纺织品、皮革及其制品中五氯苯酚残留量的气相色谱-质谱法测定

介绍应用气相色谱-质谱法测定纺织品、皮革及其制品中防霉剂五氯苯酚的残留量,试样经硫酸溶液酸化后用正己烷提取,用气相色谱-质谱选择离子测定。方法简便、快速、灵敏,检出限20μg／kg,添加回收率86．7％～93．1％,变异系数4．1％～5．9％。     

Quantitative thermodynamic analysis of sublimation rates using an atomic force microscope

Atomic force microscopy (AFM) has been successfully used to study the activation energy for evaporation of pentaerythritol tetranitrate (PETN) nanoislands formed by spin coating. These islands are annealed isothermally in the temperature range of 30-70 degrees C for a given time and are scanned with AFM in contact mode at room temperature. The volume of these islands does not change significantly up to about 35-40 degrees C indicating that sublimation is not significant below 40 degrees C. Above 40 degrees C, the islands start shrinking, and the rate of weight loss is analyzed as a function of temperature. The activation energy of evaporation using AFM was found to be similar to that for bulk PETN crystals using thermogravimetric analysis (TGA) at higher temperatures (110-135 degrees C). These results demonstrate that AFM is a useful tool to measure thermodynamic properties with a nanoscale probe.     

Analysis of methyl tert.-butyl ether and its degradation products by direct aqueous injection onto gas chromatography with mass spectrometry or flame ionization detection systems.

A method was developed to analyze methyl tert.-butyl ether (MTBE) and its degradation products by gas chromatography with mass spectrometry (GC-MS) or flame ionization detection (FID) with direct aqueous injection. The column had dimensions of 30 m x 0.25 mm with film thickness 0.25 microm and a stationary phase of FFAP (nitroterephthalic acid-modified polyethylene glycol). The optimized GC conditions for non-acid components were as follows: carrier gas flow-rate,l mL/min; oven temperature, 35 degrees C for 5.5 min, ramped to 90 degrees C at 25 degrees C/min, then ramped to 200 degrees C at 40 degrees C/min and held at 200 degrees C for 8 min. The conditions for the acid components were: carrier gas flow-rate, 1 mL/min; oven temperature, 110 degrees C for 2 min, ramped to 150 degrees C at 10 degrees C/min, then ramped to 200 degrees C at 40 degrees C/min. The injection port contained a silanized-glass reverse-cup liner filled with Carbofrit. The minimum concentrations for the linear range for the selective ion monitoring mode were 30 to 100 microg/L, depending on the analytes. The minimum detection limit was 1 mg/L for MTBE and tert.-butanol when using FID. More components could be analyzed with the FFAP-type column than with the cyanopropylphenyl-dimethyl polysiloxane-type column.     

Surface structure relaxation of poly(methyl methacrylate)

Surface structure relaxations caused by temperature changes at the free surface of poly(methyl methacrylate) were studied using IR-visible sum-frequency generation (SFG). A polarization-rotating technique was introduced to enhance the sensitivity of SFG for monitoring the surface structure relaxations during a cooling process. A new surface structure relaxation was observed at 67 degrees C. This temperature does not match any known structure relaxation temperatures for the bulk and is 40 degrees C below the bulk glass transition temperature. As expected for a free-surface phenomenon, the surface relaxation temperature was found to be independent of film thickness in the range of 0.1-0.5 microm.     

大气有机物预浓缩用吸附剂富集特性的气相色谱法研究

用气相色谱方法研究了吸附剂对大气有机物的富集特性,提出用吸附参数泄漏体积ＢＴＶ（最大采样体积）以及脱附参数最低脱附温度或最小吹扫体积作为富集指标的新思想,并用冲洗色谱法测定了一些有机物在ＧＤＸ－３０１上的特性参数。不同温度的特性参数由１ｏｇ（ＢＴＶ）与１／Ｔｃ的线性关系外推得到。实验表明,所研究的２０种有机物（除了甲醇外）在装有２ｇＧＤＸ－３０１的采样管和０．１４ｇＧＤＸ－３０１的聚焦管上的最大采样体积分别不小于０．８Ｌ（３５℃）和０．３Ｌ（０℃）。     

应用搅拌棒吸附萃取-热脱附-气相色谱-质谱分析烟用香料的化学成分

应用搅拌棒吸附萃取法(SBSE)提取烟用香料的化学成分,并利用热脱附(TD)和色谱-质谱联用(GC-MS)进行分析。对影响萃取效果的因素(萃取时间和氯化钠的加入量)进行了考察,并采用正交试验法对影响热脱附的3个主要因素(脱附温度、脱附时间和冷阱温度)进行了优化,得到了较优的实验条件。对方法的重现性进行了考察,同一样品6次测定所得30个组分的峰面积的相对标准偏差（RSD）平均值小于10%,说明所建立方法的重现性较好。在样品中鉴别出酯类、酮类和醛类等30种不同化学组分,这些物质反映了该香料的香气特点。实验证明SBSE和TD适用于烟用香料的快速分析测定。     

Determination of optimum conditions for the analysis of volatile components in pine needles by double-shot pyrolysis-gas chromatography-mass spectrometry

The optimum conditions for the analysis of the volatile organic components of pine needles from Pinus densiflora using double-shot pyrolysis-gas chromatography-mass spectrometry (DSP-GC-MS) were investigated with respect to thermal desorption temperature and duration of heating. A total of 41 compounds were identified using thermal desorption temperatures of 150 degrees C, 200 degrees C, 250 degrees C and 300 degrees C. Thermal decomposition products, which include acetol, acetic acid, furfurals and phenols, were observed only at thermal desorption temperatures exceeding 250 degrees C: they were not observed in the extract from a simultaneous distillation extraction (SDE) method. Heating times of 1 s, 6 s, 30 s, 150 s and 300 s were investigated at the thermal desorption temperature of 200 degrees C, whence it was found that thermal decomposition products were produced only at heating times over 30 s. The optimum pyrolyzer conditions for the analysis of pine needles using DSP-GC-MS is 200 degrees C for 6 s. Under these conditions, this method gives comparable results to the SDE method.     

Effects of temperature and endogenous factors in blood on concentrations of cyclosporin in plasma measured by high-performance liquid chromatography

The effects of temperature, hematocrit (Hct), lipid level in plasma and cyclosporin A (CyA) level in whole blood on the concentration of CyA in plasma measured by high-performance liquid chromatography were studied in vitro. With rise in blood storage temperature before cells were removed, the concentration of CyA in plasma was increased in the temperature range between 10 degrees C and 37 degrees C, but was decreased between 4 degrees C and 10 degrees C. With rise in Hct, the concentration of CyA in plasma was decreased, and it was more markedly decreased at the blood storage temperature of 4 degrees C than at 37 degrees C. A lipid supplementation study showed that the concentration of CyA in plasma was increased with rise in plasma triglyceride level and in plasma cholesterol level at the storage temperature of 4 degrees C but not at 37 degrees C. Studies of the effect of CyA concentration in blood on the CyA distribution in blood demonstrated that the cellular/plasma concentration (C/P) ratio at low levels (less than 200 micrograms/ml) of plasma CyA ranged from 4 to 10 and was about 2 times higher than that at higher concentrations at 4 degrees C, but the ratio was relatively constant at 37 degrees C. The saturation capacity of the cellular fraction for CyA showed considerable individual variations, but there was no difference between the capacities at 4 degrees C and 37 degrees C. The separation of plasma after equilibration at 37 degrees C made it possible to avoid the variations in the distribution of CyA in whole blood associated with changes in Hct, lipid level in plasma and CyA level in whole blood, and to obtain a measurement reflecting the physiologically significant concentration of CyA in plasma.     

A new high-temperature multinuclear-magnetic-resonance probe and the self-diffusion of light and heavy water in sub- and supercritical conditions

A high-resolution nuclear-magnetic-resonance probe (500 MHz for 1H) has been developed for multinuclear pulsed-field-gradient spin-echo diffusion measurements at high temperatures up to 400 degrees C. The convection effect on the self-diffusion measurement is minimized by achieving the homogeneous temperature distributions of +/-1 and +/-2 degrees C, respectively, at 250 and 400 degrees C. The high temperature homogeneity is attained by using the solid-state heating system composed of a ceramic (AlN) with high thermal conductivity comparable with that of metal aluminium. The self-diffusion coefficients D for light (1H2O) and heavy (2H2O) water are distinguishably measured at subcritical temperatures of 30-350 degrees C with intervals of 10-25 degrees C on the liquid-vapor coexisting curve and at a supercritical temperature of 400 degrees C as a function of water density between 0.071 and 0.251 gcm3. The D value obtained for 1H2O is 10%-20% smaller than those previously reported because of the absence of the convection effect. At 400 degrees C, the D value for 1H2O is increased by a factor of 3.7 as the water density is reduced from 0.251 to 0.071 gcm3. The isotope ratio D(1H2O)D(2H2O) decreases from 1.23 to approximately 1.0 as the temperature increases from 30 to 400 degrees C. The linear hydrodynamic relationship between the self-diffusion coefficient divided by the temperature and the inverse viscosity does not hold. The effective hydrodynamic radius of water is not constant but increases with the temperature elevation in subcritical water.     

New low-index liquid refractive index standard: SRM 1922

A new standard for the calibration of refractometers has been developed. Standard Reference Material (SRM) 1922 is a mineral oil with a refractive index nD = 1.46945 at 20 degrees C, which is within the range of the Brix scale (% sucrose). The change in refractive index with temperature (dn/dT) has been characterized for the range 15 degrees C to 35 degrees C to allow for calibrations within that range of temperatures. The refractive indices were measured at 5 wavelengths in the visible spectrum by using the method of minimum deviation with a +/- 2-3 x 10(-5) uncertainty at 20 degrees C. The values of nD and dnD/dT were determined by fits of a two-term Cauchy function to the values at the measured wavelengths with a +/- 6 x 10(-5) uncertainty in nD at 20 degrees C.     

Salt effect on the heat-induced association behavior of gold nanoparticles coated with poly(N-isopropylacrylamide) prepared via reversible addition-fragmentation chain transfer (RAFT) radical polymerization

Poly(N-isopropylacrylamide) (PNIPAM) with a narrow molecular weight distribution was prepared by reversible addition-fragmentation chain transfer (RAFT) radical polymerization. A dithioester group at the chain end of PNIPAM thus prepared was cleaved by treating with 2-ethanolamine to provide thiol-terminated PNIPAM with which gold nanoparticles were coated via reactions of the terminal thiol with gold. The thermoresponsive nature of the maximum wavelength of the surface plasmon band and hydrodynamic radius (Rh) for the PNIPAM-coated gold nanoparticles were found to be sensitively affected by added salt. In pure water, Rh for the PNIPAM-coated gold nanoparticles at 40 degrees C (>lower critical solution temperature (LCST)) was smaller than that at 25 degrees C (相似文献   

Lipase-catalyzed synthesis and properties of poly[(12-hydroxydodecanoate)-co-(12-hydroxystearate)] directed towards novel green and sustainable elastomers

Novel green and sustainable elastomers having both good biodegradability and chemical recyclability properties were designed and synthesized using potentially biobased materials and lipase as an environmentally benign catalyst. High molecular weight poly[(12-hydroxydodecanoate)-co-(12-hydroxystearate)] [poly(12HD-co-12HS)] samples with varying monomer ratios were prepared by the polycondensation of 12-hydroxydodecanoic acid and methyl 12-hydroxystearate using immobilized lipase from Candida antarctica (IM-CA) in toluene in the presence of molecular sieves 4A at 90 degrees C. Although poly(12HD) is a highly crystalline polyester having a melting temperature (T(m)) of 87.6 degrees C and crystalline temperature (T(c)) of 64 degrees C, by the copolymerization of 12HD with 12HS, both the T(m) and T(c) of the copolymer decreased with increasing 12HS contents, and poly(12HD-co-12HS) containing more than 60 mol-% 12HS was a viscous liquid at room temperature. At the same time, the Young's modulus and hardness also decreased with increasing 12HS content, and poly(12HD-co-36 mol-% 12HS) exhibited an elastic behavior, having a hardness of 70 A using a durometer A. In addition, it showed an excellent biodegradability by activated sludge and chemical recyclability by lipase.     

Simultaneous determination of pseudoephedrine hydrochloride and diphenhydramine hydrochloride in cough syrup by gas chromatography (GC)

A simple, rapid and precise gas chromatographic method has been developed for the simultaneous determination of pseudoephedrine hydrochloride and diphenhydramine hydrochloride in cough syrup, using a SS column of 10% OV 1 on chromosorb W-HP (80-100 mesh) and nitrogen as a carrier gas at a flow rate of 30 ml min(-1). The oven temperature was programmed at 135 degrees C for 1 min, with a rise of 10 degrees C min(-1) up to 250 degrees C (held for 5 min). The injector and detector port temperatures were maintained at 280 degrees C. Detection was carried out using Flame ionization detector. Guaphenesin was used as an internal standard. Results of assay and recovery studies were statistically evaluated for its accuracy and precision.     

On-chip temperature gradient interaction chromatography

This paper reports the first integrated microelectromechanical system (MEMS) HPLC chip that consists of a parylene high-pressure LC column, an electrochemical sensor, a resistive heater and a thermal-isolation structure for on-chip temperature gradient interaction chromatography application. The separation column was 8 mm long, 100 microm wide, 25 microm high and was packed with 5 microm sized, C18-coated beads using conventional slurry-packing technique. A novel parylene-enhanced, air-gap thermal isolation technology was used to reduce heater power consumption by 58% and to reduce temperature rise in the off-column area by 67%. The fabricated chip consumed 400 mW when operated at 100 degrees C. To test the chromatography performance of the fabricated system, a mixture of derivatized amino acids was chosen for separation. A temporal temperature gradient scanning from 25 to 65 degrees C with a ramping rate of 3.6 degrees C/min was applied to the column during separation. Successful chromatographic separation of derivatized amino acids was carried out using our chip. Compared with conventional temperature gradient HPLC system which incorporates "macro oven" to generate temporal temperature gradient on the column, our chip's thermal performance, i.e., power consumption and thermal response, is greatly improved without sacrificing chromatography quality.     

DNA mutation detection with chip-based temperature gradient capillary electrophoresis using a slantwise radiative heating system

A simple and robust chip-based temperature gradient capillary electrophoresis (TGCE) system was developed for DNA mutation/single-nucleotide polymorphism (SNP) analysis using a radiative heating system. Reproducible, stable and uniform temperature gradients were established along a 3 cm length of the electrophoretic separation channel using a single thermostated aluminium heater plate. The heater was slightly slanted relative to the plane of the glass chip at 0.2-1.3 degrees by inserting thin spacers between the plate and chip at one end to produce differences in radiative heating that created the temperature gradient. On-chip TGCE analyses of 4 mutant DNA model samples amplified from plasmid templates, each containing a single base substitution, with a wide range of melting temperatures, showed that mutations were successfully detected under a wide temperature gradient of 10 degrees C and within a short gradient region of about 3 cm (3.3 degrees C cm(-1) gradient). The radiative heating system was able to establish stable spatial temperature gradients along short microfluidic separation channels using simple peripheral equipment and manipulation while ensuring good resolution for detecting a wide range of mutations. Effectiveness of the system was demonstrated by the successful detection of K-ras gene mutations in 6 colon cancer cell lines.     

Separation of steroids using temperature-dependent inclusion chromatography

The influence of temperature on retention and separation of estrogens, progesterone derivatives and beta-cyclodextrin in reversed-phase high-performance liquid chromatography has been studied. Steroids were detected using direct UV detection at 240 and 280 nm. Detection of beta-cyclodextrin was achieved using a post-column indirect photometric method. Chromatographic experiments were performed using an acetonitrile-water mobile phase (30%, v/v) and a wide range of column temperatures from 0 to 80 degrees C with 20 degrees C steps. Linear Van't Hoff plots were observed for steroids and beta-cyclodextrin when an unmodified binary mobile phase was applied. The retention of steroids was strongly influenced by temperature when the mobile phase was modified with beta-cyclodextrin at a concentration of 12 mM. Particularly, for 17beta-estradiol and 20alpha-hydroxyprogesterone a strong deviation from the linear Van't Hoff plots and a remarkable affinity for beta-cyclodextrin was observed. Polynomial regression calculations were performed to fit the set of experimental data points. Using third-order polynomial equations, minimum separation factor values (alphamin) were calculated for temperatures from -10 to + 100 degrees C with 1 degrees C steps. The best chromatographic conditions for separation of multicomponent samples were chosen. A possible retention mechanism for solutes in the presence of macrocyclic additives is discussed. The results presented describe the role of temperature in high-performance liquid chromatography systems in which the mobile phase is modified with an inclusion agent.     

Analysis of amino acids without derivatization in barley extracts by LC-MS-MS

A method has been developed for quantification of 20 amino acids as well as 13 (15)N-labeled amino acids in barley plants. The amino acids were extracted from plant tissues using aqueous HCl-ethanol and directly analyzed without further purification. Analysis of the underivatized amino acids was performed by liquid chromatography (LC)-electrospray ionization (ESI) tandem mass spectrometry (MS-MS) in the positive ESI mode. Separation was achieved on a strong cation exchange column (Luna 5micro SCX 100A) with 30 mM ammonium acetate in water (solvent A) and 5% acetic acid in water (solvent B). Quantification was accomplished using d (2)-Phe as an internal standard. Calibration curves were linear over the range 0.5-50 microM, and limits of detection were estimated to be 0.1-3.0 microM. The mass-spectrometric technique was employed to study the regulation of amino acid levels in barley plants grown at 15 degrees C uniform root temperature (RT) and 20-10 degrees C vertical RT gradient (RTG). The LC-MS-MS results demonstrated enhanced concentration of free amino acids in shoots at 20-10 degrees C RTG, while total free amino acid concentration in roots was similarly low for both RT treatments. (15)NO(3) (-) labeling experiments showed lower (15)N/(14)N ratios for Glu, Ser, Ala and Val in plants grown at 20-10 degrees C RTG compared with those grown at 15 degrees C RT.     

山楂挥发性化合物的气相色谱-质谱分析

采用蒸馏－萃取法收集山楂果的挥发性化合物,通过气相色谱及气相色谱／质谱分析,鉴定了３２种化合物,占总峰面积的６１％～６８％。其中主要的１０种化合物是顺－３－己烯醇、顺－３－乙酸己烯酯、α－萜品醇、糠醛、己醇、乙酸己酯、壬醛、柠檬醛、３－戊烯－２－酮,反－２－癸烯醛等。     

Rapid high-resolution electrophoresis of multimeric von Willebrand Factor using a thermopiloted gel apparatus

Rapid and highly reproducible nonreducing agarose gel electrophoresis (NRAGE) of von Willebrand Factor (vWF) multimers was performed using a thermostated minigel apparatus that monitors and precisely controls internal gel temperature. The substitution of lithium dodecyl sulfate (LiDS) for sodium dodecyl sulfate (SDS) allowed electrophoresis to be performed below the 16 degrees C Krafft point of SDS and facilitated NRAGE of vWF over the entire range of 0-35 degrees C. Internal gel temperature was regulated by a thermocouple probe inserted directly into the gel during electrophoresis which interfaced with a thermopilot that continually measures and adjusts temperature to within +/- 0.5 degrees C. At 10 degrees C operative temperature, NRAGE at 1.5% agarose concentration was completed in 20 min at 250 V. Electrophoresis could be performed in only 10 min at 500 V, but at such high voltages, localized temperature fluctuations as much as 6 degrees C resulted in perturbation of banding patterns in those vicinities. In the optimized method, both high molecular weight multimers and proteolytic fragments of vWF were separable suggesting clinical applicability of this system for the diagnosis of von Willebrand Disease and thrombotic thrombocytopenic purpura.     

Quantitative calibration of vapor levels of TNT, RDX, and PETN using a diffusion generator with gravimetry and ion mobility spectrometry

A prototype generator for creating a continuous stream of explosive vapor was referenced quantitatively both to a standard weight from the National Institute of Standards and Technology (NIST) and to the response of an ion mobility spectrometer. Vapors from solid explosive, in a precision bore glass tube at constant temperature, diffuse into an inert gas flow. Mass output rates were determined by (1) sample temperature, and (2) sample tube dimensions (length and cross-sectional area). A reference to NIST was achieved gravimetrically though a microbalance calibrated with a reference weight; mass output rates were obtained for 2,4,6-trinitrotoluene (TNT), cyclotrimethylenetrinitramine (RDX) and pentaerythritol tetranitrate (PETN) at three or more oven temperatures between 79 degrees C and 150 degrees C. The mass output rate was stable over hundreds of hours of continuous operation and the output was adjustable from a few picograms per second to several nanograms per second through variation of the oven temperature. An independent calibration of the vapor generator for TNT at 79 degrees C using an ion mobility spectrometer matched exactly the gravimetric-based findings. In most instances, measured mass output rates compared favorably with theoretically calculated mass output rates, with discrepancies in a few cases resulting primarily from uncertainties in terms (vapor pressures and diffusion coefficients) used to perform the calculations. Agreement is generally not good for PETN, where molecular decomposition contributed to higher than expected measured mass outputs.