Production of a Solvent Yellow 124 “euromarker” reference material certified for purity

Solvent Yellow 124 (SY124, N-ethyl-N-[2(isobutoxyethoxy)ethyl]-4-(phenylazo)aniline) is used as a common low tax fuel marker in European Union member countries. It is added to these fuels which may also contain traditional dyes, to prevent misuse. SY124 is produced industrially in solution (typically aromatic hydrocarbons) and its purity can vary from batch to batch. This is particularly a problem for the petroleum industry which risks large fines if SY124 levels are found to be below 6 mg/L or above 9 mg/L. A new reference material for SY124, certified for purity was prepared to address this problem.A SY124 CRM was prepared from a commercially procured solution of SY124. The details of the preparation and certification will be discussed. The material is commercially available as ERM-AC316a, packaged as 200 mg units in screw cap 4 mL amber glass vials. Its purity value is 95.0 ± 1.2% m/m at the 95% confidence interval.     

A colorimetric method for the molecular weight determination of polyethylene glycol using gold nanoparticles

A gold nanoparticle (AuNP)-based colorimetric method was developed for the molecular weight (MW) determination of polyethylene glycol (PEG), a commonly used hydrophilic polymer. Addition of a salt solution to PEG-coated AuNP solutions helps in screening the electrostatic repulsion between nanoparticles and generating a color change of the solutions from wine red to blue in 10 min in accordance with the MW of PEG, which illustrates the different stability degrees (SDs) of the AuNPs. The SDs are calculated by the absorbance ratios of the stable to the aggregated AuNPs in the solution. The root mean square end-to-end length (〈h²〉^1/2) of PEG molecules shows a linear fit to the SDs of the PEG-coated AuNPs in a range of 1.938 ± 0.156 to 10.151 ± 0.176 nm. According to the Derjaguin-Landau-Verwey-Overbeek theory, the reason for this linear relationship is that the thickness of the PEG adlayer is roughly equivalent to the 〈h²〉^1/2 of the PEG molecules in solution, which determines the SDs of the AuNPs. Subsequently, the MW of the PEG can be obtained from its 〈h²〉^1/2 using a mathematical relationship between 〈h²〉^1/2 and MW of PEG molecule. Applying this approach, we determined the 〈h²〉^1/2 and the MW of four PEG samples according to their absorbance values from the ordinary ultraviolet–visible spectrophotometric measurements. Therefore, the MW of PEG can be distinguished straightforwardly by visual inspection and determined by spectrophotometry. This novel approach is simple, rapid, and sensitive.     

Effects of orientation on mechanical properties of uniaxially oriented polystyrene films

Oriented samples of polystyrene have been produced by drawing at temperatures just above the glass transition range. Birefringence measurements have been used to characterise the degree of orientation. Mechanical measurements of elastic modulus and tensile yield stress have been made in the direction of drawing and it has been established that the birefringence value does not uniquely determine the mechanical properties—samples drawn to a high draw ratio at high temperatures have a higher modulus and yield stress than samples drawn at lower temperatures and lower draw-ratios to the same birefringence. The results are explained qualitatively by the convective constraint release theory of McLeish et al.     

A convenient method for the determination of molecular weight cut-off of ultrafiltration membranes

With the rapid increase of water contamination,membrane separation technology and their corresponding molecular weight cut-off (MWCO) evaluation method become more necessary.In this study,Panax notoginseng saponins was used as a new standard marker to determinate ultrafiltration (UF) membrane MWCOs,series of Millipore membranes were selected as control group to analyze and calculate the relationship between retention rate and MWCOs with exponential or logarithmic equation.A new and convenient method was provided for determining the membrane MWCO by modeling analysis retention rate with MWCOs,and the regression coefficients ≥0.990.The feasibility and practicability of established method was verified by different manufactures' membrane and dextrans.In the detection progress,as the main ingredient of Panax notoginseng saponins,Notoginsenoside R1,Ginsenoside Rg1,Ginsenoside Rb1and Ginsenoside Rd with different surface activity,the MWCO range of UF membranes can be divided into two zones mainly due to the retention rate difference among Notoginsenoside R1,Ginsenoside Rg1,Ginsenoside Rb1 and Ginsenoside Rd.Zone Ⅰ,1000-10000;and Zone Ⅱ,10000-100000.Thus,the new method would be helpful to improve the applicability of UF membrane in separation technology.     

The molecular weight distribution of oligomers

It is shown that the relation $\text{P}{}_{\mathrm{w}}\text{P}{}_{\mathrm{n}}\text{= 2}$ or the nonuniformity U = 1 is only a limiting case for high degrees of polymerization, is no more valid for oligomers. Two new relations are derived, one including and one excluding monomers. For the oligomer part of cationically produced polystyrenes the second relation is in good agreement with experiments.     

黄体酮纯度标准物质的研究

通过定性分析、定值分析、杂质分析、均匀性检验、稳定性考察和不确定度评定,研制了黄体酮纯度标准物质,并且成功申报成为国家标准物质(编号GBW100119).其中采用高效液相色谱法与差示扫描量热法对黄体酮纯度标准物质进行了定值分析.准确的定值结果为99.2%,相对扩展不确定度为0.5%.对于临床检验中黄体酮的准确测定及相关...     

3种定值方法用于维生素D3纯度标准物质的研究

通过定性分析、定值分析、均匀性检验、稳定性考察和不确定度评定,研制了维生素D3纯度标准物质。其中采用质量平衡法(包括液相色谱法、水分、灰分、挥发性物质和无机元素分析)、定量核磁共振法与差示扫描量热法3种不同原理的方法对维生素D3纯度标准物质进行了定值分析。准确的纯度定值结果为99.6%,扩展不确定度为0.6%。对于维生素D3的准确测定及相关疾病的正确诊断治疗具有重要意义。     

丁二烯橡胶门尼黏度标准物质的定值

对经过筛选、通过均匀性、稳定性检验后符合标准物质定值的丁二烯橡胶样品,采用多家实验室联合定值.并对各家实验室定值的结果按照标准物质定值数据处理程序,进行了异常数据判断、数据正态分布检验、等精度检验、不确定度评估.丁二烯橡胶门尼黏度标准物质定值各实验室的数据在a=O.05的显著水平时,数据无可疑值、处于正态分布、等精度,...     

水中硼环境标准样品的研究与制备

报导了水和废水环境监测用水质硼环境标准样品的研制情况。其中对水质硼环境标准样品的作用、样品的制备、均匀性测定、稳定性考察以及定值分析等方面做了较为详细的介绍。     

瓶级聚酯切片标准样品的研制

从标准物质的生产、均匀性和稳定性检验,标准物质的定值等方面介绍了瓶级聚酯切片标准样品研制过程。结果表明,新的瓶级聚酯切片标准样品均匀性、稳定性良好,定值数据准确可靠,能满足瓶级聚酯切片的测试要求。     

Analysis of ethoxylated fatty amines. Comparison of methods for the determination of molecular weight

Specific lengths of the fatty and polyoxyethylene chains of ethoxylated fatty amines are critical to their performance in specific applications, and thus the ability to characterize these surfactants accurately is crucial. Normal-phase high-performance liquid chromatography (HPLC) and matrixassisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry methods were developed to determine with accuracy the molecular weight and degree of ethoxylation of ethoxylated fatty amines. Ethoxylated fatty amines were analyzed using these methods, and comparison was made to molecular weight determinations using proton nuclear magnetic resonance (NMR), neutralization equivalent weight, and hydroxyl value methods. Molecular weight results from normalphase HPLC analyses were in very good agreement with MALDI-TOF results, typically varying less than one ethylene oxide unit. A reversed-phase HPLC method was developed to determine concentrations of polyethylene glycols (PEG) and fatty homologs. PEG interfered with molecular weight determinations by NMR, neutralization equivalent weight, and hydroxyl value methods. PEG caused no interference with molecular weight determinations by normal-phase HPLC and MALDI-TOF methods.     

Recovery of molecular weight distributions from transformed domains. Part II. Application of numerical inversion methods

This work is a part of a study aiming at developing tools for the prediction of complete molecular weight distributions (MWDs) of polymers at the exit of a reactor. This reactor may be a synthesis reactor or one used to modify a preexisting resin. In this work, we analyse the suitability of three methods for the numerical inversion of probability generating functions (pgfs), those due to Papoulis, de Hoog and Garbow. The three methods have been proposed in the literature for the inversion of Laplace transforms. We show how to adapt them to the problem at hand, and apply them to two situations. The first one is the recovery of experimentally measured MWDs, through a process that consists of finding the pgf of the distribution, numerically inverting it and comparing the result with the known MWD. The second one is to solve the pgf balances of polymerisation systems with known MWDs, and comparing those MWD with the ones that result from the inversion with the three methods. We discuss the relative advantages of each inversion method and propose guidelines for their proper use with unknown MWD functions.     

b型流感嗜血杆菌精制多糖分子大小分布及重均分子质量检测方法的改良

目的 改良HPLC(AKTA 层析)系统,采用HPLC-MALLS 系统检测b 型流感嗜血杆菌(Haemophilus influenzae type b,Hib)精制多糖的分子大小分布及重均分子质量(Mw),并进行方法的验证.方法 采用HPLC(AKTA层析)系统连接示差分析仪检测9批Hib精制多糖供试品的分配系数(...     

Molecular weight dependency of refractive index increment of polystyrene determined by uniform oligomers

Molecular weight dependency of a specific UV absorption coefficient of polystyrene in solution was determined by supercritical fluid chromatography applied to equimolar and equimass mixtures of uniform polystyrenes whose degree of polymerization was n = 1 to 40. From the ratio between the response from a UV detector and that from a refractometer, we determined the refractive index increment dn/dc as a function of molecular weight for polystyrene in tetrahydrofuran at the wavelength λ = 633 nm. We found that dn/dc is well expressed as a linear function of the reciprocal of molecular weight for uniform polystyrenes. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1101–1106, 2004     

Calculation of molecular weight distribution in styrene polymerization initiated by a binary initiator system

A computational scheme is presented for the calculation of molecular weight distribution in styrene polymerization initiated by a binary initiator system. In this paper, the method of finite molecular weight moment is presented by calculation of the polymer chain length distribution. This method is compared with the method of integrating an infinite number of polymer population balance equations. The results of the two methods show a reasonably good agreement. It is possible to produce polymer having the same molecular weight distribution.     

高效液相色谱法测定香菇多糖的分子量

本文建立了HPLC法测定香菇多糖的分子量的方法。采用GPC色谱柱,以醋酸盐缓冲溶液(0.2MpH值4.0)为流动相,示差折光检测器检测。结果表明:香菇多糖的分子量在3.9×104～8.0×105范围内具有良好的线性(r=0.99694)。测得样品分子量为7.1×105,精密度实验RSD为0.0983%。证明该法简便、快速、灵敏度高、重现性及稳定性均较好,可用于其它大分子量物质的分子量测定。     

Determination of molecular weight between crosslinks of coals from solvent-swelling studies

Solvent-induced swelling isotherms of coals and highly crosslinked porous polystyrene samples were measured by gravimetry and pycnometry. Comparison of solvent uptake by these two techniques corrects swelling values for occluded solvents. The high crosslink density and stiffness of chain segments preclude characterization of the macromolecular structure of these samples from swelling data, by the general Flory-Rehner equation. An alternative method tried was based on a rearrangement of the Flory-Rehner equation coupled with the Flory-Huggins equation. This method has been successful in estimating simultaneously the crosslink density and solvent-polymer interaction parameter of certain highly crosslinked polymers. It was hoped that swelling data corrected for uptake due to physical adsorption would yield at least semi-empirical information about the structure of coals. Unfortunately, while correcting the isotherms for solvent occluded in pores did improve the data, methanol swelling values were insufficient to characterize the present coal samples.     

Influence of molecular weight on the fracture properties of aliphatic polyketone terpolymers

The influence of polymer molecular weight on the mechanical properties of aliphatic polyketones was investigated. The molecular weight varied from 100,000 to 300,000 g mol⁻¹. The crystallinity was found to be independent of polymer molecular weight, as was the glass transition temperature. The yield strength and stiffness of the aliphatic polyketone terpolymers were also found to be independent of molecular weight. The post yield behaviour showed strong dependency on polymer chain length. The draw stress was increased significantly with higher molecular weight material. The impact resistance was increased with molecular weight, resulting in ductile fractures with large energy consumption upon fracture. The brittle-to-ductile transition temperature was lowered with increasing chain length. The difference in material deformation was linked to the higher mechanical connectivity and more stable post yield behaviour of the polymers with an increased molecular weight.     

Do molecular weight determinations of coal-derived materials give meaningful answers?

The relation between number-average (M?_n) and weight-average (M?_w) molecular weights has been examined, and it was demonstrated how this can be employed to determine the self-consistency of results obtained for calculating molecular weights of chemically treated coals. The present method of calculation was calibrated against data of Katz et al., then applied to the data of Sun and Burk for g.p.c. fractions of alkylated coals. The newly calculated value for M?_w (3300) did not agree with Sun and Burk's value of 7882.     

Analysis of ultracentrifugation interference patterns with image digitizer: Application to molecular weight determination of SRM 1478 polystyrene

A new method for the analysis of ultracentrifugation interference patterns with the use of a commercial image digitizer is given. The application of the method to the sedimentation equilibrium data for SRM 1478 polystyrene leads to a weight-average molecular weight of 37 400 g mol⁻¹ having a sample standard deviation of 0.7% and an expected systematic error limit of 2%.