibrium (LTE) in the specific case of fresh vegetables ablated in the typical LIBS conditions. A study of the temporal evolution of the signal to noise ratio also provides practical indications for an optimized detection of trace elements. We demonstrate finally that, under certain conditions, the calibration-free LIBS procedure can be applied to determine the concentrations of trace elements in fresh vegetables.     

Highly sensitive and selective organophosphate screening in twelve commodities of fruits,vegetables and herbal medicines by dispersive liquid–liquid microextraction

The article describes a simple sample pretreatment procedure for the analysis of ten organophosphorus pesticides using dispersive liquid–liquid microextraction (DLLME) followed by gas chromatography–mass spectrometry (GC–MS) in three distinctively different types of matrices: fresh fruits, fresh vegetables and dried herbs. The method was carefully developed, focusing on the chemistry of various dispersive solvents, to achieve simultaneous, comprehensive extraction and preconcentration in a great span of selected matrices. According to matrix-matched validation study, the set of optimized DLLME conditions has been proven robust to determine target OPPs within a wide linear range from 0.1 to 1000 μg L⁻¹. With limited usage of organic extractants, remarkable enrichment factors up to 100-fold were obtained, enabling ultra-trace pesticide quantification down to sub-ppt levels at 0.12–4.92 ng kg⁻¹. Practical application of the method was illustrated by quantitative recovery (70–119%) and good precision (2.6–10% R.S.D.) in a representative range of three fruits and four vegetable commodities featured by the CODEX Alimentarius classification as well as their unique matrix compositions. A careful selection of dried herbs was further classified based on their morphological structures to validate analytical ruggedness of the method. Compared with existing methods for food analysis vis-à-vis OPPs, the present method is superior in terms of high sample throughput, minimal solvent consumption, and small sample size requirement. An additional, significant aspect of this universal DLLME method is that it models sample pretreatment methods with wide coverage of analytical matrices that are more effective, more comprehensive, and more flexible than those currently being used.     

Determination of Heavy Metal Content in Vegetables and Oils From Spain and Morocco by Inductively Coupled Plasma Mass Spectrometry

An optimized inductively coupled plasma mass spectrometry method was used to analyze trace metals (As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, and Sn) in vegetable and oil samples. Prior to analysis, the samples were accurately weighed into a Teflon digestion vessel and the metals extracted from their matrix by using nitric acid and hydrogen peroxide in a closed-vessel digestion system. The proposed method is sensitive, with limits of detection between 5 and 38 ng/kg, and precise, with relative standard deviations from 2.8 to 6.1%. In order to verify its accuracy, the method was used to analyze the Standard Reference Materials NCS ZC85006 Tomato and Certified Used Oil HU-1. The method was successfully applied to the comparative determination of residues of the studied metals in vegetable (tomato, pepper, onion, spinach, lettuce, carrots, and marrow squash) and oil samples (virgin olive, maize, sunflower, and olive pomace) from Spain and Morocco. The results obtained revealed that the contents in metal residues depend on the particular type of food and its origin, probably due to the different production, processing, storage, and preservation methods.     

Determination of Trifloxystrobin,Tebufenozide, and Halofenozide in Foods by Micellar Electrokinetic Capillary Chromatography

A simple and rapid micellar electrokinetic capillary chromatography method of trifloxystrobin, tebufenozide, and halofenozide has been developed. The separation was performed in a 10 mM borate-18 mM SDS buffer solution (pH = 9.0), containing 22.5% v/v of acetonitrile, 25 kV and detection at 202 nm. The linear concentration range of application was 0.5–10.0 mg L^?1, with a detection limit of 0.094 mg kg^?1 for trifloxystrobin and 0.088 mg kg^?1 for tebufenozide and halofenozide. Analysis yielded good reproducibility (RSD between 1.7–8.7%). The applicability of the method was tested by analyzing several fortified samples of tomato, celery, and apple juices. Recovery levels were between 70.0 and 110.8%.     

蔬菜中矿质元素的测定与研究

采用ICP-AES法同时测定8种蔬菜中的7种微量元素Sr、Ba、Fe、Cu、Zn、Mn、Mo，回收率在91．9％-108．4％之间。     

A new multi-residue method for analysis of pesticide residues in fruit and vegetables using liquid chromatography with tandem mass spectrometric detection

A new multi-residue method for determination of pesticide residues in a wide variety of fruit and vegetables, using the National Food Administration (NFA) ethyl acetate extraction and determination by means of LC-MS/MS, is presented. The method includes pesticides normally detected by LC-UV or LC-fluorescence such as benzimidazoles, carbamates, N-methylcarbamates and organophosphorus compounds with an oxidisable sulphide group as well. After extraction with ethyl acetate, the extract is concentrated and an aliquot of the extract is evaporated to dryness and redissolved in methanol before injection on LC-MS/MS. The method has been validated for 57 different pesticides and metabolites. Representative species from different commodity groups were chosen as matrices in order to study the influence from different matrices on recoveries. The fortification levels studied were 0.01-0.5 mg kg(-1). Matrix effects were tested for all matrices by means of standard addition to blank extracts. The matrix effect, expressed as signal in solvent compared to signal in matrix, was in general found to be small. The obtained recoveries are, with a few exceptions, in the range 70-100%. The proposed method is quick and straightforward and no additional clean-up steps are needed. The method can be used for the analysis of all 57 pesticides in one single determination step at 0.01 mg kg(-1).