反气相色谱法与Hansen溶解度参数法测定聚乙烯醇溶解度参数及相关热力学性质

采用反气相色谱（IGC）法,以聚乙烯醇（PVA）为固定相,脂肪族、芳香族、醇、酮及卤代烃5类18种化合物为探针分子,研究PVA的溶解性质并获得了PVA在383.15～423.15 K范围内的溶解度参数（δ₂）及相关热力学性质,并与Hansen溶解度参数法（HSP）测得的溶解度参数（δ_T）进行比较。结果表明,5类溶剂对PVA溶解能力的趋势为酮类 >醇类 >卤代烃、芳香类、脂肪族类>脂环族,卤代烃、芳香类和脂肪族类溶剂的溶解能力相似;在测试温度范围内PVA的δ₂随温度升高而增加;采用IGC法外推出室温（298.15 K）下PVA的δ₂为27.69 （J/cm³）^0.5,与HSP法测得室温下PVA的δ_T（27.77 （J/cm³）^0.5）一致。PVA溶解度参数及相关热力学参数的研究为其应用及相关研究提供了定量依据。     

Surface thermodynamics of Efavirenz and a blend of Efavirenz with cellulose acetate propionate by inverse gas chromatography

The purpose of this paper is to study the effect of an excipient on the surface energetics of Efavirenz (EFV) drug. The net retention volumes, V_N, for n‐alkanes and polar solutes on the two columns, namely, EFV drug and a blend of EFV with cellulose acetate propionate have been measured by inverse gas chromatography. The dispersive surface free energy, , Lewis acid parameter, K_a, and Lewis base parameter, K_b, have been determined using V_N values. The values are decreased linearly with increase of temperature for pure EFV as well as for the blend. Furthermore, the values of EFV are higher than in the blend, for example, values at T = 318.15 K for EFV, and for the blend are 28.09 ± 6.02 mJ/m² and 28.30 ± 2.31 mJ/m², respectively. The specific component of surface free energy has been obtained by the Schultz method as well as by the Dong et al. method. The values have been used to calculate Lewis acid‐base parameters for the EFV as well as the blend. The K_a values for the EFV and the blend are almost similar, where as the K_b values are higher in EFV than in the blend. Similar trend in K_a and K_b has been observed in both methods studied. Copyright © 2015 John Wiley & Sons, Ltd.     

反相气相色谱法研究1,3,5-三氨基-2,4,6-三硝基苯的表面特性

采用反相气相色谱技术(IGC)研究了4种不同粒度的1,3,5-三氨基-2,4,6-三硝基苯(TATB)的表面性质。4种不同粒度的TATB表面自由能的色散分量（γds）随着温度的升高而增加;粒度越大的粒子,其色散自由能上升越快;在较高温度下,粗颗粒TATB显示了更强的色散作用(γds=193.2 mJ/m2,353 K),粒度最小的亚微米TATB显示了最弱的色散作用(γds=64.0 mJ/m2,353 K)。由于制备方法不同和粒子大小的差异,4种TATB的表面酸碱性质显示了明显的差别,细颗粒TATB表面有较强的亲电子特性;而其他3种TATB在极性探针分子的作用下的吸附均表现为吸热吸附,表现出在分子内和分子间具有强烈的相互作用,其Ka和Kb值均为负。     

聚氯乙烯-聚氧乙烯共混物的反相色谱研究

用反相色谱研究了聚氯乙烯与聚氧乙烯的相容性,发现其共混物的比保留体积V_g23具有重量加和性,表明共混物可能发生了相分离。导出了相分离体系聚合物相互作用参数X₂₃的近似关系式:X₂₃=(X₁₂-X₁₃)²/2,由此式可以解释X₂₃对探针种类的依赖性。聚氯乙烯和聚氧乙烯共混体系的反相色谱实验结果基本符合这一关系式。     

反气相色谱法测定苯乙烯-氧乙烯-苯乙烯三嵌段聚合物的表面能

 采用反气相色谱法测定了苯乙烯 氧乙烯 苯乙烯三嵌段聚合物 (PS PEO PS)的色散成分的表面能 (γsd) ,研究探讨了温度及嵌段聚合物链段结构组成对γsd 的影响 ,并确定了γsd 与温度的数学关系式。研究结果表明 :在 70℃～ 12 0℃范围内 ,PS PEO PS的表面能较低 ;随着PS PEO PS表面组成中氧乙烯 (EO)成分的增加 ,色散成分的γsd 增大 ,且对温度的变化极其敏感 :随温度的升高 ,γsd 急剧地呈线性下降。     

苯乙烯-氧乙烯-苯乙烯三嵌段聚合物的受限结晶行为的反气相分析

 采用反气相法研究了苯乙烯 氧乙烯 苯乙烯三嵌段结晶聚合物 (PS PEO PS)的结晶熔融相变 ,测定了PS PEO PS的结晶度、熔点以及熔程 ,探讨了正构烷烃探针分子的碳链长度对测定结果的影响。研究结果表明 :PS PEO PS的微相分离对PEO链段的结晶行为有较大的影响 ,其晶体结构中存在由多种不完善PEO结晶和PS非结晶构成的中间层 ;正构烷烃探针分子的碳链长度对测定PS PEO PS的熔点和熔程无影响 ,但对结晶度测定和PEO结晶熔融相变的检测影响较大 ,所测得PS PEO PS的结晶度随正构烷烃探针分子碳链的增长而降低。     

Surface modification of high-performance polymeric fibers by an oxygen plasma. A comparative study of poly(p-phenylene terephthalamide) and poly(p-phenylene benzobisoxazole)

Poly(p-phenylene terephthalamide) (PPTA) and poly(p-phenylene benzobisoxazole) (PBO) fibers were exposed to an oxygen plasma under equivalent conditions. The resulting changes in the surface properties of PPTA and PBO were comparatively investigated using inverse gas chromatography (IGC) and atomic force microscopy (AFM). Both non-polar (n-alkanes) and polar probes of different acid-base characteristics were used in IGC adsorption experiments. Following plasma exposure, size-exclusion phenomena, probably associated to the formation of pores (nanoroughness), were detected with the largest n-alkanes (C(9) and C(10)). From the adsorption of polar probes, an increase in the number or strength of the acidic and basic sites present at the fiber surfaces following plasma treatment was detected. The effects of the oxygen plasma treatments were similar for PPTA and PBO. In both cases, oxygen plasma introduces polar groups onto the surfaces, involving an increase in the degree of surface nanoroughness. AFM measurements evidenced substantial changes in the surface morphology at the nanometer scale, especially after plasma exposure for a long time. For the PBO fibers, the outermost layer - contaminant substances - was removed thanks to the plasma treatment, which indicates that this agent had a surface cleaning effect.     

气相色谱法测定羟乙基乙二胺中的乙二胺含量

采用毛细管气相色谱内标法测定羟乙基乙二胺中的乙二胺含量．结果表明。乙二胺在0．12．0ms／mL范围内的线性关系良好（r=0．9997）,检出限为0．02m/mL,方法的精密度RSD为1．7％（n=6）,加标回收率在95％～101％．     

水田除草剂2-(2-萘氧基)丙酰替苯胺的气相色谱法测定

在５ ％ ＯＶ７／Ｃｈｒｏｍｏｓｏｒｂ ＷＡＷ ＤＭＣＳ的色谱柱上分离和测定水田除草剂２（２萘氧基） 丙酰替苯胺（ 俗称萘丙胺） 。以苯二甲酸二异辛酯为内标物时,萘丙胺与内标物等之间均获得较好的分离。而且,萘丙胺的相对质量校正因子相当稳定,ｆＷ．Ａ＝０ ．９７８ ±０．００５（α＝ ０．０５,ｎ＝ ６） 。该方法具有操作简便、快速、准确度和精密度较好,对同一试样的多次平行独立测定其标准偏差≤０．９０,变异系数≤１ ．１８ ％ 。该方法完全适合于水田除草剂萘丙胺的生产控制分析和产品质量的检验。     

气相色谱法测定1-(5-溴-1H-吲唑-1-基)乙酮

建立了测定1-(5-溴-1H-吲唑-1-基)乙酮纯度的气相色谱法。采用DB–5型色谱柱,程序升温,火焰光度检测器,外标法定量,1-(5-溴-1H-吲唑-1-基)乙酮在100~1 000 mg/L范围内内线性关系良好,检出限为0.01mg/L。测定结果的相对标准偏差为1.67%~1.89%(n=5),样品加标回收率为98.1%~107.9%。用该方法测定了自制的1-(5-溴-1H-吲唑-1-基)乙酮样品的纯度。该测定方法准确度高、专属性较强且灵敏度较高,适用于1-(5-溴-1H-吲唑-1-基)乙酮的质量控制。     

Interaction and Scale of Mixing in Cellulose Acetate/Poly(<Emphasis Type="Italic">N</Emphasis>-vinyl Pyrrolidone-co-vinyl Acetate) Blends

Binary blends and pseudo complexes of cellulose acetate (CA) with vinyl polymers containing N-vinyl pyrrolidone (VP) units, poly(N-vinyl pyrrolidone) (PVP) and poly(N-vinyl pyrrolidone-co-vinyl acetate) [P(VP-co-VAc)], were prepared, respectively, by casting from mixed polymer solutions in N,N-dimethylformamide as good solvent and by spontaneous co-precipitation from solutions in tetrahydrofuran as comparatively poor solvent. The scale of miscibility and intermolecular interaction were examined for the blends and complexes by solid-state ¹³C-NMR spectroscopy. It was revealed that the formation of complexes was due to a higher frequency of hydrogen-bonding interactions between the residual hydroxyl groups of CA and the carbonyl groups of VP residues in the vinyl polymer component. From measurements of CP/MAS spectra and proton spin-lattice relaxation times (T_1ρ^H) in the NMR study, the existence of the hydrogen-bonding interaction was also confirmed for the miscible blends and the homogeneity of the mixing was estimated to be substantially on a scale within a few nanometers.     

Characterization of the Chemical Profile of Euphorbia Species from Turkey by Gas Chromatography–Mass Spectrometry (GC-MS), Liquid Chromatography–Tandem Mass Spectrometry (LC-MS/MS), and Liquid Chromatography–Ion Trap–Time-of-Flight–Mass Spectrometry (LC-IT-TOF-MS) and Chemometric Analysis†

The Euphorbiaceae family comprises of about 300 genera and 5000 species primarily distributed in America and tropical Africa. The Euphorbia genus is represented by 105 species and locally named as “Sütle?en” and “Xa?îl” in Turkey. The present study aimed to determine the chemical constituents of E. aleppica, E. eriophora, E. macroclada, E. grisophylla, E. seguieriana subsp. seguieriana, E. craspedia, E. denticulata, E. falcata, and E. fistulosa, and classify them by utilizing the chemometric techniques of principal component analysis (PCA) and hierarchical cluster analysis (HCA). Linoleic acid, 17-tetratriacontane, palmitic acid, and hexatriacontane were the major fatty acids from the gas chromatography–mass spectrometry (GC/MS) analyses. Characterization of 268 constituents of the studied species was achieved by liquid chromatography–ion trap–time-of-flight–mass spectrometry (LC-IT-TOF-MS). Furthermore, a new liquid chromatography–tandem mass spectrometry (LC-MS/MS) method was developed and validated for the simultaneous quantitative determination of 11 compounds (quinic acid, protocatechuic acid, rutin, hesperidin, eugenol, p-coumaric acid, piceatannol, scopoletin, dl-kavain, chrysophanic acid, and resiniferatoxin) in these species. The developed method was validated for the linearity, limit of detection, limit of quantification, repeatability, and recovery.     

Miscibility and surface characterization of a poly(vinylidene fluoride)‐poly(vinyl methyl ketone) blend by inverse gas chromatography

The miscibility of blends of semicrystalline poly(vinylidene fluoride)(PVF₂) and poly(vinyl methyl ketone) (PVMK) along with surface characterization were investigated using the inverse gas chromatography method (IGC), over a range of blend compositions and temperatures. Three chemically different families, alkanes, acetates, and alcohols, were utilized for this study. The values of the PVF₂‐PVMK interaction parameters were found to be slightly positive for most of the solutes used, although some degree of miscibility was found at all compositions. Miscibility was greatest at a 50:50 w/w composition of the blend. The interaction parameters obtained from IGC are in excellent agreement with those obtained using calorimetry on the same blends. The calculated molar heat of sorption of alkanes, acetates, and alcohols into the blend layer reveal the impact of the combination of dispersive and hydrogen bonding forces on the interaction of solutes with the blend's backbone. The dispersive component of the surface energy was found to range from 18.70–64.30 mJ/m² in the temperature range of 82–163 °C. A comparison of the blend's surface energy with that of mercury and other polymers is given. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1155–1166, 2000     

Method development for compositional analysis of low molecular weight poly(vinyl acetate) by matrix-assisted/laser desorption-mass spectrometry and its application to analysis of chewing gum

The influence of the sample preparation parameters (the choice of the solvent and of the matrix:analyte ratio) was investigated and optimal conditions were established for MALDI mass spectrometry analysis of the pristine low molecular weight polyvinyl acetate (PVAc). It was demonstrated that comparison of polymer’s and solvent’s Hansen solubility parameters could be used as a guide when choosing the solvent for MALDI sample preparation. The highest intensity PVAc signals were obtained when ethyl acetate was used as a solvent along with the lowest matrix–analyte ratio (2,5-dihydroxybenzoic acid was used as a matrix in all experiments). The structure of the PVAc was established with high accuracy using the matrix-assisted laser desorption/ionization-Fourier transform mass spectrometry (MALDI-FTMS) analysis. It was demonstrated that PVAc undergoes unimolecular decomposition by losing acetic acid molecules from its backbone under the conditions of FTMS measurements. Number and weight average molecular weights as well as polydispersity indices were determined with both MALDI-TOF and MALDI-FTMS methods. The sample preparation protocol developed was applied to the analysis of a chewing gum and the molecular weight and structure of the polyvinyl acetate present in the sample were established. Thus, it was shown that optimized MALDI mass spectrometry could be used successfully for characterization of polyvinyl acetate in commercially available chewing gum.     

Synthesis and characterization of amphiphilic poly(N‐vinyl pyrrolidone)‐b‐poly(ε‐caprolactone) copolymers by a combination of cobalt‐mediated radical polymerization and ring‐opening polymerization

An amphiphilic block copolymer of poly(N‐vinyl pyrrolidone)‐b‐poly(ε‐caprolactone) (PVP‐b‐PCL) was synthesized by a combination of cobalt‐mediated radical polymerization (CMRP) and ring‐opening polymerization (ROP). The micellar characteristics of this copolymer were subsequently investigated. PVP (M_n = 11,400, M_w/M_n = 1.32) was synthesized at 20 °C via CMRP using a molar ratio of [VP]₀/[V‐70]₀/[Co]₀ = 150/8/1. The PVP was then reacted with 2,2′‐azobis[2‐methyl‐N‐(2‐hydroxyethyl)propionamide] (VA‐086) to modify its cobalt complex chain end to a hydroxyl group. The cobalt (Co) content in the resulting PVP‐OH was 1.2 ppm, indicating that all of the covalent Co? C bonds were cleaved and reacted with VA‐086, and that the separated cobalt complexes were successfully removed. The ROP of CL was subsequently carried out using the produced PVP‐OH as a macroinitiator at 110 °C. The GPC trace of PVP‐b‐PCL was monomodal without any tailing caused by the residual PVP‐OH, indicating that the initiation efficiency was very high. The critical micelle concentration (CMC) of PVP‐b‐PCL (M_n = 18,000, M_w/M_n = 1.35) was 0.015 mg/mL. The PVP‐b‐PCL micelles were spherical in shape with an average diameter of 105 nm. The nanosized PVP‐b‐PCL micelles show promise as novel drug carriers in biomedical and pharmaceutical applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3078–3085, 2009     

Detection of microphase separation in poly(tert-butyl acrylate-b-methyl methacrylate) synthesized via atom transfer radical polymerization by inverse gas chromatography

A trace amount of solvents such as n-octane, n-nonane, n-decane, ethyl acetate, n-propyl acetate, isoamyl acetate, toluene, ethyl benzene, n-propyl benzene, isopropyl benzene and chloro benzene was passed through the column of a gas chromatograph of which the stationary phase is poly(tert-butyl acrylate-b-methyl methacrylate), poly(tBA-b-MMA), block copolymer with low polydispersity, prepared via ATRP of tBA and MMA, respectively. The retention diagrams to determine the thermal transition of the polymer were obtained by plotting the logarithm of the specific retention volumes of isoamyl acetate and toluene against reciprocal values of absolute column temperatures between 40 and 170 °C by inverse gas chromatography (IGC) technique. Three glass transition temperatures, T_gs of poly(tBA-b-MMA) were determined at 50, 70 and 105 °C by IGC indicating the phase separation of the polymeric blocks in the copolymer. The thermodynamical interaction parameters such as weight fraction activity coefficient of solvent at infinite dilution, , Flory-Huggins polymer-solvent interaction parameter, , equation-of-state polymer solvent interaction parameter, , effective exchange energy parameter, X_eff, and solubility parameter of the copolymer, δ₂ were calculated at studied temperatures. The closeness of parameters of the poly(tBA-b-MMA) to those of the PMMA indicated that the continuous phase is MMA block in the microphase separated block copolymer. It seems that IGC is a reliable technique to study a phase separated block copolymer which contains nanosized domains.     

Enantiomeric Enrichments via the Self‐Disproportionation of Enantiomers (SDE) by Achiral,Gravity‐Driven Column Chromatography: a Case Study Using N‐(1‐Phenylethyl)acetamide for Optimizing the Enantiomerically Pure Yield and Magnitude of the SDE

This work explores the self‐disproportionation of enantiomers (SDE) via achiral, gravity‐driven column chromatography as typically used in laboratory settings for the purpose of enantiomeric enrichment using N‐(1‐phenylethyl)acetamide (PEA) as a case study. The major finding of this work is the very large magnitude of the SDE for PEA across a variety of conditions and broad range of starting ee values, thereby facilitating a simple, reliable, and predictable means of obtaining enantiomerically pure samples. For example, starting with a sample of PEA of ee as low as 28%, a single column run yielded an enantiomerically pure sample (>99.9% ee) from the first fractions and a significantly enantiomerically depleted sample (<17% ee) from the final fractions. An assessment of SDE via achiral, gravity‐driven column chromatography was also rendered with regard to the differing objectives that workers might target – a large magnitude of the SDE, obtaining an optimum sample of desired ee, or preparative‐scale separation of the excess enantiomer. Overall, it can be considered that the SDE phenomenon via achiral, gravity‐driven column chromatography – readily applicable in the usual laboratory settings – is a simple and convenient method for enantiomeric enrichment with a high degree of proficiency. Advantages of SDE via achiral, gravity‐driven column chromatography over conventional fractional recrystallization for the enantiomeric enrichment of amides/amines, and applicable also to many other classes of compounds as well, are discussed.