用多分散高聚物标样作凝胶色谱的分子量分离和扩展效应同时校准

根据凝胶色谱柱在理想工作条件下单分散高分子组分的校准关系与多分散试样的实效关系之间的理论联系,建议了一种简单的觅数方法,同时作凝胶色谱柱的分子量分离和扩展因子的校准。用本法从窄分布的聚苯乙烯和宽分布的1,2-聚丁二烯级分的实验谱图得到的所用凝胶色谱柱的扩展因子与淋出体积间的关系相互重合,与试样种类无关。     

凝胶色谱和1,2聚丁二烯的溶液性质

本工作根据凝胶色谱柱的单分散校准关系和试样的实效关系间的理论联系,建议了一个从一组重均和数均分子量确知的多分散试样的实验谱图,同时订定凝胶色谱柱的分子量校准关系和扩展因子的计算觅数方法。     

凝胶色谱与激光小角光散射联用标定国产窄分布聚苯乙烯

用GPC-LALLS 法测定了国产窄分布聚苯乙烯的三种平均分子量,得到较为准确的多分散指数。经过这样标定的标样可用作GPC柱的分离和扩展效应的校准。测定结果与经典方法进行了对照;同时报道了检测器灵敏度对扩展因子的影响。     

偏最小二乘法及主组分回归法用于药物组分的测定

本文研究了多元校准方法——偏最小二乘法(PLS)和主组份回归法(PCR)在药物多组份光度分析中的应用,获得了较满意的结果。而且在系列校准样品的实验设计、交叉证实法确定最佳因子数以及空缺组份体系的分析等方面进行了探讨。     

凝胶色谱与激光小角光散射联用标定国产窄分布聚苯乙烯

 ]用GPC-LALLS法测定了国产窄分布聚苯乙烯的三种平均分子量，得到较为准确的多分散指数。经过这样标定的标样可用作GPC柱的分离和扩展效应的校准。测定结果与经典方法进行了对照；同时报道了检测器灵敏度对扩展因子的影响。     

研究多嵌段共聚物组成分布的一种新方法

提出一种研究-(A-B)_n-型嵌段共聚物组成分布的新方法。本方法不需任何单分散样品或模型化合物作为标准物质,不需另外进行仪器常数标定,只要求测试过程中仪器常数保持不变。要求样品必须是系列样品,每个样品的平均组成已知或可用其它方法得到,样品个数n≥2,且样品越多越好;对检测器的要求是,两种检测器对不同的嵌段其响应不成比例,响应比差别越大越好。对分离手段的分离机理无要求,只要求样品的分散程度足够大即可。本文还提供了用薄层色谱法研究聚己内酯型聚氨酯多嵌段共聚物的组成分布的实例。     

一种新的样品定量方法——样品加入法

在化学分析中,通常采用的样品定量方法有校准曲线法、标准加入法和标准比较法等.这里介绍一种新方法——样品加入法.样品加入法是将不同已知体积的样品溶液分别加入到已知含量的等份等量的标准溶液中,形成总体溶液(标准溶液+样品溶液)系列,依次测定其观测值.然后采用“最小二乘法”回归求得样品溶液加入体积与总体溶液系列观测值的关系曲线,从而求     

玻璃标样结合硫内标归一定量技术在激光剥蚀-等离子体质谱分析硫化物矿物中的应用

以硬石膏矿物标样中Ca相对于S的灵敏度因子为基准,将玻璃标样中主量和痕量元素相对于Ca的灵敏度因子转换成元素相对于S的灵敏度因子,建立了多玻璃标样结合硫内标归一定量技术分析硫化物单矿物多元素的新方法。利用本方法分析了美国合成多金属硫化物矿物标样MASS-1中20种元素,主量元素分析结果的相对误差小于10%,痕量元素分析结果几乎都落在给定值±不确定度范围内。利用本方法对12个硫化物单矿物分析结果表明,绝大多数主量元素含量测定值的相对误差小于10%,且多数主量元素甚至优于以MASS-1为外标、内标归一定量法及内标校准法分析结果,而痕量元素与MASS-1校准结果较为一致。本方法克服了基体不匹配的问题,能比较准确地定量分析硫化物矿物中的主成分S,可用于定量校准硫化物矿物。     

地下气和水中溶解气的气相色谱空气标定法定量测定

为了改进气相色谱的定量工作,我们定量方法,即所谓空气标定因子法。其理研究并建立了以空气作为基准的气相色谱论与实验依据将另文发表。本文报导这个方法在为地震测报而建立的地下气和水中溶解气分析中的应用。表1列出几种气体在给定条件下的空气标定因子。由下列方程确定气体i的浓度Ci: Ci=Qi(c)·Ai/Aa (1)或 Ci=Φi(c)·hi/ha (2)Qi(c)是气体i浓度的空气标定因子,Φi(c)=Qi(c)·Di/Da;A.h.D 分别为峰面积,峰高和半高峰宽。右下角a,i分别代表标定用的空气和被测气体。地下气和水中溶解气的分析在一台普     

分散固相萃取-气相色谱-串联质谱法测定蔬菜中多环芳烃及卤代多环芳烃

建立了同时检测蔬菜中16种多环芳烃(PAHs)和11种卤代多环芳烃(X-PAHs)污染水平的分散固相萃取-气相色谱-串联质谱(GC-MS/MS)分析方法。样品中的多环芳烃和卤代多环芳烃经正己烷提取,N-丙基乙二胺吸附剂(PSA)和十八烷基键合硅胶吸附剂(C18)分散固相萃取净化剂净化,气相色谱-串联质谱方法测定,外标法定量。16种PAHs和11种X-PAHs在50,100和200μg/kg添加浓度下的回收率为74.7%～115.1%,相对标准偏差为1.6%～15.3%,方法检出限为0.03～7.4μg/kg。     

Short metal capillary columns packed with polymer-coated fibrous materials in high-temperature gas chromatography

The high-temperature gas chromatographic (GC) separation of several semivolatile compounds is studied with a short metal capillary column packed with fibrous material, having a polydimethylsiloxane coating thereon. Taking advantage of the excellent heat-resistance of the fiber and also the combination of the surface-deactivated metal capillary, a temperature-programmed separation up to 450 degrees C is successfully demonstrated for the separation of polymer standard samples. The average molecular weight of the commercially-available polymer standard samples for size exclusion chromatography (SEC) is estimated by high-temperature GC analysis and compared with the nominal value determined by a conventional SEC method. Although a slight deviation for the number-average molecular weight is observed between the GC and SEC analysis, the data for the weight-average molecular weight shows a good agreement in these methods. The results also suggest the future possibility of the fiber-packed metal capillary as a miniaturized GC column with an increased sample loading capacity.     

Mathematical discretization of size-exclusion chromatograms applied to commercial corn maltodextrins

Discretization of a size-exclusion chromatography (SEC) chromatogram is shown here to be an important calculation for characterizing the distribution of a polydisperse polymer, especially when the polydispersity is large. Commercial poly-glucose maltodextrins are known to have such a polydispersity. A mathematical discretization method with Gaussian peaks centered on each individual degree of polymerization is proposed and is performed on the entire SEC chromatogram for three different grades of corn maltodextrins. Because SEC and high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) are based on different separation mechanisms, they can be considered orthogonal techniques, and HPAEC-PAD was therefore used to validate the SEC discretization procedure. Because this validation proved satisfactory for all commercially available oligomers, the discretization is extended to all of their SEC chromatograms. Comparing the number-average molar weight and the weight-average molar weight before and after the mathematical discretization verifies that such a mathematical treatment does not denaturate the chromatogram. This approach tentatively leads to a more exhaustive characterization of a broadly polydisperse sample, such as maltodextrins, than was previously available, as it (i) gets rid of the apparent, chemically irrelevant, continuous molar weight distribution obtained by raw SEC and (ii) addresses the current detection and quantitation limits of the HPAEC-PAD technique without any sample treatment.     

The “Fingerprint” of a freshwater microalga Scenedesmus sp. LX1: Visualizing the composition of its soluble algal products

The composition of soluble algal products was visualized by a fingerprint analytical method.     

End-functionalised 1-vinyl-2-pyrrolidinone oligomers bearing lactate functions at one end

1-Vinyl-2-pyrrolidinone (VP) oligomers bearing a lactate group at one end (PVP-L) were obtained by chain-transfer controlled radical polymerisation carried out in the presence of ethyl L-lactate as chain-transfer agent (CTA). Their number-average molecular weights were in the range 1500-4000 with molecular weight distributions ranging from 1.4 to 1.8. The chain transfer constant, C(T), of the ethyl L-lactate/VP system was determined by monitoring the variation of PVP-L number-average molecular weight on conversion. The C(T) value so obtained was 1.03 x 10(-2), which is by about one order of magnitude higher than the C(T) value previously determined for a seemingly similar system, namely methyl isobutyrate/1-vinyl-2-pyrrolidinone (1.64 x 10(-3)). The resultant PVP-L oligomers were thoroughly characterised by means of (1)H and (13)C NMR, in order to ascertain the regular presence of the lactate functions at one of their chain terminals. NMR characterisations gave results in full agreement with the proposed structure. Moreover, the molecular weight values determined by NMR very closely agreed with those obtained by SEC. Preliminary biological evaluations of the PVP-L oligomers showed a complete lack of toxicity.     

稀土络合催化聚合的顺-聚丁二烯的双峰分子量分布

用渗透压、粘度和尺寸排斥色谱方法研究了稀土络合催化聚合的顺丁橡胶在聚合过程中分子量和分子量分布的变化。络合催化剂中不同结构的烷基铝组分在聚合过程中起着不同的作用。对实验数据所作的分析指出,使用烷基铝和氢化烷基铝混合物组成的络合催化剂,聚合至高转化率时的聚丁二烯将出现双峰分布。烷基铝和氢化烷基铝的相反行为指示,聚合机理互有差异,而且不能简单地以链转移常数的不同来解释。     

Molecular weight distributions of industrially-produced poly-(epsilon-caprolactams) by gel permeation chromatography

Gel permeation chromatography with differential refractometry is used to obtain molecular weight distributions (MWD) of poly-(epsilon-caprolactams). Elution is carried out using an m-cresolchlorobenzene mixture (50:50, v/v) at 50 degrees C. MW values are obtained by a Hamielec-based calibration method, using broad-MWD poly-(epsilon-caprolactam) standards with the same chemical nature and similar MWD to the samples. Relative errors for the number-average MW (Mn) using this calibration method range from 0.4% (in the low polyamide MW range) to 20% (in the high polyamide MW range). These values are much lower than those obtained from narrow-MWD polystyrene calibration, which range from 39% to 78%. Similar values have been obtained for the other usual average MW parameters. The ability to obtain repeatability parameters for a given confidence interval and the utilization of statistical criteria for chromatogram rejection allow this method to be used in quality control for MWD of poly-(epsilon-caprolactams). Thus, production variables are related to polyamide-6 behavior in its ulterior treatment. Typical relative standard deviation percentages (for n=6) of a polyamide sample range from 1.9% (for Mn) to 3.3% (for M(z+1)).     

Adamantyl-substituted phenolic polymers

4-(1-Adamantyl)phenol was synthesized via Friedel-Crafts reaction of 1-bromoadamantane and phenol. Substitution in the phenol para position forces polymerization to occur only in the ortho positions to give a linear polymer. Variations in formaldehyde amount, reaction time, and catalyst were evaluated. Increasing the amount of paraformaldehyde increased formation of cyclic octamer, an easily identified by-product due to its insolubility in common organic solvents. The cyclic octamer was acetylated to give a soluble model compound for comparison to acetylated polymers by IR and NMR. All of the synthetic variations employed produced low molecular weight polymers as indicated by NMR end-group analysis and SEC. The polymers showed number-average molecular weights of ca. 3000 (versus polystyrene standards by SEC), and exhibited glass transition temperatures ranging from 175–230°C, an increase of ca. 100°C over unsubstituted and para-alkyl substituted analogs. All of the samples exhibited a 10% weight loss at 400°C in nitrogen, indicating thermal stability much greater than the parent and alkyl-substituted polymers. © 1996 John Wiley & Sons, Inc.     

Size‐exclusion chromatography coupled to multiangle light scattering detection of long‐chain branching in polyethylene made with phillips catalyst

Size‐exclusion chromatography coupled to multiangle light scattering (SEC‐MALS) has been used to detect long‐chain branching (LCB) in polyethylene (PE) from Cr/silica catalysts for the first time. The observed LCB response to several catalyst and reactor variables mostly confirms earlier conclusions drawn from rheological measurements. However, SEC‐MALS has also shed additional light on a few previously unanswered questions. Above all, SEC‐MALS shows the placement of branching within the MW distribution, which was not previously known, and which may explain some of the unique molding behavior of Cr‐derived PE. This new SEC‐MALS data also provide insight into the mechanism of LCB formation, which is discussed. Like earlier studies based on rheology, this new study demonstrates that the commonly accepted view of macromer incorporation may be overly simplistic. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Molecular Weight and Aggregation of Erwinia Gum in Aqueous Solutions

Erwinia(E) gum is composed of glucose, fucose, galactose and glucuronic acid. The weight-average molecular weights Mw, number-average molecular weights Mn and intrinsic viscosities[η] of the four fractions and the unfractionated E gum in aqueous solutions at desired temperatures were studied by light scattering, membrane osmometry, size exclusion chromatography(SEC) and viscometry. The experimental results prove that E gum formed aggregates in the aqueous solution at 25 ℃ and the aggregates were broken gradually with increasing temperature. The dissociation of the aggregates of E gum in the aqueous solution started at 36 ℃, and was completed at around 90 ℃. The [η] values of E gum and its fractions are much higher than those of the conventional polymers with the similar molecular weights, and decrease with increasing NaCl concentration.     

A Method for Following Changes in Molecular Weight Distributions of Polymers on Degradation: Development and Comparison with Ultrasonic Degradation Experiments

When polymers are degraded by submitting them to shearing action, neither the probability of scission of a macromolecule, as a function of molecular weight (MW), nor the probability distribution of the lengths of the resulting fragments is known a priori. Information about these probabilities can be obtained by comparing observed changes in the molecular weight distributions (MWD) of degrading polymer with changes calculated from models. These models are based on assumed functions relating the probabilities mentioned to the MW of the polymer and that of the fragments. In order to make this comparison, equations are derived for various moments of the MWDs in terms of arbitrary initial MWDs and probability functions. Some simplified forms of these equations arising from chosen simple functions for the probabilities are also given. Data are presented to show that the precision of the weight-average MW calculated from gel-permeation chromatography (GPC) is about twice that of the number-average and z-average MW. On the basis of this observation, a particular index is recommended to indicate the shape of MWDs derived from GPC. This index, calculated from the experimental MWDs of degrading polystyrene as a function of degree of degradation, is compared with index curves computed from models with specified forms for the two probability functions. These comparisons suggest that this polymer has a minimum degradable MW of about 40,000. Finally experimental MWDs are shown to agree well with those calculated.