薄层层析酶抑制法测定玉米中克百威的残留量

本方法用丙酮提取、中性氧化铝和活性炭混合柱净化、薄层层析酶抑制法测定,最低检出量1纳克,最小检知浓度0.0025ppm,残留0.01～1ppm时回收率达90%以上,变异系数小于3.2%。     

合成氨工业气体中微量硫化氢的测定——钼兰比色法

近几年来,随着我国小氮肥工业的迅速发展,一些新型脱硫方法和技术已获得了广泛的应用,使合成氨工业气体中硫化氢的净化率显著提高。一般可脱除硫化氢到100ppm至数ppm,有的可低达1ppm以下。目前生产中,对这种低硫量范围的分析,有库伦电量法、次甲基兰比色法以及萤光光度法,大多仍采用碘量法。碘量法误差颇大,远不能满足生产上的要求,以致往往难于通过化验以达     

气相色谱法测定汽油中的微量水份

采用GDX-104和TDX-02复合固定相,在室温下用庚烷饱和水值作外标,用气相色谱法分析,测定了汽油中<15ppm水份,方法灵敏度达1.2ppm/毫米。讨论了不同载气对测水灵敏度的影响,选样重复性和柱子清洗方法等问题。     

旋流板塔在硫酸尾气回收中的应用与设计

一、前言我厂硫酸车间的生产,长期以来未进行尾气回收,至使排空尾气中二氧化硫达5700ppm以上,远远超过国家规定的排放标准(二氧化硫排放浓度不得大于400ppm)。尾气排放量     

牛奶中DDT和666残留量的简易测定法

本文叙述了一种测定牛奶中DDT和666残留量的方法。该法采用丙酮——正己烷提取,用浓硫酸净化。使添加不同666异构体(0.004—0.008ppm.)和DDT及其代谢物(0.01—0.0ppm)的样品,回收率达83.4％—99.8％。此法简单、快速,且不需要使用昂贵的吸附剂。     

草甘膦原药中钠离子控制的研究

目的:降低草甘膦原药中的钠离子含量,提高产品质量。方法:在单因素试验的基础上,通过正交试验确定生产过程工艺指标和洗涤方式的调整方法,并在生产中得以验证。结果:草甘膦中钠离子指标达500ppm以下的产品合格率达到90%以上。结论:控制草甘膦原药中的钠离子含量在500ppm以下,操作简单可行,可以大规模推广。     

回收甲苯中微量环氧氯丙烷的热导气相色谱分析

以角鲨烷—101白色担体作固定相,热导池为检测器,氢气为载气,改变记录仪满量程,检出环氧氯丙烷量低达100ppm左右;不改变记录仪满量程,加大进料量,最低检出量可到130ppm。若以氮为载气,检出量为150ppm左右     

优选去除油田采出水固体的水力旋流器

设计了几种适用于油田除砂系统所用的小型水力旋流器,并进行了优选实验,得出一种最适合于油田微细颗粒分离的旋流器,这种直径为10mm的旋流器在悬浮液进口浓度为5000ppm时,溢流浓度达240ppm.,修正效率达98.5%。串联使用可广泛用于油田除砂。     

二氧化钛在活性炭纤维上的固定化研究

采用正交设计的方法,研究不同钛源、外加剂及其加入量对二氧化钛在活性炭纤维上负载牢固度的影响,结果表明:负载牢固度最佳方案为钛酸丁酯+聚四氟乙烯(20%),相对流失率为0.0952,负载效果理想;对其进光催化活性实验,120min内,苯浓度从30ppm下降到15ppm左右,降解率达50%,光催化效果显著.     

文东油田防盐工艺的研究与应用

针对文东盐间油井普遍含盐高（2000-6000ppm,最高达200000ppm）的现状,研究了清水洗盐、混气水洗盐、化学清防盐、泡沫洗盐等多种清防盐工艺,这些工艺对文东油田投产早期自喷、气举井的正常生产起到了积极作用,延长了洗盐周期,增加了原油产量。     

Zero migration of monomers in glassy polymers: A possible artifact of thermal depolymerization

Efforts to remove traces of monomers contained in polymers by stripping with steam have resulted in reports that a small concentration of monomer is inextractable, or “locked-in,” the polymer. Any concomitant depolymerization to monomer and diffusive elution of the formed monomer would, in the steady state, result in a constant concentration of monomer within the confines of the polymer. If only the polymer phase were sampled and depolymerization were ignored, this result could be interpreted as an apparent “zero migration” level of monomer. A model that describes the coupled processes of depolymerization and diffusion is presented; predictions and estimates of an apparent “zero-migration” concentration are offered for various polymer/monomer systems considering a variety of kinetic schemes. The effects of temperature, geometry, and sample size on the transient and apparent steady-state, residual-weight fraction of monomer in the polymer are considered. Also, the weight fraction of monomer, neglecting diffusive elution, is estimated for comparison with the steady-state weight fractions calculated for the case in which diffusive elution significantly lowers the residual steady-state monomer level. The results predicted by the model presented are compared with experimental data reported in the literature. Transient approaches to the steady state are included in the model analysis. The steady-state monomer concentrations predicted for polystyrene and poly(acrylonitrile) at 100°C vary from 0.0001 ppm to 100 ppm as the diameter of the respective polymeric spheres varies between 0.5 μ and 500 μ. The predicted steady-state concentrations for vinyl chloride monomer in poly(vinyl chloride) are, under comparable conditions, seven orders of magnitude lower, reflecting the extraordinarily small tendency of polyvinyl chloride to degrade to monomer.     

Minimization of residual monomer content of superabsorbent hydrogels via alteration of initiating system

Production of superabsorbent polymer hydrogels with minimized residual monomer content is an essential prerequisite particularly in their related hygienic, pharmaceutical, and food packaging products. Effect of two thermodissociating initiators and an innovative two‐step initiation approach on the residual monomer content of acrylic acid‐based SAP was preliminarily investigated. Ammonium persulfate (APS) and 4,4′‐azobis(4‐cyanopentanoic acid) (ACPA) were used as water‐soluble initiators for the aqueous solution polymerization. FTIR spectroscopy was used for the structural characterization. It was found that APS was more effective than ACPA, and residual monomer was determined in the range of 2200–3000 and 8900–16,600 ppm for APS‐ and ACPA‐initiated polymerization products, respectively. Residual monomer resulted from APS/tetramethyl ethylenediamine (TMEDA) initiation system was measured to be about 4500 ± 117 ppm for one step initiation. However, a two‐step initiation strategy using the APS‐TMEDA was exposed to be a very effective method to decrease residual monomer to 212 ± 6 ppm. The variation of the hydrogel properties (i.e., gel content, swelling capacity, and the residual monomer content) versus the initiator system and concentration was discussed based on the basic literature and supported by some rheological evidences obtained from rheoanalysis of water‐swollen samples. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of poly(p‐phenylene diamine) and its corrosion inhibition effect on iron in 1M HCl

Water‐soluble poly(p‐phenylene diamine) was chemically synthesized. Its corrosion inhibition performance was evaluated for iron corrosion in 1M HCl at various concentrations, and the results were compared with that of the monomer. The corrosion inhibition properties were evaluated by polarization techniques and electrochemical impedance spectroscopy. The results showed that poly(p‐phenylene diamine) was a more efficient corrosion inhibitor than the monomer and gave an 85% inhibition efficiency at a concentration of 50 ppm, whereas the monomer gave an efficiency of 73% at 5000 ppm. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Desorption of residual monomer from PVC resins in a fluidized bed drier

The present study deals with the investigation of the desorption of vinyl chloride from various commercial and experimental suspension PVC resins in a laboratory fluidized bed drier simulating an industrial drier. The results show that PVC resins may differ widely in the rate at which the monomer is desorbed. The rate of diffusion of the monomer is a function of the drying time, the fluidization air temperature, the porosity, and the amount of glassy particles in the PVC. The residual monomer content decreases with increasing air temperature, drying time, and resin porosity. After 105 min of drying with hot air at 80°C, the residual monomer content in the grade with the highest porosity is reduced from 3400 to 2 ppm, whereas for the grade with the lowest porosity, it is reduced from 4300 to 172 ppm on a dry basis. It appears that the resins of the high molecular weight grades are more porous and the low molecular weight grades contain a high proportion of nonporous or glassy particles and, hence, the desorption rate is smaller in these grades. The proportion of glassy particles and the size of glassy domains are estimated in this study by applying the experimental desorption data at long times to a desorption model. The model is useful in differentiating the interior structure of various PVC grades. © 1994 John Wiley & Sons, Inc.     

13C n.m.r. determination of units formed by irregular addition in polyisoprene

¹³C n.m.r. spectroscopic data obtained for model compounds imitating regular and irregular addition of monomer units in linear polyisoprene are compared with the chemical shifts calculated using the empirical regularities found for the branched alkanes and alkenes and a good correlation is established. The validity of the results obtained was confirmed by investigation of the carbon spectra of hydrogenated and unhydrogenated polyisoprenes which contain chain fragments with irregular addition of units. Samples of hydrogenated polyisoprene are shown to give resonance lines that correspond to the methylene carbons of head-to-head and tail-to-tail addition and show chemical shifts at 34.62 ppm and 27.61 ppm, respectively. For the unhydrogenated polyisoprenes, the methylene carbons of trans- and cis-units in head-to-head addition were found to absorb at 38.6 ppm and 31.4 ppm, respectively, with those in the tail-to-tail addition of both isomers absorbing at 28.4–28.8 ppm. The latter findings offer a practical means of characterizing irregularities in polyisoprenes.     

Mass transfer and depolymerization of styrene in polystyrene

This work shows how laboratory experiments may provide parameters which are useful in modeling a commercial process of polystyrene devolatilization. Such processes often occur at temperatures where depolymerization of polystyrene to monomer may be significant. Polystyrene devolatilizers function by forming thin films of the polymer, with styrene loss by flashing and diffusion and styrene generation by depolymerization. The modeling parameters of importance are: depolymerization rate constant, monomer diffusivity, and thermodynamic equilibrium polymer-vapor partition coefficient. Typical levels of styrene in polystyrene in the last stage of devolatilization are 100 to 1000 ppm. Pressures and temperatures in the devolatilizer are often less than 10 torr and greater than 200°C. For styrene-polystyrene the desired parameters have not been reported, nor apparently measured, at the concentration, pressure and temperature levels of interest.     

Residual monomer in superabsorbent polymers: Effects of the initiating system

Minimized residual monomer is an essential requirement particularly in hygienic, pharmaceutical, and food packaging polymer products such as superabsorbent polymers (SAPs). The present article is the first non‐patent report on the study of a highly effective polymerization variable (e.g. initiator) on the residual monomer of SAPs based on partially neutralized acrylic acid. Two persulfate systems, i.e. ammonium persulfate (APS)/sodium metabisulfite (SMBS) and APS/tetramethyl ethylenediamine (TMEDA), were examined to initiate the free‐radical polymerization at room temperature. It was shown that chromatographically measured residual monomer and swelling capacity was strongly dependent on the type and concentration of the initiator. A kinetic model was also derived to describe the experimental results. Dissociation rate of initiation system was recognized to be a key factor to obtain a SAP with low residual monomer. It was found that, in aqueous solution polymerization, the effect of a slowly dissociating system such as APS/TMEDA on decreasing the residual monomer was much higher than that of a rapidly dissociating system like APS/SMBS. Under selected conditions, residual monomer could be reduced up to 5327 ± 138 and 1715 ± 44 ppm for APS/SMBS and APS/TMEDA initiating systems, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The Effect of ppm-Level Na Impurity on the Structure of SiO2-Supported Mo Catalysts Prepared in a Clean Room

To investigate the effect of alkali impurity in Mo/SiO₂ on the MoO _x structure on SiO₂ surfaces SiO₂-supported Mo oxides were prepared with various amounts of Na ions in a class-1 clean bench with a laminar flow in a class-1000 clean room. The Na concentrations were varied in the range 0-5000 ppm, while the Mo loading on SiO₂ was maintained at 0.7 wt%. The Mo-Na/SiO₂ samples obtained were characterized by diffuse reflectance UV-visible and Raman spectroscopy. Three types of Mo species were identified: octahedral monooxo Mo monomer species, Na₂Mo₂O₇ and MoO₃. At less than 100 ppm Na both octahedral Mo monomers and MoO₃ species were formed on SiO₂. The MoO₃ species was transformed to Na₂Mo₂O₇ at 2000 ppm Na, where the Na ions interact directly with the Mo species on the surface. The octahedral monooxo Mo monomer species seems not to be influenced significantly by Na impurity.     

The migration of vinyl chloride monomer from PVC pipe into water

A study was undertaken to determine the extent of residual vinyl chloride monomer (VCM) migration from PVC pipe into water. Methods were developed to analyze VCM in water at low levels. Test samples of PVC pipe were exposed to water under static and flowing conditions for varying time intervals. The results indicate that the level of VCM extracted into water is directly proportional to the level of residual monomer in the pipe. Pipe containing <1.0 mg/kg(<1.0 ppm) residual VCM showed no VCM extracted into water with a test sensitive to 0.002 mg/kg (2 ppb).