Thermal stability of model compounds related to thermostable polymers by pyrolysis-gas chromatography

Thermal stabilities of eighteen model compounds related structurally to thermostable polymer systems were determined accurately by pyrolysis-gas chromatography. This approach offers distinct advantages over previously used indirect methods which measure parameters other than actual starting material remaining undecomposed. Both the oxadiazole ring and the aromatic amide link were found to have poor thermal stabilities in comparison with other compounds studied. Since polymers based on these two features have been shown to be valuable for use in air at 200–400°C., the data suggest that oxidation resistance rather than the ultimate in pure thermal resistance should be sought in all-purpose thermostable materials.     

PY-GC法研究渣油中硫化物的热裂解性能

采用裂解气相色谱（PY-GC）方法研究渣油中的大分子硫化物的裂解性能。首先对（PY-GC）的实验条件进行优化,在此基础上,得到了可以反应渣油样品中硫化物组成和结构的裂解色谱图;通过标准物对比并结合文献对渣油裂解产物中硫化物的组成进行定性。研究发现,渣油高温裂解产物中的硫化物主要有：H2S、噻吩类、苯并噻吩类和二苯并噻吩类系列的化合物。根据模型化合物的裂解色谱分析结果,推测出渣油裂解产物中的H2S不仅来源于重油分子中硫醚类结构的裂解,而且与重油分子中噻吩、苯并噻吩和二苯并噻吩类结构的裂解有关,而渣油裂解产物中的噻吩、BT和DBT系列化合物主要来自于重油中的大分子噻吩、BT和DBT类化合物的裂解。     

Comparison of analyses of surfactants in cosmetics using high-performance liquid chromatography and high-performance capillary electrophoresis

Separation of anionic, cationic, and amphoteric surfactants containing n-dodecyl groups and hydrophilic moieties was done by high-performance liquid chromatography (HPLC) and high-performance capillary electrophoresis (HPCE), and an ultraviolet-visible detector. Quantitation of surfactants in commercial cosmetic and toiletry products was also done using similar methods. Conditions used to separate mixtures of surfactants by HPLC are as follows: stationary phase: ODS 2; mobile phase: MeOH/H₂O (80∶20, vol/vol) containing 1.0M NH₄Cl, 0.003 M tetrabutylammonium hydrogen sulfate, and 0.005 M diammonium phosphate buffer solution at pH=6.0. Conditions for HPCE are as follows: an uncoated capillary (100 μm i.d., 110 cm in length, effective length of 75 cm) with 25 kV of applied voltage, and an aqueous buffer containing 80 mM sodium borate/20 mM NaOH at pH=9.2. Surfactants were eluted within 15 min. The accuracy of both techniques was evaluated by analyzing the recovery ratio of surfactants in the mixture.     

Studies on thermal degradation behaviour of anionically copolymerized styrene-divinylbenzene copolymers by high-resolution pyrolysis-gas chromatography

Anionically and radically copolymerized styrene-divinylbenzene copolymers with comparable divinylbenzene contents have been synthesized and studied by high-resolution pyrolysis-gas chromatography. The considerable differences in thermal degradation behaviour observed between both copolymer systems were interpreted on the basis of differences in the expected network structures for the corresponding copolymer systems. In addition, thermogravimetric analysis was carried out to evaluate the thermal degradation behaviour of the copolymers.     

Identification of polyoxyalkylene-type nonionic surfactants by paper chromatography

Despite the increasing importance of nonionic surfactants, methods for their identification have been limited to specific groups. Accordingly, a general analytical scheme for the identification of polyoxyalkylene-type nonionic surfactants was developed, which uses qualitative tests and two paper chromatographic solvent systems. This procedure differentiates among the ethoxylates of alcohols, thioalcohols, alkyl phenol, fatty acids, polyoxyethylene polyoxypropylene acids, sorbitan fatty esters, fatty amides, polyoxyethylene glycols (PEG) condensates. In addition, individual members of a class can be separated and identified. The method is applicable to a variety of detergent products and to mixtures of more than one nonionic. As little as 7 mg of a nonionic surfactant are sufficient for complete characterization. Presented at the AOCS Meeting, Washington, D.C., April, 1968.     

Characterization of nonionic surfactants using supercritical fluid chromatography and carbon-13 nuclear magnetic resonance spectroscopy

Capillary supercritical fluid chromatography, using a carbon dioxide mobile phase and flame ionization detection, was employed for characterization of nonionic alcohol ethoxylate surfactants. Data from separations was used to calculate average molecular weights, degree of ethoxylation and distribution of telomers. The SFC approach was compared with carbon-13 nuclear magnetic resonance spectroscopy for evaluation of the same samples. The faster chromatographic technique permitted information to be obtained in the presence of materials which interfered with the NMR analysis, and provided a means of identifying the minor components of mixtures. The advantages and disadvantages of the methods are discussed and the complementary nature of the techniques illustrated.     

Analysis of anions in beer using ion chromatography

The majority of anions found in beer are a consequence of impurities derived from the water used during the brewing process. The process of beer manufacture consists of malting, brewing and fermentation followed by maturation before filtration and finally storage. Strict quality control is required because the presence of certain anions outside strictly defined tolerance limits can affect the flavour characteristics of the finished product. The anions present were quantified using the technique of ion chromatography with the Metrohm modular system following sample preparation. The analysis produced a result of the order 200 mg l(-1) for chloride, phosphate and sulphate and around 20 mg l(-1) for nitrate. If the chloride level exceeds 250 mg l(-1), then the sweetness of the beer is enhanced, but yeast flocculation can be hindered. An excess of sulphate can give a sharp, dry edge to hopped beers and excessive amounts of nitrate have been found to harm the yeast metabolism after conversion to the nitrite form. As water is a primary ingredient within beer, its quality and type is a fundamental factor in establishing many of the distinctive regional beers that can be found in the United Kingdom and is thus monitored carefully.     

Analysis of surfactants adsorbed on cement using secondary ion mass spectrometry (SIMS)

The SIMS-technique permits both the qualitative and the quantitative analysis of surfactants adsorbed on cement or its hydration products. The principles of such an analysis are discussed and some typical results are presented.     

Analysis of surfactants: Part II

We present a comprehensive review of the literature devoted to the analysis of surfactants. The period covered is 1995 through 1998. We address patents, reviews, books, journal articles, and any conference proceedings abstracted by Chemical Abstract Services. We consider classical, instrumental, and state-of-the-art analytical applications, including those not in common practice but in a developmental stage. We also include analytical techniques that make use of surfactants for improved performance, although such treatment is not comprehensive. Literature from foreign language sources is covered as completely as practical.     

Analysis of surfactants: Part I

We present a comprehensive review of the literature devoted to the analysis of surfactants. The period covered is 1995 through 1998. We address patents, reviews, books, journal articles, and any conference proceedings abstracted by Chemical Abstract Services. We consider classical, instrumental, and state-of-the-art analytical applications, including those not in common practice but in a developmental stage. We also include analytical techniques that make use of surfactants for improved performance, although such treatment is not comprehensive. Literature from foreign language sources is covered as completely as practical.     

高效液相色谱法分析间二甲苯氧化过程的产物

采用高效液相色谱,外标法定量测定间二甲苯氧化制间苯二甲酸生产过程中的各种物质的含量:间甲基苯甲醛(m PA)、间甲基苯甲酸(m PT)、间羧基苯甲醛(3 CBA)、间苯二甲酸(IPA)和间二甲苯。采用C18柱,磷酸二氢钾水溶液和乙腈双流动相梯度淋洗和变波长紫外监测,可通过一次进样在30min内完成对该氧化体系的5种主要物质的全面分析。     

Solubilisation of water in alkanes using nonionic surfactants

Nonionic surfactants are frequently used as emulsifiers in nonpolar oil + water systems and as solubilisation agents for oil in water, or vice versa. In the latter application the amount of, say, water that can be solubilised in nonpolar oil (to give microemulsion droplets) depends on: (a) the capacity of the micelles to incorporate water; and (b) the fraction of surfactant originally present as micelles. This paper is concerned with the single-phase water-in-oil (W/O) microemulsion regions enclosed by the haze and solubilisation boundaries at the oil-rich end of Shinoda-type phase diagrams. The systems studied contain the nonionic surfactant C₁₂H₂₅(OCH₂CH₂)₅OH (C₁₂E₅), normal alkane (heptane, decane or tetradecane) and water. Critical microemulsion concentrations (cμc) and droplet compositions for w/o microemulsions formed from C₁₂E₅ in alkane have been determined at phase boundaries over a range of temperatures. The results show how the maximum extent of water solubilisation is determined jointly by the cμc and the maximum droplet size for a given temperature. It appears that for larger (microemulsion) droplets, the cμc is determined by temperature rather than by droplet size. However, along part of the haze curves, aggregates form with only small amounts of water (less than four molecules per ethyleneoxy group on the surfactant head groups). For a given temperature, in the small range where either micelles or microemulsion droplets can exist, reverse hydrated micelles have much higher critical micelle concentrations (cmc) than the cμc of the larger microemulsion droplets.     

表面活性剂复配体系修复芘污染土壤实验

以芘污染土壤为对象,利用阴离子表面活性剂鼠李糖脂和非离子表面活性剂皂素进行复配实验,得出最佳复配比并对污染土壤进行修复处理;其次,研究表面活性剂浓度、pH及CaCl₂、MgCl₂、KCl三种离子浓度、洗脱液的回收次数等单因素对洗脱效果的影响;然后利用响应曲面分析,确定影响洗脱效果的主效应因素及其交互作用强度;最后用Box-Behnken模型优化复配体系处理芘污染土壤的实验条件。结果表明：①当复配比为0.2时,鼠李糖脂-皂素混合溶液的表面张力最低,对芘的协同增溶效果最好;②复配体系处理芘污染土壤的单因素实验中,复配药剂浓度、pH、Mg²⁺浓度分别达到1800mg/L、8、0.1mmol/L时,洗脱效率最高;③环境因素对芘去除效果的影响从大到小依次为pH>表面活性剂浓度>Mg²⁺浓度,表面活性剂浓度与pH对芘的洗脱产生较大的交互影响作用,而pH与盐浓度的交互作用最微弱;④Box-Behnken模型优化后得出最佳组合是混合表面活性剂浓度为1900mg/L、pH为5、Mg²⁺浓度为0.2mmol/L,得到的洗脱效率为89.25%。     

Optimization of experimental parameters for separation of nonionic surfactants by supercritical fluid chromatography

A synthetic polymer generally consists of a mixture of many compounds that share the same repeating unit but have different degrees of polymerization. Because of its ability to cope with a wide range of molecular weights, supercritical fluid chromatography (SFC) is a powerful technique for separating the individual components of polymers. However, the separation conditions for SFC are more sensitive than those of other types of chromatography, and many experimental parameters need to be carefully selected to achieve high resolutions. Methods for optimizing the experimental parameters for SFC of a polymeric surfactant were investigated by chemometric techniques. Increases or decreases in peak resolution and elution times were measured for the separation by SFC of the nonionic surfactant poly(ethylene glycol) nonylphenyl ether for various column temperatures, flow-rate gradients of modifier, and modifier compositions. To maximize the separation efficiency, the experimental results were analyzed by using the chromatographic response function (CRF). This is a function of the desired peak resolution, the maximum acceptable elution time, and an arbitrary weighting factor that is adjusted to achieve an optimal balance between the peak separation and the elution time. Because the numerical value of the CRF changes in response to the chromatographic performance, it provides a means of identifying the conditions for achieving optimal separation for a particular SFC system.     

Quantitative determination of polyethylene glycols in nonionic surfactants by high pressure liquid chromatography

A method employing high pressure liquid chromatography has been developed for the quantitative determination of polyethylene glycols in ethoxylated fatty alcohols and alkylphenols. This technique overcomes many of the limitations encountered in previously-reported methods. The polyethylene glycols are separated from the ethoxylated product and other sample components using a 65/35 acetonitrile/water mobile phase and a Bondapak C₁₈/Corasil reversephase column system. The response factor of the differential refractometer detector is determined using Carbowax standards of appropriate molecular weights. The molecular weight of the polyethylene glycols in each sample is approximated using thin layer chromatography prior to the high pressure liquid chromatography calibration and analysis. The precision of this method for the determination of polyethylene glycols is ± 4% relative or better, and the recovery of added polyethylene glycols is quantitative. Application of this method to a wide variety of commercial ethoxylated fatty alcohols and alkylphenols is presented. Presented at the Meeting of the American Oil Chemists’ Society, April 1976, New Orleans.     

Analysis of exempt paint solvents by gas chromatography using solid-phase microextraction

Acetone, methyl acetate, and parachlorobenzotrifluoride (PCBTF or Oxsol? 100) have been exempted as VOC solvents by the U.S. Environmental Protection Agency. In measuring coating VOC content, separate methods for determining exempt solvents are required. One such method utilizes solid-phase microextraction (SPME) to sample the headspace of solvent-based coatings to which the surrogates acetone-d6, methyl acetate-d3, and/or metachlorobenzotrifluoride have been added. The sampled exempt coating solvents are thermally desorbed and analyzed using gas chromatography with flame ionization or mass spectral detection. The SPME headspace method has also been used to analyze MEK, butyl acetate, tert-butyl acetate, toluene, and xylene in solventborne coatings, and alcohols in waterborne systems. This paper presents the results obtained for acetone and toluene in a large number of aerosol paints. Additionally, the results from a round-robin study for acetone, methyl acetate, and parachlorobenzotrifluoride in commercial solvent-based coatings are reported.     

Formulation of ultralow interfacial tension systems using extended surfactants

Inspired by the concept of lipophilic and hydrophilic linkers, extended surfactants have been proposed as highly desirable candidates for the formulation of microemulsions with high solubilization capacity and ultralow interfacial tension (IFT), especially for triglyceride oils. The defining characteristic of an extended surfactant is the presence of one or more intermediate-polarity groups between the hydrophilic head and the hydrophobic tail. Currently only limited information exists on extended surfactants; such knowledge is especially relevant for cleaning and separation applications where the cost of the surfactant and environmental regulations prohibit the use of concentrated surfactant solutions. In this work, we examine surfactant formulations for a wide range of oils using dilute solutions of the extended surfactant classes sodium alkyl polypropyleneoxide sulfate (R-(PO) _x −SO₄Na), and sodium alkyl polypropyleneoxide-polyethyleneoxide sulfate (R-(PO) _y -(EO) _z −SO₄Na). The IFT of these systems was measured as a function of electrolyte and surfactant concentration for polar and nonpolar oils. The results show that these extended surfactant systems have low critical micelle concentrations (CMC) and critical microemulsion concentrations (CμC) compared with other surfactants. We also found that the unique structure of these extended surfactants allows them to achieve ultralow IFT with a wide range of oils, including highly hydrophobic oils (e.g., hexadecane), triolein, and vegetable oils, using only ppm levels of these extended surfactants. It was also found that the introduction of additional PO and EO groups in the extended surfactant yielded lower IFT and lower optimum salinity, both of which are desirable in most formulations. Based on the optimum formulation conditions, it was found that the triolein sample used in these experiments behaved as a very polar oil, and all other vegetable oils displayed very hydrophobic behavior. This unexpected triolein behavior is suspected to be due to uncharacterized impurities in the triolein sample, and will be further evaluated in future research.     

Liquid chromatography-mass spectrometry of nonionic surfactants using electrospray ionization

The analysis of nonionic surfactants was investigated by reversed-phase liquid chromatography with mass spectrometry detection. On a C₁₈ column, separation was achieved on the basis of chain lengths of both alkyl and ethoxy groups in a CH₃CN/CH₃OH/H₂O/HAc solvent system. Peaks were identified by electrospray mass spectrometry.     

Analysis of cationic and amphoteric surfactants: III. Structural analysis of imidazolinium cationic surfactants

Determination of the homologous distribution of imidazolinium cationic surfactants and their structural analysis have been inves-tigated. These surfactants were hydrolyzed under aqueous alkaline media, followed by acid hydrolysis to afford fatty acids and poly-amines. The resulting fatty acids were esterified with methanol, and then analyzed by gas chromatography (GC) in order to determine their homologous distribution. The obtained distribution agrees well with that of original fatty acid. Therefore, this method should be applicable to the determination of the homologous distribution of imidazolinium surfactants. The resulting polyamines were acetylated with acetic anhydride in the presence of pyridine. These acetates were analyzed by GC and isolated by preparative thin layer chroma-tography on silica gel. The structures of these isolates were identi-fied by means of 1 H-NMR and 1R spectrometry. These structural analyses demonstrated that quaternization of an imidazoline ring selectively occurred at the nitrogen at the 3-position of an imida-zoline ring, which was the kinetically favored position in terms of the steric hinderence and the stability of product.