丙二醇甲醚中超痕量金属杂质元素的ICP-MS/MS分析

基于电感耦合等离子体串联质谱(ICP-MS/MS)建立了准确测定丙二醇甲醚中超痕量金属杂质元素的分析方法,提出了利用混合反应气消除质谱干扰的新策略.丙二醇甲醚经超纯水稀释后直接采用IC P-MS/MS测定其中具有挑战性的超痕量金属元素Mg,Al,K,Ti,V,Cr,Fe,Ni,Cu和Zn,在MS/MS模式下,选择混合气...     

高灵敏的连续激光光腔衰荡光谱仪及其应用

基于连续可调谐的钛宝石激光光源,建立了光腔衰荡光谱(CRDS)装置,实验表明,其不但具有10-4cm-1的光谱分辨率,测靖灵敏度也好于10-10·cm-1.通过对C2H2气体在12 696.4 cm-1附近的吸收光谱测量,验证了该装置的定量测量能力,并通过对混有痕量C2H2气体的氮气样品的光谱测量,表明该装置对C2H2...     

甲基乙基亚硫酸与亚氨基负离子多组分反应及机理的理论研究

采用分子动力学方法研究了一系列同比例(5:5,10:10,20:20,50:50)和不同比例(20:30,20:40,20:50和30:20,40:20,50:20)的亚氨基负离子与甲基乙基亚硫酸的反应显示,有较多的亚氨基转化为氨气,同时甲基乙基亚硫酸分解为甲醇、乙醇和一些小的碳化合物等物质.通过密度泛函的B3lyp和Bhandhlyp两种方法,在6-311++G(3df, 3pd)水平下对其反应机理进行研究表明,此反应为多通道多步骤的反应体系,无论主反应还是次反应均为放热反应,其中生成产物为P1(CH₃OSO₂~-+NH₃+C₂H₄),P2(CH₃OSO₂~-+NH₂CH₂CH₃),P3(CH₂O+SO₂+NH₃+C₂H₅~-)的路径为最佳反应通道,而生成P4...     

Optical parametric oscillator based off-axis integrated cavity output spectroscopy for rapid chemical sensing

An optical parametric oscillator (OPO), pumped by a fiber-amplified diode laser, is combined with off-axis integrated cavity output spectroscopy (OA-ICOS). The cw OPO (power 1.2 W, tunability 3-4 μm, 5 cm(-1) mode-hop-free tuning) has a tuning speed of 100 THz/s, which is ideal for rapid and sensitive trace gas detection. Combined with OA-ICOS, a detection limit of 50 parts per trillion by volume (1×10(12)) of ethane (C(2)H(6)) in nitrogen was obtained in 0.25s at 2997 cm(-1), corresponding to a noise equivalent absorption sensitivity of 4.8×10(-11) cm(-1) Hz(-1/2). The system demonstrates real-time measurements of methane and water in exhaled human breath.     

Direct determination of the Boltzmann constant by an optical method

We have recorded the Doppler profile of a well-isolated rovibrational line in the nu(2) band of (14)NH(3). Ammonia gas was placed in an absorption cell thermalized by a water-ice bath. By extrapolating to zero pressure, we have deduced the Doppler width which gives a first measurement of the Boltzmann constant k(B) by laser spectroscopy. A relative uncertainty of 2 x 10(-4) has been obtained. The present determination should be significantly improved in the near future and contribute to a new definition of the kelvin.     

铁(Ⅲ)的硅胶H相反射散射光度法研究

本文提出了胡椒基荧光酮 (PIF)硅胶H相反射散射光度法测定铁的新方法。在溴化十六烷基三甲基铵的存在下 ,PIF与铁 (Ⅲ )形成稳定的蓝色配合物并且能被硅胶H吸附 ,其最大反射散射吸收波长位于 6 4 0nm ,铁 (Ⅲ )的浓度在 0～ 2 5ng·mL- 1 范围内呈线性关系 ,方法用于氧化镁中微量铁的测定 ,结果满意。     

Cs(6DJ)+(H2,He)的反应与非反应碰撞能量转移

在样品池条件下,利用原子荧光光谱方法,测量了Cs(6DJ)与H2,He碰撞中的反应与非反应能量转移截面.利用脉冲激光886nm线双光子激发Cs(6S)到Cs(6D3/2)态,原子荧光中除含有6D3/2→6P的直接荧光外,还含有6D5/2→6P的转移荧光.利用三能级模型的速率方程分析,在不同的He和H2密度下,分别测垦直接荧光与转移荧光的时间积分荧光强度比,得到了6D3/2与H2和He碰撞的精细结构转移截面分别为σ=(55±13)×10-16和(16±4)×10-16 cm2,同时确定了6D5/2与H2和He的碰撞猝灭速率系数.6D5/2态与H2的碰撞猝灭速率系数比6D5/2与He的大,它是反应与非反应速率系数之和,利用实验数据确定非反应速率系数为6.3×10-10 cm3·s-1,得到6D5/2与H2的反应截面为(2.0±0.8)×10-16 cm2.利用不同H2(或He)密度下6D5/2→6P3/2时间积分荧光强度,得到6D3/2与H2反应截面为(4.0±1.6)×10-16 cm2,6D3/2与H2反应的活性大于6D5/2.     

基于LASSO方法的傅里叶变换红外光谱快速定性识别方法

采用红外光谱技术对未知气体组分进行监测,需要对气体组分进行定性识别分析。基于多元线性回归模型的LASSO变量选择技术广泛应用于数据分析领域。将LASSO方法引入到红外光谱分析领域,提出一种LASSO变量选择技术结合循环线性最小二乘(LCLS)分析的定性识别方法,并开展了相关的实验对其进行验证。实验采集CO,C₂H₄,NH₃,C₃H₈,C₄H₁₀和C₆H₁₄六种单组分傅里叶变换红外(FTIR)光谱吸光度谱以及一组C₂H₄和NH₃混合组分的吸光度谱,结合实验室自建光谱数据库,先采用LASSO方法对采集的光谱进行初步定性分析,然后使用LCLS方法剔除干扰组分。实验结果表明,LASSO结合LCLS的方法能有效识别出光谱中的目标组分,即使是在干扰严重的光谱波段也可以剔除掉大部分的干扰组分。     

Plasma and heat flux characteristics of a supersonic ammonia or nitrogen/hydrogen-mixture direct-current plasma jet impinging on a flat plate

Spectroscopic and electrostatic probe measurements were made to examine plasma characteristics with or without a titanium plate under nitriding for a 10-kW-class direct-current arc plasma jet generator with a supersonic expansion nozzle in a low-pressure environment. Heat fluxes into the plate from the plasma were also evaluated with a Nickel slug and thermocouple arrangement. Ammonia and mixtures of nitrogen and hydrogen were used as a working gas. The NH/sub 3/ and N/sub 2/+3H/sub 2/ plasmas in the nozzle and in the downstream plume without a substrate plate were in thermodynamical nonequilibrium states. As a result, the H-atom electronic excitation temperature and the N/sub 2/ molecule-rotational excitation temperature intensively decreased downstream in the nozzle although the NH molecule-rotational excitation temperature did not show an axial decrease. Each temperature was kept in a small range in the plume without a substrate plate except for the NH rotational temperature for NH/sub 3/ working gas. On the other hand, as approaching the titanium plate, the thermodynamical nonequilibrium plasma came to be a temperature-equilibrium one because the plasma flow tended to stagnate in front of the plate. The electron temperature had a small radial variation near the plate. Both the electron number density and the heat flux decreased radially outward, and an increase in H/sub 2/ mole fraction raised them at a constant radial position. In cases with NH/sub 3/ and N/sub 2/+3H/sub 2/, a radical of NH with a radially wide distribution was considered to contribute to the better nitriding as a chemically active and non heating process.     

Collision-induced vibrational energy transfer: K2[1(1) sigmau+ (nu'=2)]+He, H2-->K2[1(1) sigmau+(nu'=1,3)]+He, H2

Collisional energy transfer processes K2[1(1) sigmau+ (nu'=2)]+He, H2-->K2[1(1) sigmau+(nu'=1,3)]+He, H2 were studied by laser induced fluorescence under gas cell conditions. During the experiments, the cell temperature was kept constant at 420K. The buffer gas pressure was varied over the range from 40 to 250 Pa, Kz molecules were irradiated with pulses of radiation from an OPO laser, populating K2[1(1) sigmau+ (nu'=2)] by photon absorption. The resulting fluorescence included the direct component emitted in the decay of the optically excited state and the sensitized components arising from collisionally populated states. The decay signal of time-resolved fluorescence from 1(1) sigmau+ (nu'=2)]-->1(1) sigmag+(nu"=0) transition was monitored. In the early period after excitation, only very little population in states v'= 1 or 3 had yet accumulated, the rate of collisional activation to the state nu'=2 was negligible. The decay curve of the nu' = 2-->nu" = 0 was treated as a single exponential function. From the measurement of the time-resolved fluorescence, the semilog plot was shown. The slope yielded the effective lifetime of the nu' = 2--> nu' = 0 transition. Based on the Stern-Volmer equation, the radiative lifetime (36 +/- 7) ns was obtained. The total cross sections for deactivation of 1(1) sigmau1 (nu'=2) state by means of collisions with He and H2 are (3.0 +/- 0.5) x 10(-16) cm2 and (6.4 +/- 1.2) x 10(-15) cm2, respectively. The radiative lifetimes of 1(1) sigmau+(nu' = 1,3) states can also be determined through time-resolved fluorescence in pure K vapor. The time-integrated intensities of 1(1)sigmau+(nu' = 1,2,3)-->1(1) sigmag+(nu"=0) transition at different He or Hz pressure were measured. The ratio of fluorescence intensities versus 1/P(He, H2) can be fitted by a straight line. The slopes yield the cross sections sigma(nu'=2-->nu'=1) = (1.4 +/- 0.5) x 10(-16) cm2 and (3.2 +/- 1.0) x 10(-15) cm2; sigma(nu'=2-->nu'=3)= (1.2 +/- 0.4) x 10(-16) cm2 and (2.6 +/- 0.9) x 10(-15) cm2 for He and H2, respectively. Cross sections for the effective quenching of the nu' = 1,2,3 states were also determined. To our knowledge, the cross-sections for these processes are reported for first time.     

Nitridation of Si(100)-( 2x1) surface by NH3: a quantum chemical cluster model study

Based on density functional cluster model calculations, we present the first detailed mechanisms for the complete decomposition of NH3 to NHx(a) (x = 0-2) on the Si(100)-(2x1) surface. Three kinds of elementary processes, namely, N-H bond cleavage, NHx(a) insertion into the Si-Si surface dimer bond or backbond, and H2 libration, are investigated. A plausible microscopic mechanism for the nitridation of Si(100)-(2x1) surface by NH3 is proposed.     

黄酮化合物的偶氮显色反应及其应用研究

在pH 10 4的NH4Cl NH3 ·H2 O缓冲溶液中 ,对磺基氯化重氮苯可与芦丁 ,桑色素 ,染料木甙 ,槲皮素 ,橙皮甙 ,黄岑甙和大豆甙等 7种黄酮化合物发生偶氮显色反应 ,反应产物的最大吸收波长 ,除黄岑甙为 380nm外 ,其余均在 4 30nm ,显色反应的灵敏度依上述顺序逐渐减弱。其中芦丁的摩尔吸收光系数最大 ,为 3 2 8× 10 4L·mol-1·cm-1,大豆甙摩尔吸光系数最小 ,为 8 30× 10 2 L·mol-1·cm-1。提出的分光光度分析方法 ,用于槐米和豆粕中黄酮化合物的测定 ,RSD为 0 2 5 %～ 4 4 8% ,回收率在 99 3%～ 10 5 0 %之间     

High-Resolution Laser Photoacoustic Spectroscopy of HSiF(3): The 5nu(1) and 6nu(1) Overtone Bands

A spectrum of HSiF(3) has been recorded at room temperature with a gas pressure of 20-50 Torr in the near-infrared region. A laser photoacoustic spectrometer consisting of a longitudinal resonant cell coupled to a titanium:sapphire ring laser was employed. The 5nu(1) and 6nu(1) overtone bands of H(28)SiF(3) associated with the Si-H stretching have been observed at high resolution (3 x 10(-2) cm(-1)) in the regions 10 900-10 960 and 12 875-12 925 cm(-1), respectively. About 450 lines of the 5nu(1)-0 band have been assigned (J 相似文献   

GF-AAS法测定处理污水灌溉土壤中铅最佳基体改进剂的选择及其应用

研究了石墨炉原子吸收法（GF-AAS法）测定一级处理污水灌溉土壤中铅最佳基体改进剂的选择及在最佳改进剂条件下测定污水灌溉土壤中铅的GF-AAS法。试验了磷酸二氢铵, 磷酸铵, 氯化铵, Pd-Mg和磷酸二氢铵+硝酸镁+硝酸铵等基体改进剂对测定一级处理污水灌溉土壤铅的基体改进作用,并根据基体改进剂的改进效果,最佳灰化温度和原子化温度, 选定了最佳基体改进剂和测定条件。40 g·L-1的磷酸二氢铵作为基体改进剂,灰化温度为850 ℃,原子化温度为1 600 ℃时,用氘灯校正背景GF-AAS法进行测定,测定方法的RSD为2.6% ,回收率在92.4%～104%之内。     

桑色素合镧(Ⅲ)与核酸作用的荧光光谱及其分析应用

采用荧光法研究了桑色素合镧 (Ⅲ )配合物与核酸的作用。研究了溶液的pH值、缓冲溶液含量、有机试剂、外加干扰离子对桑色素合镧 (Ⅲ )配合物与核酸体系荧光光谱的影响 ,同时还研究了变性DNA与桑色素合镧 (Ⅲ )配合物之间的作用。在溶液 pH =8 0～ 9 0的条件下 ,体系的荧光强度最大 ,最大激发波长为387nm ,最大发射波长为 5 35nm。缓冲溶液的用量控制在 10 % (体积 ) ,乙醇用量也控制在 10 % (体积 )。配合物荧光强度在核酸存在时有所增加 ,据此确定了测定核酸的一种方法 ,简便、快速 ,线性范围宽 ,灵敏度较高 ,结果准确。并对可能的增色效应和酸度对荧光光谱影响的原因进行了讨论。     

15N chemical shift tensor magnitude and orientation in the molecular frame of uracil determined via MAS NMR

The potential of heteronuclear MAS NMR spectroscopy for the characterization of (15)N chemical shift (CS) tensors in multiply labeled systems has been illustrated, in one of the first studies of this type, by a measurement of the chemical shift tensor magnitude and orientation in the molecular frame for the two (15)N sites of uracil. Employing polycrystalline samples of (15)N(2) and 2-(13)C, (15)N(2)-labeled uracil, we have measured, via (15)N-(13)C REDOR and (15)N-(1)H dipolar-shift experiments, the polar and azimuthal angles (θ, psi) of orientation of the (15)N-(13)C and (15)N-(1)H dipolar vectors in the (15)N CS tensor frame. The (θ(NC), psi(NC)) angles are determined to be (92 +/- 10 degrees, 100 +/- 5 degrees ) and (132 +/- 3 degrees, 88 +/- 10 degrees ) for the N1 and N3 sites, respectively. Similarly, (θ(NH), psi(NH)) are found to be (15 +/- 5 degrees, -80 +/- 10 degrees ) and (15 +/- 5 degrees, 90 +/- 10 degrees ) for the N1 and N3 sites, respectively. These results obtained based only on MAS NMR measurements have been compared with the data reported in the literature.     

Low-level and ultralow-volume hollow waveguide based carbon monoxide sensor

We demonstrate an ultralow sample volume optical carbon monoxide sensor with detection sensitivity of 180 parts in 10(9) (1σ at 1 Hz). The utilization of a 2.3 μm surface-emitting laser directly coupled to a 3 m hollow capillary fiber as the gas cell is proven to be a compact, sensitive, and cost-efficient gas sensing concept. By mechanical vibration of the fiber, an absorbance resolution of 10(-5) is achieved, which is comparable to single-reflective (double-pass) cells. An improvement of sensitivity over the conventional single-reflective cell is thus approximately linearly scaled with the enhancement of the optical path length, which is usually more than 1 order of magnitude.     

表面等离子体激元共振溶胶-凝胶薄膜传感器

采用溶胶－凝胶金属氧化物半导体薄膜,作为表面等离子体激元共振效应的光化学传感器的传感介质。分析了金属Ag膜与传感薄膜的光学参数对传感器灵敏度的影响。通过在金属层与传感层之间优化设计中间层,进一步提高了传感器灵敏度。选择SnO2薄膜及SiO2薄膜作为传感层与中间层,对三种气体NH3、C2H5OH、C3H8进行气敏实验,结果表明结构优化的传感器具有更高的灵敏度。     

Observing in-phase single-quantum 15N multiplets for NH2/NH3+ groups with two-dimensional heteronuclear correlation spectroscopy

Two-dimensional (2D) F1-(1)H-coupled HSQC experiments provide 3:1:1:3 and 1:0:1 multiplets for AX(3) and AX(2) spin systems, respectively. These multiplets occur because, in addition to the 2S(y)H(z)(a)-->2S(y)H(z)(a) process, the coherence transfers such as 2S(y)H(z)(a)-->2S(y)H(z)(b) occurring in t(1) period provide detectable magnetization during the t(2) period. Here, we present a 2D F1-(1)H-coupled (1)H-(15)N heteronuclear correlation experiment that provides a 1:3:3:1 quartet for AX(3) spin system and a 1:2:1 triplet for AX(2). The experiment is a derivative of 2D HISQC experiment [J. Iwahara, Y.S. Jung, G.M. Clore, Heteronuclear NMR spectroscopy for lysine NH(3) groups in proteins: unique effect of water exchange on (15)N transverse relaxation. J. Am. Chem. Soc. 129 (2007) 2971-2980] and contains a scheme that kills anti-phase single-quantum terms generated in the t(1) period. The purge scheme is essential to observe in-phase single-quantum multiplets. Applications to the NH(2) and NH(3)(+) groups in proteins are demonstrated.