干扰床分选机(TBS)的评述

介绍了TBS分选机的工作原理,通过对等沉比等参数的研究,分析了澳大利亚斯特拉特福选煤厂TBS分选机的分选效果及工艺流程,指出该类设备只能按照窄粒级分选,工艺流程复杂,生产指标差。     

A simple and efficient SEC/GPC linear calibration technique using broad-range standards

A simple method for calibrating high-performance SEC/GPC systems is presented. This technique sequentially finds the correct slope, D₂, by tracking the calculated polydisperity, P, using arbitrary calibration slopes from which the intercept, D₁, is ultimately back-calculated. The case of application and relative efficiency of this search technique are highlighted and discussed. Theoretical justification of the simple form of the convergence equation is presented using two distribution models—the Gaussian (pseudo-Flory) and the sine (cosine) exponential models. © 1995 John Wiley & Sons, Inc.     

应用电导法测定肥料溶液浓度标准曲线的校验研究

实验室采用大量程电导率仪对高浓度肥料溶液的电导率与溶液浓度的关系进行校验研究,以期通过直接测量肥料溶液电导率值而准确预报溶液中肥料浓度,为快速测定控释肥料静水溶出率(即包膜控释肥料在静水中的释放量)提供理论依据。结果表明,溶液电导率与肥料浓度的直线回归方程和二次曲线回归方程的相关指数(R2)均达到极显著水平,直线回归方程预报值与实测值的标准误差(SE)较大,二次曲线回归方程的标准误差(SE)小,拟合度更高,更准确。     

干扰床分选机(TBS)在张双楼选煤厂的应用

介绍了干扰床分选机(简称TBS)、螺旋分选机、煤泥重介质旋流器等几种粗煤泥分选设备的分选原理和技术特点,结合TBS在选煤工艺设计中的应用实例,说明TBS具有分选密度低、精煤产率高、自动化程度高等优点。     

Number‐average molecular weight of branched polymers from SEC with viscosity detection and universal calibration

BACKGROUND: Number‐average molecular weight, M?_n, is an important characteristic of synthetic polymers. One of the very few promising methods for its determination is size‐exclusion chromatography (SEC) using on‐line viscometric detection and assuming the validity of the universal calibration concept. RESULTS: We have examined the applicability of this approach to the characterization of statistically branched polymers using 22 copolymers of styrene and divinylbenzene as well as 3 homopolymers of divinylbenzene with various degrees of branching. SEC with three on‐line detectors, i.e. concentration, light scattering and viscosity, enables us to evaluate experimental data by various computational procedures yielding M?_n and weight‐average molecular weight, M?_w. Analysis of the results has shown that the universal calibration theorem has limited validity, apparently due to the dependence of the Flory viscosity function on the molecular shape, the molecular weight distribution and the expansion of molecules. CONCLUSION: For complex polymers, the universal calibration, i.e. the dependence of the product of intrinsic viscosity and molecular weight, [η]M, on elution volume, can differ in values of [η]M from those obtained for narrow molecular weight standards by 10–15%. The method studied is helpful for the determination of M?_n of polymers, in particular of those with very broad molecular weight distribution, such as statistically highly branched polymers. Copyright © 2008 Society of Chemical Industry     

Correction for interdetector volume in size exclusion chromatography (SEC)

In a multidetector SEC system it is necessary to match the outputs of the detectors that sense eluant concentration with that are molecular weight dependent. There are several methods to accomplish this. The most common is to determine the interdetector volume or time difference between detectors. The difficulty with this technique is that with detector systems where the column eluent is split, the interdetector time difference varies with solution viscosity. Two new techniques were implemented on a high temperature SEC/DRI/LALLS/VISC system which take into account changes in solution viscosity due to high molecular weight polymers. Both techniques use calibration curves of hydrodynamic volume versus elution volume for the different detectors to determine the “instantaneous” time difference between the detectors as it varies with solution viscosity. Either method provides the correct interdetector time lag information. We note also that in multidetector systems the configuration of the detectors should be such as to maximize solvent flow rates through each detector and hence to minimize band broadening effects. © 1995 John Wiley & Sons, Inc.     

Number-average molecular weight and functionality of poly(tetramethylene glycol) by multidetector SEC

Multidetector size exclusion chromatography (SEC) is used to simultaneously determine molecular weight and number of reactive end groups per chain (functionality) of poly(tetramethylene glycol)s. Hydroxyl groups are first quantitatively derivatized with phenyl isocyanate, providing an end-group-selective UV-absorbing tag. The number of end groups per chain is then determined from the SEC chromatogram using a UV detector. Molecular weight at each retention volume and the number-average molecular weight of the whole polymer are calculated by four methods involving (1) a concentration detector and a narrow standard log M calibration curve, (2) the UV detector and a narrow standard log M calibration, (3) a viscometry detector and a universal calibration curve, and (4) combined differential viscometry and concentration detectors using a universal calibration curve. The multidetector experiment provides a unique opportunity to assess the accuracy and limitations of each approach on low-molecular-weight polymers. In particular, the effect of end groups on the concentration detector response and the application of universal calibration principles at small molecular sizes are important factors. It is shown that the concentration response can be corrected by a simple relationship between detector response and reciprocal molecular weight. Also, the quality of calibration curves is critical to the calculation of accurate molecular weight. In general, log M calibration curves provide superior results to universal calibration methods. © 1995 John Wiley & Sons, Inc.     

JECFA标准介绍（一）

编者按:迄今为止,具有世界最高权威的联合国粮农组织/世界卫生组织(FAO/WHO)的食品法典委员会下的食品添加剂联合专家委员会(简称JECFA)对超过一千多种的食品添加剂的安全性进行了客观评价.为了促进我国食品香精香料行业的规范发展,及时向行业的读者介绍这一有价值的标准体系,从2008年第1期起,我刊将以JECFA评价号的顺序,连续刊发其最新的标准,希望能对整个行业有借鉴和学习作用.     

Comparison of a supercritical fluid extraction method for the extraction of oilseeds with the DGF standard method B-I 5 (87)

Three different oilseeds, rapeseed, sunflower, and soybeans are extracted by SFE (supercritical fluid extraction). As parameter for the extraction conditions the extracts are analyzed regarding the contents of tocopherols, and as parameter for the content of more polar lipids the contents of diglycerides and free fatty acids are analyzed. The extraction temperature has a significant influence on the determined oil content, the content of tocopherols, diglycerides, and free fatty acids. With increasing temperature the oil content increases. The content of tocopherols, diglycerides, and free fatty acids increases up to 75 °C. At 100 °C the content of diglycerides and free fatty acids decreases and the content of tocopherols shows no appreciable changes. The optimal extraction conditions are described and the results of the determination of the oil content under optimal conditions are compared with the results of the DGF standard method B-I 5 (87). The oil contents investigated with both methods correspond well. The content of tocopherols is significantly higher in the oil of rapeseed and soybeans extracted by SFE, whereas the content of diglycerides and free fatty acids varied in dependence on the oilseed.     

Ultrasonic absorption and visco-relaxation study of poly(vinyl alcohol) aqueous solution. (A method for the determination of molecular weight)

Ultrasonic absorption and velocity measurements are reported on aqueous solutions of poly(vinyl alcohol) (PV-OH) of different molecular weights and concentrations obtained using a pulsed ultrasonic apparatus operating at 2 MHz and 303 K. The variations in these parameters as a function of concentration are interpreted in terms of changes in the magnitude of the contribution due to relaxation of the backbone and of the side chain acetyl groups. The results show an increase in velocity, density and viscosity with increase in molecular weight and concentration of PV-OH. In contrast the attenuation values decrease with increase in molecular weight. This suggests that interaction is occurring between PV-OH and water molecules. Deviation of the variation of the attenuation with concentration from the ‘ideal’ dilute solution behaviour at high concentration is ascribed to the effects of polymer-polymer interaction. The magnitude of the volume change associated with polymer-solvent interactions is estimated and discussed. A mathematical equation correlating the relaxation amplitude and the molecular weight of the polymer is suggested. This approach was applied to the calculation of the molecular weight of four unknown samples of PV-OH from their measured relaxation amplitudes. The results obtained agree well with those obtained from osmometry.     

Thermal degradation of poly(ethylene oxide-propylene oxide-ethylene oxide) triblock copolymer: comparative study by SEC/NMR, SEC/MALDI-TOF-MS and SPME/GC-MS

By comparing size exclusion chromatography/matrix assisted laser desorption ionisation (SEC/MALDI) and SEC/NMR spectra from virgin poly(ethylene oxide-propylene oxide-ethylene oxide) triblock copolymer, we were able to understand the bimodal distribution observed in poloxamer 407. Propylene oxide, isomerised to allyl alcohol during polymerisation, eventually forms a Poly(ethylene oxide-propylene oxide) diblock copolymer when EO is added to the feed. The oxidative thermal degradation of poloxamer 407 at 80°C in air was studied. We found by MALDI that degradation starts after 21 days in the PPO block of the copolymer. This result was confirmed by solid phase microextraction/gas chromatography-mass spectrometry (SPME/GC-MS): The first volatile degradation product to appear is 1,2-propanediol,1-acetate,2-formate. The structure of this molecule suggests that a six-ring intramolecular decomposition reaction of the PPO chain occurs at the very beginning of the polymer breakdown. Thus, the secondary hydroperoxide formed on the PPO chain plays a major role on the thermoxidation of poloxamer materials.     

Safety evaluation of microbial pesticide (HaNPV) based on PCR method

Microbial pesticides can prevent and control diseases and pests of crops, and has become one of the important measures to ensure food and environmental safety. However, the potential harm of microbial pesticides to humans and animals is a serious concern at home and abroad. In this paper, we have investigated the infectivity and pathogenicity of a representative of viral microbial pesticides, helicoverpa armigera nuclear polyhedrosis virus (HaNPV), by specific and highly sensitive polymerase chain reaction technology. The results show that HaNPV can be gradually cleared in a short time after getting into blood of experimental rats, and does not infect other tissues or organs of animals;also indicate that the test subjects are not infectious to experimental rats after intravenous injection of HaNPV. Our method has good specificity and repeatability, and could provide an important reference for establishment of infectivity and pathogenicity detection methods for viral microbial pesticides in future.     

GPC calibration for poly(methyl acrylate)

Summary Electrophylic vinyl reagents can be reacted with a protonated tertiary amine supported by a polymeric chain. We determined the mechanism of this addition in the case of vinyl methyl ketone and poly (4 vinyl pyridinium bromide). The first step is the addition of the vinyl compound on the tertiary amine, then protonation of the intermediate species occurs. The velocity constant at 268 K is 0.087 1. mole^–1. mn^–1 and the activation energy is 10 kcal.mole^–1.     

微量甲醛标准溶液的配制与标定分析──以碘量法为例

测定样液中微量甲醛的含量时,需事先配制和标定含微量甲醛的标准溶液.碘量法是标定甲醛溶液的常用方法.为获得具有较好精确度的微量甲醛标准溶液,根据滴定分析原理进行计算后认为,配制质量浓度为1000 mg/L的标准甲醛储备液既适宜标定,也便于稀释应用.在标定中所用的硫代硫酸钠溶液和碘液配制成合适的浓度有利于提高标定甲醛储备液...     

关于超长型温度传感器校准用标准恒温槽研制的探讨

本文主要提出研制一种可校准超长型温度传感器的标准恒温槽的设计要求及设计思路,以供研究探讨,希望解决现实存在的超长型温度传感器因传感器太长而浸没深度不足的校准问题。     

Performance evaluation of three optical particle counters with an efficient “multimodal” calibration method

The sizing accuracies of two widely used yet hitherto unevaluated optical particle counters (OPCs—Grimm Model 1.109 and Palas Model WELAS 2100) as well as one high-resolution, non-commercial OPC were evaluated. The measured data were compared to scattering intensity calculations based on Mie theory. Additionally, the counting efficiency for all three counters was measured, as was the influence of coincidence effects for the OPC with the lowest (manufacturer specified) upper concentration limit.Beside the traditional polystyrene latex calibration, a little-known, very fast and precise “multimodal” calibration method was used, which is based on the simultaneous generation of up to eight sharp multiple-charge modes from polydisperse di-ethyl-hexyl-sebacate (DEHS) particles by electrical mobility classification.     

SEC储量评估方法在普光气田上市储量评估中的应用

普光气田于2005年开始进行产能建设,2007年在美国纽约证券交易所正式上市,目前进入开发投产初期阶段。已经进行了产能建设和开发初期等2个阶段的SEC上市储量评估工作,在不同开发阶段SEC储量评估方法和结果有所不同。通过分析影响评估结果的经济因素和产能因素,明确在不同开发阶段各因素对评估结果的影响程度,提出不同开发对策,用以指导气田下步开发。