Surface energy characteristics of toner particles by automated inverse gas chromatography

This study develops a method for the analysis of biocides Irgarol 1051 and Sea Nine 211 in environmental water samples, using solid-phase microextraction (SPME). Their determination was carried out using gas chromatography with flame thermionic (FTD), electron-capture (ECD) and mass spectrometric detection. The main parameters affecting the SPME process such as adsorption-time profile, salt additives and memory effect were studied for five polymeric coatings commercially available for solid-phase microextraction: poly(dimethylsiloxane) (100 and 30 microm), polyacrylate, poly(dimethylsiloxane)-divinylbenzene (PDMS-DVB 65 microm) and Carbowax-divinylbenzene (65 microm). The method was developed using spiked natural waters such as tap, river, sea and lake water in a concentration range of 0.5-50 microg/l. All the tested fiber coatings have been evaluated with regard to sensitivity, linear range, precision and limits of detection. Typical RSD values (triplicate analysis) in the range of 3-10% were obtained depending on the fiber coating and the compound investigated. The recoveries of biocides were in relatively high levels 60-118% and the calibration curves were reproducible and linear (R2>0.990) for both analytes. The SPME partition coefficients (Kf) of both compounds were also calculated experimentally in the proposed conditions for all fibers using direct sampling. Finally the influence of organic matter such as humic acids on extraction efficiency was studied, affecting mostly Sea Nine 211 uptake by the fiber. Optimum analytical SPME performance was achieved using the PDMS-DVB 65 microm fiber coating in ECD and FTD systems for Sea Nine 211 and Irgarol 1051, respectively.     

Solid surface mapping by inverse gas chromatography

Inverse gas chromatography (IGC) at infinite dilution, is a technique for characterising solid surfaces. Current practice is the injection of n-alkane homologous series to obtain the free energy of adsorption of the CH2 group, from which the London component of the solid surface free energy, gamma(d)s, is calculated. A value around 40 mJ/m2 is obtained for poly(ethylene), and 30 mJ/m2 for a clean glass fibre, while the potential surface interactivity of a glass fibre is far greater than that of poly(ethylene). A specific component of the surface, in mJ/m2, should be calculated in order to obtain significant parameters. As applied up to date, when calculating the specific component of the surface energy, the fact that W(sp)a energy values are in a totally different scale than AN or DN values is a major drawback. Consequently, Ka and Kb values obtained are in arbitrary energy units, different from those of the London component measured by injecting the n-alkane series. This paper proposes a method to obtain Ka and Kb values of the surface in the same energetic scale than the London component. The method enables us to correct the traditional London component of a solid, obtaining a new value, where the amount of WaCH2 accounting for Debye interactions with polar sites, is excluded. As a result, an approach to surface mapping is performed in several different substrate materials. We show results obtained on different solid surfaces: poly(ethylene), clean glass fibre, glass beads, chemically modified glass beads and carbon fibre.     

Characterisation of cement pastes by inverse gas chromatography

Two cement pastes, commonly used in concrete formulations, were characterised by IGC at 35-80 degrees C before and after coating with an epoxy resin and a hardener. The cements are mixtures of hydrates in various proportions, such as calcium silicate hydrate (CaO-SiO2-H2O) and calcium hydroxide Ca(OH)2. Apolar and polar probes were used to determine the dispersive and acid-base characteristics of the cement pastes. These materials have high surface energy as judged from the dispersive contribution to the surface free energy (gamma(s)d) values lying in the 50-70 mJ/m2 range at 60-80 degrees C. Examination of the specific interactions permitted to show that the cement pastes are strongly amphoteric species with a substantial predominant Lewis basicity that is in line with the basic pH of their aqueous suspensions. Following coating with an epoxy resin (DGEBA) and a hardener (triethylene tetramine), the surface energy of the cements decreases substantially with the mass loading of the organic material. The surface thermodynamic properties were also correlated with the surface chemical composition as determined by X-ray photoelectron spectroscopy.     

Characterization of polyarylamide fibers by inverse gas chromatography

We determined a group of estrogenic compounds by solid-phase microextraction (SPME) coupled to high-performance liquid chromatography (HPLC) with both ultraviolet (UV) and electrochemical detection (ED). A modified liquid chromatograph was used. Polyacrylate fibers (85 microns) were used to extract the analytes from the aqueous samples. Dynamic and static modes of desorption were compared and the variables affecting both absorption and desorption processes in SPME-HPLC were optimized. Static desorption gave the best recoveries and peak shapes. The performance of the SPME-HPLC-UV-ED method was checked with river water and wastewater. The method enabled estrogenic compounds to be determined at low-microgram l-1 levels in real water samples. Limits of detection were between 0.3 and 1.1 micrograms l-1 using UV detection and between 0.06 and 0.08 microgram l-1 using ED. beta-Estradiol was found in samples from a wastewater treatment plant at concentrations between 1.9 and 2.2 micrograms l-1.     

Glass transitions of polyolefins by inverse gas chromatography

The glass transition temperatures of polypropylene, poly-1-butene, polyisobutylene, and an ethylene-propylene (EP) copolymer have been determined by inverse gas chromatography. The results are consistent with those determined by other procedures. When applied to low-, medium- and high-density polyethylene, values of ?35, ?25, and ?18°C, respectively, were obtained. Because of the fact that the chromatographic technique involves essentially a sensitive detection of free volume in a polymer, it is suggested that these values represent T_g if it is defined as an iso-free volume state of the amorphous phase of the polyethylene.     

Use of pervaporation for separating azeotropic mixtures using two different hollow fiber membranes

The performance of a “two-membrane column” was demonstrated for the separation of water-ethanol and water-isopropanol azeotropic mixtures. The cellulose acetate and silicone rubber membranes which were employed for the strippers showed opposite permselectivity towards each component of the mixtures. The two strippers were connected together with liquid pumps installed between them. A great increase in overall separation factor (over 100) was obtained. The degree of separation was dependent upon the ratio of feed to reject rate. Azeotropic mixtures were successfully separated by using the two-membrane column. This column is expected to provide us with an energy-saving, high purity separation process     

Use of inverse gas chromatography to account for the pervaporation performance in monitoring the oxidation of primary alcohols

The oxidation of n-propanol and n-butanol to their corresponding aldehydes was monitored by the pervaporation technique. Mass transfer phenomenon that occurs in the pervaporation process was confirmed by the results of inverse gas chromatography. Polydimethylsiloxane (PDMS), a hydrophobic polymer widely employed as a membrane in pervaporation technique, was evaluated as a stationary phase in this study. The retention times of the different molecules probes (n-propanol, n-butanol, propionaldehyde, and butyraldehyde), molecules involved as reactants and products in the oxidation reaction, gave an insight into the extent of the interactions between each of these molecules and the stationary phase. The infinite dilution conditions allowed to measure the infinite dilution activity coefficient, gamma(infinity), and the specific retention volume, V(g)(0), and to estimate the Flory-Huggins parameter interactions, chi(12)(infinity). The magnitudes of these parameters threw some light on the permselectivity of the membranes in the pervaporation operation.     

Examination of polyolefins-organic compounds interactions by inverse gas chromatography

The investigations of interactions between polyolefins and test solutes at temperatures 58–122°C were carried out in the work. The test solutes were intentionally selected as representatives of the most important groups of compounds occurring in technological oils, which may be used as additives in conditions of industrial decomposition of polyolefins in Poland. For this purpose both the Flory-Huggins theory and inverse gas chromatography (IGC) were used. On the basis of retention data the values of both interaction and solubility parameters of analyzed polymers were determined. Solubility parameter δ and interaction parameter χ are related to some heat quantities e.g. excess free energy of mixing. It was observed influence of molecular mass and existence of chain branches on the values of the parameters. The obtained values allowed determination of influence of composition change of typical technological oils on their interactions with polymers and, at the same time, on course of charge preparation in these processes.     

Aspects of polymer surface characterization by inverse gas chromatography

The inverse gas chromatographic method has been used to evaluate dispersive surface energies and acid/base interaction values for a styrene/maleic anhydride copolymer over a substantial temperature range. Surface energy calculations require knowledge of the dimensions of adsorbed molecules; conventional values of these for linear alkanes result in reliable surface energy data at near-ambient temperatures. Above about 60°C, however, more reliable surface energy data are obtained when the dimensions of the adsorbed species are corrected by density/temperature variations of the vapors. The copolymer studied was shown to be amphoteric, but with an appreciable prevalence of basic surface sites. © 1994 John Wiley & Sons, Inc.     

The study of reversed phases by inverse gas chromatography

Summary The surface properties of three silica-based reversed phases have been studied by inverse gas chromatography. Theoretical deduction indicates that there is a linear relationship between the molar deformation polarisation of the test solute (P_D) and the dispersive interaction energy between the solute and the C18 and non-bonded silica surfaces. The specific interaction energy between the solute molecule and the silica surface (-G^SP) can be measured as the vertical distance between the solute experimental retention data point (RTl_nV_N) and the n-alkane RTl_nV_N vs P_D calibration line. From multiple regression analysis of-G^SP data with proton acceptor solubility parameter {ie290-1} and orientation solubility parameter {ie290-2} as variants, two coefficients can be obtained related to the influence of the residual silanol groups and the trace metal impurities.     

Study of a rigid-chain dendrimer by inverse gas chromatography

A fourth-generation rigid-chain pyridine-containing polyphenylene dendrimer is studied by inverse gas chromatography. Two types of sorbates are investigated: C₇-C₁₁ n-alkanes and C₆H₆-C₆H₅C₅H₁₁ alkylbenzenes. In the range 35−150°C, specific retention volumes of the indicated sorbates are measured and their solubility coefficients are calculated. It is shown that aliphatic sorbates exhibit reduced solubility coefficients in the aromatic dendrimer compared to those observed for aliphatic polymers and the earlier studied carbosilane dendrimer. At the same time, alkylbenzenes are characterized by enhanced solubility coefficients and this effect is more pronounced for the first members of the homologous series. An analysis of excess partial molar thermodynamic functions shows that π-electron interactions in the dendrimer and among dendrimer and aromatic sorbates are responsible for the thermodynamic properties of the dendrimer under study.     

Determination of glass temperature of polymers by inverse gas chromatography

Inverse gas chromatography (IGC) is an attractive technique for polymer characterization due to possible simultaneous determination of various physicochemical properties of polymer systems merely from retention times of selected sorbates. The technique is especially advantageous to polymers that cannot be characterized by conventional methods. In this review, the utilization of the method for glass transition determination of homopolymers, copolymers and polymer blends is described. Advantages and drawbacks of the IGC method over traditionally used methods for glass transition temperature determination is discussed, along with the most important parameters that influence the precision and accuracy of the glass transition temperature (T(g)) measurements.     

反气相色谱法测定锌镁铝类水滑石的表面性能

采用水热合成法制备了锌镁铝类水滑石(ZnMgAl-HTLC),利用X射线衍射仪(XRD)对ZnMgAl-HTLC的晶体结构进行了表征,并以一系列非极性和极性分子为探针分子,采用反气相色谱法(IGC)研究了ZnMgAl-HTLC的表面性能.结果表明:XRD特征衍射峰窄、尖、高,水热合成法能够制得纯度较高的ZnMgAl-HTLC; ZnMgAl-HTLC表面吸附自由能小于零,表面色散自由能最大为6.02 mJ/m²,酸碱作用自由能最大为5.33 kJ/mol,吸附焓为43.6 kJ/mol,吸附熵为0.15 kJ/mol.本文的反气相色谱方法对研究锌镁铝类水滑石的表面性能具有重要的指导意义.     

反气相色谱法表征漆酚钛螯合高聚物的表面性质

漆酚钛螯合高聚物(UTP)具有优异的耐强酸、耐强碱、耐盐类溶液、耐多种有机溶剂和耐热性能。为进一步扩大其应用领域提供理论和实验依据,采用反气相色谱法(IGC)测定了UTP在70、80、90、100和110 ℃下的表面色散自由能和表面Lewis酸碱常数。以正戊烷(C5)作为标定色谱死时间的探针分子,正己烷、正庚烷、正辛烷和正壬烷作为非极性探针分子,计算了不同温度下UTP的色散表面自由能;以四氢呋喃、丙酮和三氯甲烷作为极性探针分子,计算得到了UTP表面的酸碱作用吸附自由能和吸附焓。实验结果表明: 在70、80、90、100和110 ℃时UTP的色散表面自由能分别为37.68、33.53、35.92、24.01和31.32 mJ/m2; UTP为弱的Lewis碱,Lewis酸常数Ka为0.1853,碱常数Kb为0.9662。这一结果对研究漆酚金属螯合高聚物的表面性质与应用具有指导作用。     

Surface characterization of modified glass fibers by inverse gas chromatography

The dispersive component of the surface free energy _d ^s of glass fibers and their acid-base interaction can be evaluated by the measurement of specific retention volumes of several kinds of probe molecules by use of an inverse gas chromatography. The effect of the treatment of glass fibers with silane-coupling agents was also evaluated. The specific retention volumes of n-alkanes changed linearly with theirC number or vapor pressure. Those of polar molecules varied with their donor number (DN) or acceptor number (AN). The _s ^d values and electron-accepting or donating abilities depended upon the kind of functional groups contained in the coupling agents.     

Surface energy of solid catalysts measured by inverse gas chromatography

The time separation of experimental surface energy on Pt-Rh bimetallic catalysts, together with the time-independent rate constants for adsorption and desorption of O(2), CO, and CO(2) on them, is described, applying the reversed-flow version of inverse gas chromatography. The standard free energy of adsorption DeltaG(z.plims;) and its probability density function over time, together with the geometrical mean of the London parts of the total surface free energy (gamma(L)(1)gamma(L)(2))(1/2) of the adsorbed probe and the solid surface, accompanied by the relevant probability density functions over time are also calculated. The time-resolved phenomena lead to quite varying values of DeltaG(z.plims;), (gamma(L)(1)gamma(L)(2))(1/2), and the distribution functions as time passes, their maximum values being given by the catalyst containing a Pt:Rh = 3:1 weight ratio of the active phase for all adsorbed gases. The conclusion is reached that the surface energy measured as described can be used as a good measure for catalyst characterization.     

Thermodynamics of miscible polymer blends studied by inverse gas chromatography

Use of inverse gas chromatography for the investigation of polymer-polymer interactions is compromised by a dependence of the measured polymer-polymer interaction coefficient, B₂₃, on the chemical nature of the probe in contradiction to theory currently used. We have developed a procedure whereby the “true” B₂₃, may be extracted from the probe dependent data. Additionally a theory of mixing based on a multidimensional solubility parameter approach has been developed. The new theory has been used to predict the polymer-polymer interaction coefficients and these are compared with experimentally determined values on several miscible blends.     

Acid/base characterization of sepiolite by inverse gas chromatography

Summary The surface properties of sepiolite were investigated by inverse gas chromatography. It is shown that the value of the dispersive component change uniformly with temperature, while the values obtained for the parameters K_A and K_D indicate an acidic character for the sepiolite surface.     

Physicochemical measurements by the reversed-flow version of inverse gas chromatography

Since the first publication on the method, reversed-flow gas chromatography has been used to "separate" physicochemical quantities by measuring the value of one in the presence of another. The experimental arrangement consists of a small modification of a commercial gas chromatograph, so that it includes a four- or six-port gas sampling valve, and a simple cell placed inside the chromatographic oven. This cell suppresses the effects of the carrier gas flow on the physicochemical phenomena taking place in the stationary phase. These phenomena pertain to chemical kinetics, diffusion in gases, liquids and surfaces, mass transfer across gas-liquid and gas-solid boundaries, local adsorption on heterogeneous solid surfaces, etc.