植物酯酶应用于有机磷农药残留分析技术的研究进展

有机磷农药残留在食品中,进入人体危害人类健康.因此,快速而灵敏的检测技术是预防农药残留危害的前提条件.而酶抑制技术正是一项快速检验技术.本文作者介绍了农药残留分析的现状,详细分析了植物酯酶应用于农药残留分析技术的研究进展.     

参考JJF-1059对农药多残留分析国标方法NY/T761.1-2004的不确定度评价研究

参考JJF-1059<测量不确定度评定与表示>,对农药多残留分析国标方法NY/1761.1-2004(蔬菜和水果中有机磷、有机氯、拟除虫菊酯和氨基甲酸酯类农药多残留检测方法)进行了不确定度的评价研究.对黄瓜基质上的5种有机磷农药(敌敌畏,乐果,甲基对硫磷,毒死蜱,克线磷),应用国标NY/T761方法进行检测.从标准过程、质量称量过程、体积定容和样品处理过程等方面分析农药残留操作环节的不确定度.结果表明,不同农药或浓度水平之间扩展不确定度并没有显著差异,校准过程占整个不确定度的比重随着待测物浓度水平降低而显著提高.     

蔬菜、水果中多农药残留的筛查

近年来,食品安全问题引起了人们的高度重视,农药残留污染是制约食品安全的重要因素.在食品农药残留检测方法中,农药残留检测的种类越来越多,农药残留的限量标淮越来越严,人们对食品中农药残留的检测正在不断地探索快速准确的有效方法[1].解卷积报告软件(DRS)是由安捷伦公司研发,其目的主要用于农药和可疑内分泌干扰物的筛查.该软件由安捷伦质谱工作站、自动质谱解卷积和鉴定系统(AMDIS)以及NIST检索三部分组成.AMDIS需要使用包含有保留时间的自动质谱解卷积和鉴定系统.DRS能大大提高复杂基质中痕量化合物的定性能力,并且在SCAN和SIM两种模式下均可采用DRS进行数据处理.保留时间锁定(RTL)和RTL数据库是DRS的一个组成部分,它无需使用标样,只需采用数据库中建立的GC/MS条件,即可实现对农药和一些内分泌干扰物分析鉴定.     

8种农药的大口径毛细管气相色谱分析

1　引　　言2 0世纪 80年代 ,毛细管气相色谱 (CGC)技术就广泛用于农药残留分析。现在毛细管气相色谱与固相萃取、固相微萃取、质谱等技术一起 ,被广泛地应用于农药的多残留分析。但作为农药原药和制剂的有效成分的常规分析 ,直至进入2 0世纪 90年代后才在农药国际标准分析方法 (CIPAC)手册中相继出现。近年来 ,随着大口径毛细管推广应用和一些重大技术的改进 ,毛细管气相色谱作为农药的常规分析方法 ,发展比较快。到目前为止 ,CIPAC已经建立了近 2 0个农药原药及其制剂的毛细管气相色谱标准分析方法。大口径毛细管气相色谱法具有分析…     

流动分析-红外光谱联用技术在农药和食品分析中的应用

综述了流动分析-红外光谱联用技术在农药残留、农药制剂质量控制、食品检测(包括乙醇、糖类、有机酸和咖啡因)等领域的应用,并对该技术的应用前景进行了展望(引用文献52篇)。     

基质固相分散净化-气相色谱法测定竹笋中7种农药多残留

通过基质固相分散净化,气相色谱-电子捕获检测器(GC-μ-ECD)检测,建立了竹笋中7种农药多残留测定方法,实现了对竹笋中六六六、滴滴涕、五氯硝基苯、甲氰菊酯、氯氰菊酯、三氟氯氰菊酯和毒死蜱农药多残留的同时测定。在0.05～0.2 mg/kg添加水平下,7种农药的回收率在82.2%～123.5%之间,相对标准偏差(RSD)均小于6.1%。该方法适用于竹笋中农药多残留的检测。     

微波辅助萃取法测定烟草中有机氯类农药残留量

建立了一种微波辅助萃取-固相萃取净化测定烟草中17种有机氯类农药残留量的新方法. 样品用V(正己烷):V(乙酸乙酯)＝1:1提取, 提取液经Florisil固相萃取柱净化后, 采用气相色谱-电子捕获检测器(GC-μECD)进行检测. 17种有机氯农药的0.01、 0.05 mg/kg和0.5 mg/kg加标回收率均在82%以上, RSD在0.11%～8.2%之间, 能满足当前烟草中有机氯农药残留的检测要求.     

QuEchERS方法专用于分散SPE产品的农药残留分析

全球每年大约有超过2000种食品样品要进行农药残留分析,分析的质量必须符合特定的要求,且力求快速、简便、易操作、低成本、溶剂使用少、低污染等。近40年来,虽然大量的分析方法不断涌现及更新,然而这些方法很难同时对绝大多数农药达到较高质量的分析。2003年,QuEchERS(Quick,Easy,Cheap,Effective,Rugged and Safe)方法在美国诞生,以一种快速、简便、价格低廉的分析方法实现高质量的农药残留分析。不同于传统的SPE小柱净化方法,在此方法中,使用分散SPE净化是非常方便的。通过将水溶性提取液(如乙腈)与分散的SPE填料(如Supelclean PSA,Envi-carb和Discovery DSC-18)、高含量的盐(如氯化钠和硫酸镁)和缓冲试剂(如柠檬酸盐)相混合,然后经振动和离心,得到的上清液就可直接用于色谱分析。(志)QuEchERS方法专用于分散SPE产品的农药残留分析@志     

凝胶色谱净化-毛细管气相色谱法同时测定蔬菜中23种农药残留

采用乙酸乙酯匀浆提取残留在蔬菜中的农药,过凝胶渗透色谱净化柱,用环己烷-乙酸乙酯(体积比1:1)淋洗液以5 mL·min-1的流量洗脱凝胶柱,经淋洗收集并浓缩第85～175 mL流分,用氮磷检测器对蔬菜中23种农药残留同时进行检测.采用三阶程序升温,23种杀虫剂在HP-5毛细管柱上得到较好分离,回收率在75.6%～110.7%之间,相对标准偏差在0.56%～8.26%之间,方法检出限为0.002～0.005 mg·kg-1,在0.5～5.0 mg·L-1范围内呈线性.方法适用于蔬菜、水果等植物性食品中农药残留的分析.     

桃中农药残留分析及膳食暴露评估研究

为明确并量化食用桃途径的农药膳食摄入风险水平,通过对19个桃主产区采集的98份样品进行农药残留检测,对桃中的农药残留急/慢性膳食摄入风险进行评估,并借鉴英国兽药残留委员会兽药残留风险排序矩阵进行农药和样品风险排序。结果在桃中检出了38种农药残留,98个样品的检出率为95.9%,检出的农药含量为0.007 4～3.399 3 mg/kg;检出农药的慢性膳食摄入风险(%ADI)和急性膳食摄入风险(%ARfD)的平均值分别为0.89%和11.09%,风险均低于100%,不会对人体产生慢性或急性风险;风险排序结果表明桃果品中氟虫腈、硫丹、灭多威、丁硫克百威、毒死蜱、联苯菊酯为6种为高风险农药,应在生产和质量安全监管中予以重点关注。该文为桃安全消费、农药残留监管和农药最大残留限量(MRLs)制修订提供了科学依据。     

Solvent extraction separation of In/III/-Tl/III/ and Hg/II/-Cd/II/-Co/II/ with sulphoxides

Solvent extraction studies have been made on some metals: In/III/-Tl/III/ and Hg/II/-Cd/II/-Co/II/, from ammonium thiocyanate solutions by dialkyl sulphoxides. Separation of these metals from one another can be achieved by suitable choice of the extracted conditions. The nature of the extractable metal species has been elucidated.     

Synthesis of chlorobis/β-diketonato/oxotechnetium/V/ and tris/β-diketonato/technetium/III/ complexes

Chlorobis/-diketonato/ oxotechnetium/V/ complexes [TcOCl/-dik/₂, -diketone=acetylacetone, benzoylacetone and dibenzoylmethane] were newly synthesized using macroamount of⁹⁹Tc. These complexes were further separated into geometrical isomers. Furthermore, an improvement of the yields for the syntheses of tris/-dike-tonato/technetium/III/ complexes [Tc/-dik/₃, -diketone=acetylacetone, benzoylacetone and 2-thenoyltrifluoroacetone] was examined using Tc/III/-thiourea complexes as a starting material.     

Crystal structure of Na3PO4 · 12H2O

The crystal structure of trisodium monophosphate hemihydrate was determined. The space group is $\text{C2}\text{c}$ and a unit cell contains eight formula units. The unit cell dimensions of $\text{Na}{}_3\text{PO}{}_4\text{·}\text{1}\text{2}\text{H}{}_2\text{O}$ are a = 9.631(3), b = 5.416(2), c = 16.938(8) Å, β = 102.60(5)°. The final R value is 0.027 for a set of 1430 independent reflections. This atomic arrangement is mainly a three-dimensional network of distorted NaO₆ octahedra. The hydrogen bonding scheme is given.     

Simultaneous propane dehydrogenation andco2hydrogenation overCrOx/SiO2catalyst

Summary Single reverse water-gas shift (RWGS) and dehydrogenation of propane with CO₂(DH-CO₂) reactions in the presence and absence of the CrO_x/SiO₂ catalyst have been studied between 673 and 873 K. It was found that the CrO_x/SiO₂ catalyst is active both in the dehydrogenation of propane and in the RWGS reactions. The obtained results suggest that the dehydrogenation of propane to propene in the presence of CO₂on CrO_x/SiO₂can be facilitated by the RWGS reaction.</o:p>     

An investigation of the promotional effect of propylene or propane traces on the activity of sulfatedPt/g-Al2O3andPt-Sn/g-Al2O3inCH4combustion

Summary A strong promoting effect of the presence of C₃H₈or C₃H₆was determined for the combustion of CH₄in excess oxygen, over pre-sulfated 1%Pt/g-Al₂O₃and pre-sulfated 1%Pt-2%Sn/g-Al₂O₃catalysts.</o:p>     

Direct synthesis of dimethyl carbonate ?from CH3OH AND CO2 by H3PW12O40/CexTi1-xO2 catalyst

Summary Ce_xTi_1-xO₂ and H₃PW₁₂O₄₀/Ce_xTi_1-xO₂ catalysts were prepared using a sol-gel method, and applied to the direct synthesis of dimethyl carbonate from methanol and carbon dioxide. H₃PW₁₂O₄₀/Ce_xTi_1-xO₂ showed a better catalytic performance than the corresponding Ce_xTi_1-xO₂, due to the bifunctional catalysis of Br?nsted acid sites (provided by H₃PW₁₂O₄₀) and base sites (provided by Ce_xTi_1-xO₂). H₃PW₁₂O₄₀/Ce_0.1Ti_0.9O₂ showed the highest catalytic performance among the H₃PW₁₂O₄₀/Ce_xTi_1-xO₂ catalysts.     

Oxygen defect K2NiF4-type oxides: The compounds La2−xSrxCuO4−x2+δ

Oxygen defect K₂NiF₄-type oxides $\text{La}{}_{\mathrm{2?x}}\text{Sr}{}_{\mathrm{x}}\text{CuO}{}_{\mathrm{<mtext>4?</mtext><mtext>x</mtext><mtext>2</mtext><mtext>+\delta </mtext>}}$ have been synthesized for a wide composition range: 0 ≤ x ≤ 1.34. From the X-ray and electron diffraction study three domains have been characterized: orthorhombic compounds with La₂CuO₄ structure for 0 ≤ x < 0.10, tetragonal oxides similar to LaSrCuO₄ for 0.10 ≤ x < 1 and several superstructures derived from the tetragonal cell ( with n = 3, 4, 4.5, 5, 6) for 1 ≤ x ≤ 1.34. The compounds corresponding to 0 < x < 1 differ from the other oxides in that they are characterized by the presence of copper with two oxidation states: + 2 and + 3. A model structure for La_0.8Sr_1.2CuλO_3.4, in which copper has only the + 2 oxidation state, and for which the actual cell is tegragonal—a = 18.80₄ Å and c = 12.94 Å—has been established. The particular structural evolution of these compounds is discussed in terms of a competition between the capability of Cu(II) to be oxidized to Cu(III) and the ordering of oxygen vacancies.     

A study of the spinel materials LiTi2O4 and Li43Ti53O4 by photoelectron spectroscopy

HeI-excited valence-band ultraviolet photoelectron spectra and MgKα-excited Ti-2p X-ray photoelectron spectra are reported for the spinel materials LiTi₂O₄ and $\text{Li}{}_{\mathrm{<mtext>4</mtext><mtext>3</mtext>}}\text{Ti}{}_{\mathrm{<mtext>5</mtext><mtext>3</mtext>}}\text{O}{}_4$. The presence of a Fermi edge in the ultraviolet photoelectron spectrum of LiTi₂O₄ confirms the metallic nature of this material, although the measured density of states at the Fermi energy is much lower than that expected from an independent-electron interpretation of the magnetic susceptibility. This difference is attributed to a strong interaction of the conduction electrons with the lattice vibrations. The localization of conduction electrons that occurs in the final state in the Ti-2p X-ray photoelectron spectrum of LiTi₂O₄ is attributed to a Coulomb interaction with a core hole.     

LixNi0.8-yCo0.2ZnyOp的合成及电化学性能研究

A series of single-phase Li_xNi_0.8-yCo_0.2Zn_yO_p(0.96 ≤x≤ 1.10， 0 ≤y≤ 0.05， 2 ≤p≤ 2(1+y) ) (different in the y values) were synthesized by a two-step solid state reaction method， in which LiOH·H₂O， Zn-doped spherical Ni(OH)₂ and Co₂O₃ were used as the precursors. The ICP-AES analyses proved that the Zn-doped compounds synthesized had the nonstoichiometric form. The results of the XRD， SEM identified that the uniform particles of the as-prepared materials having a good layered structure were fine， narrowly distributed and well crystallized. The electrochemical performance test was carried out and the results showed that the as-prepared Zn-doped materials had not only a high capacity， but also a better cycling stability characterization than the un-doped one. The Li_1.06Ni_0.75Co_0.22Zn_0.03O_2.03 material has an initial reversible capacity as high as 160.5mAh·g^-1; and a first discharge efficiency 89.2%， and exhibits satisfactory cyclic stability with 90% retainable capacity after 50 cycles.     

Visible light-sensitive yellow TiO2−xNx and Fe-N co-doped Ti1−yFeyO2−xNx anatase photocatalysts

Nitrogen substituted yellow colored anatase TiO_2−xN_x and Fe-N co-doped Ti_1−yFe_yO_2−xN_x have been easily synthesized by novel hydrazine method. White anatase TiO_2−δ and N/Fe-N-doped samples are semiconducting and the presence of ESR signals at g ∼1.994-2.0025 supports the oxygen vacancy and g∼4.3 indicates Fe³⁺ in the lattice. TiO_2−xN_x has higher conductivity than TiO_2−x and Fe/Fe-N-doped anatase and the UV absorption edge of white TiO_2−x extends in the visible region in N, Fe and Fe-N co-doped TiO₂, which show, respectively, two band gaps at ∼3.25/2.63, ∼3.31/2.44 and 2.8/2.44 eV. An activation energy of ∼1.8 eV is observed in Arrhenius log resistivity vs. 1/T plots for all samples. All TiO₂ and Fe-doped TiO₂ show low 2-propanol photodegradation activity but have significant NO photodestruction capability, both in UV and visible regions, while standard Degussa P-25 is incapable in destroying NO in the visible region The mid-gap levels that these N and Fe-N-doped TiO₂ consist may cause this discrepancy in their photocatalytic activities.