气相色谱法测定茶叶中八氯二丙醚(S-421)残留量

建立了一种测定茶叶中八氯二丙醚(S-421)残留量的气相色谱方法。试样中的八氯二丙醚(S-421)经丙酮提取、正己烷反萃取,然后用浓硫酸液-液分配磺化法,进行净化,以气相色谱法(GC-ECD)测定,外标法定量。试验结果表明:试样中加入0.005~0.05 mg.kg-1浓度水平的八氯二丙醚(S-421),回收率在85%~110%,检出限为0.005 mg.kg-1。同一样品10次测定的相对标准偏差小于10%。     

同时裂解甲基化气相色谱法鉴别合成胶粘剂

 应用同时裂解甲基化气相色谱法 (Py Me GC)对合成胶粘剂进行了鉴别。采用热丝型裂解器、氢火焰离子化气相色谱仪、FFAP毛细管柱、程序升温方式及季铵盐甲基化试剂 ,对刑事案件中常见的丙烯酸酯类及其改性体、醋酸乙烯酯、聚乙烯醇等合成胶粘剂进行了测定 ,并对样品裂解各主要组分峰进行了GC/MS定性分析 ,同时比较了相同样本用常规裂解气相色谱法 (Py GC)测定的结果。结果表明 :Py Me GC法比Py GC法可获得更多的物质组分信息 ,是一种适用于法庭科学鉴定的方法。     

气相色谱-离子色谱法测定矿物包裹体中气相和液相阴离子成分

用气相色谱法测定矿物包裹体(简称包体)中气相成分以及用化学法测定液相成分,已有报导,但用同一份试样测定包体中气液成分的方法,却报导甚少。1982年有人虽提出用同一份试样测定包体中气、液成分的方法,但试样用量(20—50克)大,分析方法无突破性进展。近年来,由于离子色谱仪的出现,使无机痕量阴离子,特别是难分离的F~-、Cl~-、Br~-、     

气相色谱法测定环境样品中的氰化物

氰化物是环境中常见的污染物,因其毒性大,是环境保护监测的重要项目之一。气相色谱法测定氰化物具有简便、灵敏、快速、干扰少、线性范围宽等优点。方法原理是在酸性溶液中,CN~-与Br_2生成CNBr,以还原剂除去多余的Br_2,经色谱柱分离后用ECD选择性地测定。     

Ag_2S电极测定水中低浓度氰化物

水中氰化物一般采用蒸馏分离比色法测定。但由于灵敏度较低(0.020毫克/升)而不能测定氰含量为ppb级的水样。为解决此问题,在Frant提出的Ag_2S电极间接测定法基础上,Clyster和Adams建议以PbS沉淀形式过滤除去硫化物,用硝酸银电位滴定测定氰化物。此法可测氰含量低达1ppb的试样(1微克/升),但存在大量碘化物和硫代硫酸盐时干扰测定。Durst亦曾用气体渗透膜渗析分离技术获得了较高灵敏度(0.5微克/升,但所用装置较复杂。综合上述方法优点并克服缺点,在0.1NNaOH介质条件下,我们以高锰酸钾氧化强还原性有机物及S~(2-),I-等。     

均相催化气相色谱法测定痕量氰离子

氰化物在工业生产和环境监测中是重要的分析项目之一。目前,检测氰化物的方法有多种,气相色谱法可将其转化为易挥发物后直接进行测定,本文利用氰离子在甲醇存     

水、土壤物料中氰根的测定

对水(饮用水、工业用水及工业排放水等)及土壤中微量氰化物的测定,目前多用双吡唑酮和吡啶-联苯胺比色法、以试银灵为指示剂的硝酸银容量法、离子选择电极法等。在这些方法中常用蒸馏-吸收法分离干扰元素,当试样中含铁氰化物或亚铁氰化物时会造成分析结果偏高。由于目前生产的氰离子电极尚不稳定,离子选择电极法灵敏度不高。采用EC-1型测氰仪具有操作简便、结果准确、灵敏度高等优点,水中所含的S~(2-)、Hg~+、Cu~(2+)、Fe~(2+)等干扰离子可用去干扰离子试剂去除。仪器测量范围为0—1.25微克氰。主要试剂氢化钾标准溶液:称取0.2560克分析纯氰化钾,用0.01M氢氧化钠溶液溶解并稀释于100毫升容量瓶中。此溶液1毫升约含1毫克氰离子,其准确浓度用硝酸银标准溶液标定;去干扰试剂:0.5     

气相色谱-甲基化-α-D-甘露糖苷内标法测定变异黄芪中的苦马豆素

建立以甲基化-α-D-甘露糖苷为内标物,用气相色谱测定变异黄芪中苦马豆素的方 法。植物样品经甲醇超声提取、氯仿去除杂质后,将碱性正丁醇萃取物用硅烷化试剂进行 衍生化,通过AT.SE-54毛细管柱分离,氢火焰离子化检测器检测,测得变异黄芪干草粉中 苦马豆素含量为115.7 mg/kg,加标回收率为82.6%~94.0%,相对标准偏差为2.8%。该方 法能用于疯草样品中苦马豆素的含量检测。     

水中痕量氰化物的比色测定

水中氰化物的测定是环境监测的重点项目之一。目前文献报道的检测氰化物的化学方法有多种,其中巴比妥酸钠一异烟酸钠法应用较广,但该法使用的氧化剂(氯胺T)水溶液不稳定,必须临用前配制,手     

柱前衍生化顶空-气相色谱-质谱法测定坚果和梅类食品中氰化物的含量北大核心CSCD

提出了柱前衍生化顶空-气相色谱-质谱法测定坚果和梅类食品中氰化物(以CN-计,下同)含量的方法。取样品2.0000 g,加1.0 g·L^(-1)氢氧化钠溶液约60 mL,混匀,超声提取20 min,冷却至室温后用1.0 g·L^(-1)氢氧化钠溶液定容至100 mL,过滤。取5 mL续滤液置于顶空瓶中,加入17%(体积分数)磷酸溶液200μL,混合后加入10 g·L^(-1)氯胺T溶液200μL,于55℃衍生30 min。以DB-624UI毛细管色谱柱为固定相,采用气相色谱-质谱法测定所得溶液中氰化物的含量。结果显示:CN-的质量浓度在200μg·L^(-1)以内与对应的氰化物衍生物的峰面积呈线性关系,检出限(3S/N)为0.01 mg·kg^(-1)。按照标准加入法进行回收试验,回收率为96.8%~103%,测定值的相对标准偏差(n=6)均小于4.0%。方法与国家标准方法GB 5009.36-2016中分光光度法进行对比,两种方法所得测定结果基本一致,无显著性差异。方法用于实际样品分析,结果显示坚果和梅类食品中都检出氰化物,建议将氰化物添加到GB 2762-2022的食品中污染物限量名录中,对其进行严格控制。     

Crystal structures of synthetic analgetics. V. Dextromoramide.

The molecular and crystal structure of dextromoramide has been determined by X-ray methods. The crystals are orthorhombic, space group P212121 with unit cell dimensions a = 9.720(4) A; b = 12.226(3) A; c = 18.381(3) A. The structure was determined by direct methods and the model refined to an R-value of 0.036 for 1788 observed reflections. The mean e.s.d.'s in bond lengths and angles are 0.004 A and 0.3, respectively. The morpholine moiety is nearly in antiposition relative to the quaternary carbon atom C6, the pertinent angle C6 - C7 - C9 - N2 being - 159.4. This conformation is similar to that previously reported for the bitartrate of the title compound. The pyrrolidine ring has the envelope conformation and the amide group is strictly planar. The conformation of some acyclic analgetics are discussed.     

Magnetic Recording of N.Q.R. spectra

This paper gives complete details of a unique system for Magnetically Recording the Analogue Spectral Signals from an N.Q.R. Spectrometer of the S.R.O./Marginal Oscillator type.This is a very low cost system, but producing a very high order of play-back resolution from recordings, using a normal domestic Cassette or Tape, Reel to Reel Recorder. Spectra can also be transmisted via telephone lines, fibre optic links or radio frequencies.This system has been used now for several years, and due to the design being based mainly om passive components, the order of reliability is extremely high, without any faults being encountered to dete!.     

13C-NMR. Spectroscopy of naturally occurring substances. XXXII. Vincaleucoblastine and related alkaloids.

The total assignment of the ¹³C-shifts of the complex Vinica rosea L. alkaloids vincaleucoblastine, leurosidine and leurosine and of a synthetic isomer of the latter is presented. The structure of leurosidine is corrected and a tentative structure for the acid-catalyzed product of isomerization of leurosine is proposed.     

Aromatic annelation. I. Synthesis of pyridines.

The preparation of substituted pyridines from cycloalkanones by elaboration of an aromatic ring is described.     

Metabolites of microorganisms. 130. Synthesis of delta-N-hydroxy-L-arginine

A synthesis of the antibiotically active amino acid, δ-N-hydroxy-L -arginine, starting from L -ornithine is described. In addition a new synthesis of δ-N-hydroxy-L -ornithine, an important building stone of many sideramines, is given.     

Aromatic Annelation. II. Synthesis of phenols.

The preparation of substituted phenols from cycloalkanones by elaboration of an aromatic ring is described.     

Prediction of retention indexes. III. Silylated derivatives of polar compounds.

Polar compounds containing hydroxyl, amino and carboxyl groups, singly or in combination, can be chromatographed after the polar functional groups are silylated. The silylated derivatives of acids, alcohols, amines, diols, amino alcohols, amino acids are shown to behave chromatographically as hydrocarbons, and their retention indexes can be readily predicted from their base values. The column difference, namely, the difference between the retention indexes of the analyte on polar and non-polar columns is minimal for the silylated derivatives in comparison to that observed for the underivatized analytes. This minimal column difference is attributed to the hydrocarbon-like chromatographic characteristics of the silylated derivatives. The retention indexes of the silyl derivatives appear to correlate with the atom number Z of the analyte.     

Crystal structures of synthetic analgetics. IV. Dextropropoxyphene.

The molecular and cystal structure of dextropropoxyphene has been determined by X-ray methods. The crystals are monoclinic, space group P21, with unit cell dimensions a=9.257(2) A; b=9.048(3) A; c=12.074(7) A; beta=93.01(4)degrees. The phase problem was solved by direct methods and the model refined to an R-value of 0.038 for 1799 observed reflections. E.s.d's are, in average, 0.004 A and O.3 degrees in interatomic distances and angles, respectively. The propylamine chain in nearly fully extended, the dihedral angel C4-C5-C7-N being -174.2 degrees. The conformation of this side chain is similar to that in the hydrochloride of the title compound. Thus the proposed bioactive conformation is not preferred by propoxyphene in the crystalline state, as was the case for the free base of methadone.     

An E.P.R. study of peptides after U.V. irradiation

Abstract— Various peptides of Gly, Ala, Phe, Tyr, and Trp have been irradiated with U.V. light in the solid state or in frozen aqueous solution. The radicals produced were studied by E.P.R. spectroscopy at low temperature and at room temperature. Radicals seem to occur preferentially on Gly or Ala when in the C-terminal position and there is evidence for a photosensitization of these amino acids by aromatic amino acids.     

Polyelectrolytic character of amylose. II.

Viscometric titrations of amylose are described. The curves confirm the earlier results of Rao and Foster. A more quantitative consideration is given concerning the changes of the electrostatic charge of the amylose molecules in the pH range of 11–12, where a minimum in the titration curve is found. A viscometric titration performed in solutions containing urea shows a considerably higher viscosity, especially at lower pH's; the curve, however, still shows a minimum between pH 11 and 12. Experiments on the dependence of [η] on the ionic strength at pH 12.7 also demonstrate the typical polyelectrolytic nature of amylose.