Retention behavior of arsenobetaine, arsenocholine, trimethylarsine oxide and tetramethylarsonium iodide on a styrene-divinylbenzene column with benzenesulfonates as ion-pairing reagents

The pH-dependent retention behavior of arsenobetaine, arsenocholine, trimethylarsine oxide, tetramethylarsonium iodide (cationic arsenic compounds), arsenite, arsenate, methylarsonic acid, and dimethylarsinic acid (anionic arsenic compounds) was studied on a Hamilton PRP-1 reversed-phase column (250×4.1 mm I.D.) with 10 mM aqueous solutions of benzensulfonic acids (X-C₆H₄SO₃⁻; X=H, 4-HO, 3-CO₂H; 4-HO-3-HO₂C-C₆H₃SO₃⁻) as ion-pairing reagents in the pH range 2–5 using flame atomic absorption spectrometry as the arsenic-specific detector. The dependencies of the k′-values of the ‘cationic’ arsenic compounds was rationalized on the basis of the protonation/deprotonation behavior of the arsenic compounds and of the four benzenesulfonates. The results provided evidence for the formation of a cationic species from trimethylarsine oxide below pH 3. Benzenesulfonate is the most hydrophobic ion-pairing reagent causing strong retention of the cationic arsenic compounds and consequently impeding their rapid separation. With the less hydrophobic, substituted benzenesulfonates the cationic arsenic compounds had retention times not exceeding 6 min. At a flow-rate of 1.5 cm³ min⁻¹ 10 mM aqueous 3-carboxy-4-hydroxybenzenesulfonate solution adjusted to pH 3.5 allowed the separation of arsenate, methylarsonic acid, arsenobetaine, trimethylarsine oxide, the tetramethylarsonium ion, and arsenocholine within 3 min. Dimethylarsinic acid coelutes with arsenobetaine at pH 3.5, but can be separated from arsenobetaine with the same mobile phase at pH 2.5. At pH 2.5 the signals for trimethylarsine oxide, the tetramethylarsonium ion, and arsenocholine are too broad to be useful for quantification. Arsenite and methylarsonic acid cannot be separated under these conditions.     

Plasma chromatography of n-alkyl acetates

Plasma chromatography is a technique which permits characterization and analysis of trace constituents in a gaseous mixture at atmospheric pressure. It is especially well suited as a gas chromatographic detector. Operating at atmospheric pressure, the instrument uses either air or nitrogen carrier gas into which the sample is injected directly or through a gas chromatograph. The compounds are identified by their characteristic positive and negative mobility spectra, which consist of simple molecular and dissociative ions. Quantities as low as 10⁻⁶ to 10⁻¹² g are detectable. For use as a gas chromatographic detector, reference mobility spectra of compounds are needed. Those of n-alkanes, alcohols, ketones, halogenated aromatics, substituted nitrobenzenes, polychlorinated biphenyls, alkyl halides, aliphatic N-nitrosamines and isomeric phthalic acids have been previously reported. This study reports the reference mobility spectra produced by n-alkyl acetates. These compounds display strong positive mobility spectra but no negative mobility spectra. The spectra all show characteristic MH⁺, M(H₂O)_nH⁺ and (M₂)H⁺ along with the alkyl fragment ions.     

电子制冷预浓缩-双柱气相色谱-质谱/氢火焰检测器法测定空气中104种挥发性有机物

基于吸附剂辅助电子制冷预浓缩技术，建立了多维切割双柱气相色谱-质谱/氢火焰离子化检测器（GC-MS/FID）同时测定环境空气中104种挥发性有机物（VOCs）的方法。将采集于苏玛罐中的环境空气样品在配有吸附剂的电子制冷预浓缩系统中富集、脱附、除水、除CO₂和浓缩，然后通过GC-MS/FID的多维切割单元将C₂~C₃组分和C₄~C₁₂组分分别引入PLOT柱和InterCap-624柱进行分离。C₂~C₃组分用FID检测，以保留时间定性、外标法定量；C₄~C₁₂组分采用电子轰击离子源质谱检测，以保留时间和特征离子定性、内标法定量。考察了冷阱吸附剂种类、辅助压力控制单元压力设置、双柱切换时间切割点等参数对分析结果的影响，优化了GC-MS/FID条件，并评估了在此优化条件下的方法性能。104种VOCs在0.0446~0.892 μmol/m³范围内线性关系良好，相关系数（r）为0.9984~0.9999，对0.0446 μmol/m³和0.223 μmol/m³水平的混合标准气体重复6次进样，平均回收率为86.4%~116.1%，相对标准偏差为0.9%~11.3%；方法的检出限为0.145~1.90 μg/m³，定量限为0.435~5.70 μg/m³。该法稳定性好，灵敏度高，操作简便，可用于环境空气中104种VOCs的测定。     

Surface ionization detector with a supersonic free jet for gas chromatography some applications

A new design for a gas chromatographic surface ionization detector based upon hyperthermal positive surface ionization has been developed: There were two requirements: supersonic free jet nozzle and the high work function surface of Re-oxide. This detector, which is highly sensitive in response to all organic compounds, can be operated as an universal detector with an additional selectivity towards some species that have low ionization energy, but with selectivity to a much lesser degree than a conventional surface ionization detector. The minimum detectable amount of toluene is ca. 10⁻¹² g/s with a linearity greater than 10⁴. Some applications are demonstrated using three examples for the analysis of different formulations: (1), terpene mixture, (2), polycyclic aromatic hydrocarbon mixture and (3), alkyl alcohol mixture.     

Synthesis and resonance raman study of conductive iodinated materials derived from [M(dmit)(phen)] complexes [M = Pd(II), Pt(II)]

The synthesis and characterization of the [M(dmit)(phen)] complexes [M = Pd(II), Pt(II); H₂dmit = 4,5-dimercapto-1,3-dithiole-2-thione; PHEN = 1,10-phenanthroline) and of the iodinated [M(dmit)(phen)]I compounds are described. The conductivity of [M(admit)(phen)] increases upon oxidation by a factor of 10⁶, and is ca. 5 × 10⁻³ ohm⁻ cm⁻ for the [M(admit)(phen)]I compounds. The nature of the iodine species in these solids is determined by UV-visible and resonance Raman spectroscopies. The only polyiodide present is I⁻₃ and, thus, the charge distribution can be expressed as [M(dmit) (phen)^0.33+[I⁻₃]_0.33.     

Amberlite XAD-2 functionalized with o-aminophenol: synthesis and applications as extractant for copper(II), cobalt(II), cadmium(II), nickel(II), zinc(II) and lead(II)

A stable chelating resin matrix was synthesized by covalently linking o-aminophenol (o-AP) with the benzene ring of the polystyrene–divinylbenzene resin, Amberlite XAD-2, through a –N=N– group. Elemental analyses, thermogravimetric analysis (TGA) and infrared spectra have characterized the resulting chelating resin. It has been used to preconcentrate Cu²⁺, Cd²⁺, Co²⁺, Ni²⁺, Zn²⁺ and Pb²⁺, prior to their determination by flame atomic absorption spectrometry. The optimum pH values for quantitative sorption of Cu, Cd, Co, Ni, Zn and Pb are 6.2–7.4, 5.6–7.2, 5.6–9.0, 6.0–9.0, 5.7–7.0 and 5.0–6.0, respectively. These metals are desorbed (recovery 91–98%) with 4 mol dm⁻³ HNO₃. The sorption capacity of the resin is 3.37, 3.42, 3.29, 3.24, 2.94 and 3.32 mg of metal g⁻¹ of resin, respectively, for Cu, Cd, Co, Ni, Zn and Pb. The effect of NaF, NaCl, NaNO₃, Na₂SO₄, and Na₃PO₄ on the sorption of these metal ions has been investigated. These electrolytes are tolerable up to 0.01 mol dm⁻³ in case of all the metal ions, except Cl⁻ which is tolerable even up to 0.1 mol dm⁻³ for Zn and 1.0 mol dm⁻³ for Pb. The preconcentration factor for Cu, Cd, Co, Ni, Zn and Pb are 50, 50, 100, 65, 40 and 40 (concentration level 10–25 μg dm⁻³) respectively. Simultaneous enrichment of the six metals is possible. The method has been applied to determine Cu, Cd, Co, Ni, Zn and Pb content in well water samples (RSD≤8%).     

Circularly polarized luminescence induced by excimer based on pyrene-modified binaphthol

A new chiral bromobinaphthol-pyrene compound was developed to achieve a green circularly polarized luminescence (CPL) from its excimer with a dissymmetry factor (|g_lum|) value of 4.3×10^-3 and a high quantum yield Φ_{F, solid} up to 55.9%, while no CPL signals could be observed for the blue luminescence from unimolecule. Meanwhile, reversal CPL signals can be observed from both concentrated solution and solid.     

硼化合物的研究(Ⅳ)——硼烷阴离子铵盐的合成与性质

通过硼烷阴离子网-B₃H₈^-和闭-B₁₀H₁₀^2-与一系列卤化铵反应合成出十五种新的硼烷阴离子铵盐。这些新化合物均经元素分析和红外光谱鉴定。它们的差热分析结果表明:B₁₀H₁₀^2-铵盐的热稳定性高于B₃H₈^-铵盐;在季铵离子中导入氨基以后,化合物的热稳定性降低,并且导入的氨基愈多,化合物愈不稳定。     

GC-MS/FID测定环境空气中57种臭氧前体物

建立了GC-MS/FID测定环境空气中57种臭氧前体物的分析方法.优化三级冷阱捕集温度、三级冷阱解析温度、初始柱温、毛细管色谱柱等实验条件.优化条件为:采用硅烷化的苏玛罐采集环境空气,目标组分经三级冷阱在-180℃低温浓缩富集,80℃解析,初始柱温为15℃,结合中心切割技术,将乙烷、乙烯、乙炔、丙烷、丙烯切割至TG-B...     

Fe~(3+)辅助煤浆氧化制氢研究

利用Fe~(3+)/Fe~(2+)电对的相互转化原理,在水热反应釜中用Fe~(3+)氧化煤浆得到Fe~(2+),将Fe~(2+)在电解槽中电解氧化,在阴极产生氢气,从而通过两步反应形成一个新的煤浆电氧化制氢工艺。进行了九次水热-电解循环实验,在恒电压(1V)条件下,测试了电解反应的电流密度和累积电量的数据,并对循环实验前期、中期、后期的三个阶段煤样品进行了扫描电镜(SEM)、比表面积(BET)、热重(TG)、红外光谱(FT-IR)等表征分析。研究表明,相对于通常煤浆电氧化制氢工艺,这种"两步法"煤浆制氢新工艺具有更高的反应速率,初始电流密度约为60 m A/cm2,而传统的"一步法"煤浆制氢工艺初始电流密度均不超过10 m A/cm~2。表征分析结果很好地反映了煤颗粒在这种制氢工艺过程中的形态、结构、成分的变化,从而解释了在新的煤浆氧化制氢工艺中的Fe~(3+)/Fe~(2+)转化的反应机理。     

Sequential injection spectrophotometric determination of iron as Fe(II) in multi-vitamin preparations using 1,10-phenanthroline as complexing agent

A sequential injection analysis (SIA) system is proposed for the determination of iron (II). Fe(II) was determined by SIA based on the reaction between 1,10-phenanthroline and iron (II), yielding an orange–red colour complex with absorption maximum at 512 nm. The method involved aspiration of 187 μl sample/standard zone followed by a zone of a reagent solution containing 140 μl of 7.8 × 10⁻⁴ mol l⁻¹ 1,10-phenanthroline into a carrier stream to be stacked inside a holding coil and flow reversed through a reaction coil to a detector. The optimum condition was evaluated and the calibration curve is linear over a range of 0.25 to 5.0 mg l⁻¹ of Fe(II) with detection limit of 18 μg l⁻¹. A sample throughput of 40 h⁻¹ was established. This technique is found to be simple, accurate, reproducible and sensitive. The proposed method was successfully applied for the determination of total iron as Fe(II) in pharmaceutical products (multi-vitamin tablets) and is especially useful for the determination of iron (II) in tablets with lower iron (II) contents. The results were found to be in good agreement with the results obtained by manual UV/Vis spectrophotometry and flame atomic absorption spectrometry (FAAS) and with claimed values by the manufacturers.     

PRIOR EXPOSURE OF HUMAN CELLS TO NEAR UV-RADIATION GIVES A DECREASE IN THE AMOUNT OF THE UNSCHEDULED DNA-SYNTHESIS INDUCED BY FAR UV-RADIATION

Pretreatment of human cells with near UV radiation (UVA) in fluences exceeding 5 × 10⁴ Jm⁻² caused a decrease in the amount of the unscheduled DNA synthesis induced by far UV radiation (UVC). The DNA repair synthesis, as measured by the incorporation of [³H] -thymidine, is reduced by nearly a factor of 2 for a UVA radiation exposure of 1.5 × 10⁵ Jm⁻². Since solar UVA fluence rate is rather independent of latitude, this figure corresponds to a UVA exposure time of 50-60 min from noon sunlight in the summer time.     

Novel phosphorus-silicon synergistic flame retardants:Synthesis and characterization

Three novel flame retardants containing both phosphorus and silicon elements in their structures,including[（1,1,3,3- tetramethyl-1,3-disiloxanediyl）di-2,1-ethanediyl]bis（diphenylphosphine oxide）（FR-1）,[（2,4,6,8-tetramethylcyclotetra-siloxane -2,4,6,8-tetrayl）tetra-2,1-ethanediyl]tetrakis[diphenylphosphine oxide]（FR-2） and 1,3,5,7,9,11,13,15-octakis（di-phenylphosphine oxide-2,1-ethanediyl）pentacyclo[9.5.1.1^3,9.l^5,15.1^7,13]octasiloxane（FR-3） were synthesized by a convenient pathway from the reaction of diphenylphosphine oxide（DPPO） and vinyl-terminated siloxanes under the catalysis of triethylborane. The chemical structures of the target compounds were confirmed by nuclear magnetic resonance(¹H NMR,¹³C NMR,²⁹Si NMR and ³¹P NMR),matrix-assisted laser desorption/ionization time-of-flight mass spectrometry（MALDI-TOF-MS） and Fourier transform infrared（FT IR） measurements.Thermogravimetric analysis（TGA） results indicated that the new flame retardants possessed good thermal stability both in nitrogen and in air.FR-3 containing polyhedral oligosilsesquioxanes（POSS） moiety exhibited the best thermal properties with a 10%weight loss temperature>400℃ and a residual weight ratio>39%at 700℃ .     

Ultrasound-assisted extraction of volatile compounds from wine samples: optimisation of the method

This study describes a liquid–liquid extraction technique for extracting volatile compounds from wine using dichloromethane and ultrasounds. This technique permits the simultaneous extraction of different samples with high reproducibility. After the preliminary tests, several parameters (sample volume, solvent volume and extraction time) were optimised using a factorial design to obtain the most relevant variables. The analytical characteristics were obtained such as calibration graphs, detection limits ranging from 0.0238 mg L⁻¹ for 1-pentanol to 0.261 mg L⁻¹ for octanoic acid, quantification limits and relative standard deviation from 2.1 to 6.2%. Extraction yields were calculated giving a range 9.16–1.2%. The optimised conditions were applied to the extraction of samples of young wines from the Denominación de Origen Calificada Rioja category using gas chromatography and a flame ionisation detector.     

Two alkynyl functionalized Co(II)-MOFs as fluorescent sensors exhibiting selectivity and sensitivity for Fe3+ and nitroaromatic compounds

Two alkynyl functionalized 3D frameworks with different structures were successfully synthesized for selective and sensitive detection of Fe³⁺ ions and nitroaromatic compounds through fluorescence quenching.     

催化裂化条件下噻吩与改性Y分子筛的作用机制

以HY、NiY和稀土离子改性的Y分子筛(REY)为研究对象,采用固定床装置评价噻吩模拟油催化裂化性能;运用气相色谱-氢火焰离子发光检测器(GC-FID)、气相色谱-硫化学发光检测器(GC-SCD)和原位红外光谱技术分析产物,关联分子筛的酸性,研究催化裂化条件下噻吩与改性Y分子筛的作用机制。实验结果表明,催化裂化条件下,噻吩与分子筛的作用机制差异主要取决于与B酸或L酸相关的非骨架铝物种或金属离子物种的存在形式。其中,NiY分子筛中,噻吩主要是吸附在与NiOH⁺物种相关的L酸中心,而Ni₄AlO₄³⁺等物种减弱B酸性中心从而降低其裂化性能。对HY来说,噻吩易在与AlO⁺等物种相邻的B酸中心上聚合形成三联噻吩,并发生一定的氢转移和裂化反应;而对REY而言,分子筛中与RE物种相关的L酸位会促进噻吩在与非骨架铝羟基等物种(如Al(OH)₂⁺、Al(OH)²⁺等)相邻的B酸中心形成的二联噻吩发生氢转移和裂化反应。     

Organic fuelled flames in selective ionization detectors for chromatography

Summary The selectivities of two flame-based ionization detectors identified as a Remote FID (RFID) and a Flame Thermionic Ionization Detector (FTID) have been improved by introducing methane as a fuel for the flame. Both the RFID and FTID feature a detector struture in which the ionization polarizer and collector are located several centimeters downstream of an oxygen-rich flame, rather than immediately adjacent to the flame as in a flame ionization detector. The RFID detects long-lived negative ions produced in the flame by the combustion of lead, tin, phosphorus, or silicon compounds. The FTID re-ionizes and detects neutral electronegative products generated by combustion of nitrogen, halogen, or phosphorus compounds. An organic-fuelled RFID can detect 1 pg Pb (Sn, P)/sec with a selectivity of the order of 10⁶ versus hydrocarbons. An organic fuelled FTID is applicable to detection of compounds at nanogram and higher levels. FTID selectivity for PCB compounds in a transformer oil matrix is of the order of 10⁵1. The improved selectivity achieved by using an organic-fuelled flame is also applicable to the detection of phospholipid and other non-volatile N, P, or Cl compounds using an FID/FTID detector accessory for a TLC/FID analyser.     

Synthesis,Crystal Structure,Thermal Decomposition and Sensitivity Properties of (AIM)(HTNR) and (AIM)(PA)

Two new energetic compounds (AIM)(HTNR) and (AIM)(PA)(AIM=2-azidoimidazole, TNR=2,4,6-trinitroresorcinol, PA=picric acid) have been prepared by AIM(2-azidoimidazolium) and TNR(2,4,6-trinitroresorcinol) or PA(picric acid) and characterized by elemental analysis and FTIR spectrum. Their crystal structures were determined by X-ray single-crystal diffraction analysis. The obtained results show that (AIM)(HTNR) crystal belongs to monoclinic, P2₁/c space group, a=1.1306(2) nm, b=0.70305(14) nm, c=1.7398(4) nm, β=106.91°, V=1.3231(5) nm³, D_c=1.778 g/cm³, Z=4, R₁=0.0524, wR₂[I>2σ(I)]=0.1067 and S=1.092 and (AIM)(PA) crystal belongs to monoclinic P2₁/c space group, a=0.80303(16) nm, b=0.81395(16) nm, c=2.0471(4) nm, β=93.93(3)°, V=1.3349(5) nm³, D_c=1.683 g/cm³, Z=4, R₁=0.0784, wR₂[I>2σ(I)]=0.1814 and S=1.098. Both the compounds have electrostatic attraction and hydrogen bonds, which contribute to making the constructions more stable. The decomposition of the two compounds was studied via differential scanning calorimetry(DSC) and thermogravimetry-derivative thermogravimetry(TG-DTG) techniques at a heating rate of 10 ℃/min, and the results show that both the compounds underwent one intensive exothermic decomposition stage. Sensitivity tests reveal that the title compounds were insensitive to friction and impact and sensitive to flame and could be applied in potential pyrotechnics.     

基于二茂铁的两个查尔酮衍生物的合成及超快三阶非线性光学响应

二茂铁是合成新颖有机功能材料的基本单元之一。 本文设计并合成了两个基于二茂铁的同分异构查尔酮衍生物:1-二茂铁基-3-(噻吩-2-基)丙烯酮(a)和1-二茂铁基-3-(噻吩-3-基)丙烯酮(b)。 采用超快激光Z-扫描技术(脉宽180 fs,波长532 nm)测定了化合物a和b的三阶非线性光学性质。 结果表明,化合物a吸收系数β=-2.1×10^-12 m/W,折射率n₂=1.9×10^-19 m²/W,分子超极化率γ=5.37×10^-32 esu;化合物b:β=-1.2×10^-13 m/W,n₂=2.0×10^-19 m²/W,γ=4.48×10^-32 esu。 说明在飞秒激光激发下,电荷转移能够在化合物a和b分子内部快速进行,二者均具有优异的超快三阶非线性光学响应。 在B3LYP/6-311+G(d,p)理论水平下,计算了化合物a和b分子轨道能量、极化率和各基团在前线分子轨道中的占有率。 理论计算结果显示,二茂铁基团在化合物a和b前线分子轨道中占有率分别为97%和98%,对两化合物的非线性光学性能起主导作用。