Modification of glass capillary gas chromatographic columns by alkylation of the glass surface with pentafluorobenzyl bromide

Summary Glass surface alkylation with pentafluorobenzyl (PFB) bromide yields glass capillary gas chromatographic columns with modified retention characteristics. Glass-alkylated OV-225 columns have been tested in the analysis of PFB fluoroacetate, and the substantial increase in retention time of this highly volatile compound was found to improve the precision of analysis. PFB-alkylated columns should prove generally useful in gas chromatographic analysis of small relative molecular mass compounds.     

Analytical aspects of capillary gas chromatography of lower fatty acids [up to C18]

The principal aspects influencing analytical capillary gas chromatography of fatty acids up to C18 have been evaluated. Selected fundamental problems of interlaboratory exchange of retention data were problems of defined temperature in commercial thermostated air baths, of capillary tubing, and of stationary phases. A modification of commercial thermostats has been proposed in order to secure a defined temperature for glass capillary columns. It has been found that retention data of fatty-acid methyl esters can be measured under standard conditions with the same accuracy as retention data of hydrocarbons on squalane. Metal capillary columns coated with Apiezon L were found to be unsuitable for the analysis of fatty-acid methyl esters when compared with the results of their quantitative analysis in packed Apiezon L and polar capillary columns. Possibilities of a nontraditional statistical evaluation of the results of measurements are suggested. A program in FORTRAN IV language is given for the calculation of Kovats' retention indices for fatty-acid methyl esters.     

Behavior of n-alkanes on poly(oxyethylene) capillary columns. Evaluation of interfacial effects

The solvation behavior of n-alkanes on poly(oxyethylene) was studied employing capillary gas chromatography. Interfacial effects were discriminated and evaluated through the analysis of retention data from six commercial fused-silica capillary columns, having film thicknesses of 0.15-5 microm. Expressions for the mixed retention mechanism in capillary columns were deduced from assumptions of a general character. Partition coefficients were determined for the n-alkanes up to 28 carbon atoms, at temperatures ranging from 40 to 240 degrees C. In agreement with other authors, it was observed that interfacial phenomena contribute poorly to the chromatographic retention, being negligible over 140 degrees C for homologues with less than 16 carbons.     

An experimental investigation of retention of liquids in corners of a square capillary

The retention of liquids in the corners of a 0.03-cm square capillary after the passage of a gas slug was studied experimentally as a function of capillary number in the range from 10(-3) to 10(-6). In gas-wetting liquid systems, for capillary number greater than 5 x 10(-4), the retention of a wetting liquid in the corners showed a strong dependence on the capillary number; i.e., the retention of the liquid decreased with decreasing capillary number. For capillary number less than 10(-4), the retention of a wetting liquid was found to be determined by the capillary forces and the rate (or viscous) effect was negligible. In gas-oil-water systems involving double displacements--gas was displacing oil which was in turn displacing water--the total retention of water and oil vs capillary number curve showed the same trend as the retention of a wetting phase in a gas-wetting liquid system. However, because of the viscous effect, the water retention showed a continuous decrease with decreasing capillary number and could be lower than the capillary equilibrium value at very low capillary numbers. As a result of this, the oil retention vs capillary number curve in the double displacement process showed a minimum; i.e., oil retention increased with decreasing capillary number in the range of very low capillary numbers.     

非等间隔PCBs保留指数体系在光解行为研究中的应用

利用Ｃｈｕ等已建立的多氯联苯（ＰＣＢｓ）非等间隔保留指数体系,由文献中的相对保留时间计算出全部２０９种ＰＣＢｓ同类物（Ｃｏｎｇｅｎｅｒ）的保留指数（ＩＰＣＢ）。利用ＩＰＣＢ结合ＧＣ－ＭＳ对ＰＣＢ８７、ＰＣＢ１３８和ＰＣＢ１６９三种同类物的光解产物进行了定性分析,发现其光解产物主要为低氯代联苯。实验结果证明,非等间隔保留指数体系ＩＰＣＢ在ＰＣＢｓ同类物的定性分析中具有准确、实用、快捷、方便等优点。     

毛细管气相色谱活数据库定性

活数据库方法有效地解决了毛细管气相色谱程序升温下的无标样定性问题,详尽讨论了活数据库的方法原理和影响因素,最后以汽油为例,说明活数据库定性方法的实用性。     

The use of predicted boiling points for the identification of halobenzenes and substituted phenols in capillary gas chromatography

Quantitative correlations between physicochemical parameters and structure of various solutes and their gas chromatographic behavior were investigated in order to predict the retention values. The identification of unknown samples in gas chromatographic routine analysis of environmental samples is enhanced by the use of these correlations in conjuction with other chromatographic methods and with mass spectrometry. The boiling points of many compounds are easily found in literature and therefore their correlation with retention values obtained in isothermal or programmed temperature analysis permit restriction of the choice of names of unknown compound to within a narrow range. The correlation between the boiling points and the retention times of chloro- and bromo-benzenes and of some chloro- and nitro- substituted phenols was investigated on non-polar capillary columns and permitted the tentative identification of many compounds belonging to these homologous series.     

Coupling miniaturized liquid chromatography to capillary gas chromatography (micro-LC-CGC): Possibilities of reversed phase LC

Retention gaps with different polarity treatments were evaluated for reversed phase solvents. Aminopropyl- and cyanopropyl-deactivated retention gaps showed the best results for methanol-water mixtures. A reversed phase packed fused silica capillary LC column is connected on-line with a capillary gas chromatography column. The combination was used for the analysis of diazepam in urine. Volume overloading on packed fused silica columns without loss of too much efficiency was demonstrated for propranolol.     

简易毛细管气相色谱冷柱头进样法

介绍了一种在无冷柱头进样器和特殊注射器情况下简便可行的冷柱头进样技术。以海洛因、秋水仙碱、正三十烷醇为研究对象，考察了本方法的定性、定量偏差，提出两种溶质聚焦方法。     

Optimization of operating parameters for glass capillary column gas chromatography

The relationship between analysis time and separation with glass capillary columns was studied. Optimal operating parameters for achieving the shortest analysis times consistent with degree of separation were determined experimentally. It was found that the optimum column temperature is governed by retention characteristics of the solutes and the optimum column length by the required magnitude of separation. The optimum carrier gas flow-rate was found to be a function of the column length. Emphasis is placed on using capillary column length as an operating parameter.     

填充毛细管液相色谱-毛细管气相色谱在线联用分析八角茴香挥发油

首次将填充毛细管高效液相色谱-毛细管气相色谱在线联用技术(μ-HPLC-CGC)用于分离分析八角茴香果实的挥发油成分。液相色谱选用氰基分析柱(250 mm×0.32 mm i.d.),正己烷-乙腈-二氯甲烷(体积比为80∶8∶12)为流动相,对挥发油样品做族组分分离,得到的5个族组分被依次存放在多位储存接口内,然后不分流分别转入毛细管气相色谱仪做详细分析。气相色谱柱由10 m×0.53 mm i.d.保留间隔柱和30 m×0.53 mm i.d.×1.0 μm SE-54分析柱组成。采用了不分流柱内进样模     

Compositional studies of high-temperature coal tar by GC/FTIR analysis of light oil fractions

Summary A method for determination of the composition of the light oil fractions in high-temperature coal tar by means of distillation, followed by gas chromatography on a crosslinked fused-silica, capillary column coated with optimum amount of stationary phase and identification by capillary gas chromatography/Fourier transform infrared spectrometry combined with GC retention indices (GC/FTIR-RI) is described. This method was effectively used to identify complex mixture such as coal tar without any standard samples, especially, adapted for isomeric compounds. More than 60 and 50 compounds were also separated and identified respectively in light oil fractions. This shows the capability of the capillary GC/FTIR combined with GC retention indices to identify isomers not accomplished by GC/MS.     

Fast gas chromatography: packed column solvating gas chromatography versus open tubular column gas chromatography

Packed capillary column solvating gas chromatography (SGC) and open tubular column gas chromatography (GC) were compared with respect to their potentials for fast separations. A recently introduced "universal" peak capacity equation was used to compare the performance of these two methods. The effects of various factors on peak capacity were investigated. Results demonstrate that retention factor and column efficiency are the main factors affecting peak capacity for fast separations. Packed columns produce both high retention factors and high selectivities. While high efficiencies and high peak capacities can be demonstrated by both techniques, open tubular column GC can surpass packed capillary column SGC in both measurements, except for the case of the analysis of simple mixtures in short analysis times, where retention factor and selectivity become important. Practical aspects such as pressure drop and sample capacity are compared for SGC and open tubular column GC. It was found that packed column SGC demonstrates higher sample capacities, but requires much higher column inlet pressures than open tubular column GC. A variety of mobile phases can be used for packed column SGC, which can provide high solvating power for large and polar compounds.     

Variable splitter for regulation of the solvent evaporation rate in the coupling of liquid chromatography with gas chromatography

A system is described which accelerates the solvent evaporation rate in the retention gap. The evaporation is due to a saturation effect of the carrier gas stream, and a considerable increase in evaporation rate is obtained by inserting a split outlet between the retention gap and the capillary separation column in the gas chromatograph. By varying the backpressure of the spliter device, the flow rate through the retention gap can be adjusted and so too the evaporation rate. The evaporation process was monitored by inserting a dectecter in the split outlet line. The technique was applied to the on-line LC trace enrichment/GC analysis of water containing a mixture of polycyclic aromatic hydrocarbons.     

Using Bezier curves for the calculation of retention indices of polycyclic aromatic hydrocarbons in the so-called Lee's scale in temperature-programmed gas chromatography with mass spectrometry detection

The retention indices of some polycyclic aromatic hydrocarbons (PAHs) separated by temperature-programmed gas chromatography are computed by smoothing reference data with Bezier curves of orders 6 are more consistent with the scheme of this retention parameter, and they present standard deviations systematically smaller than those associated with classical retention indices. The Bezier curve possesses the property of local control, (i.e., their graphs are modified only in the neighbourhood of the displaced point). The values thus obtained were compared with the corresponding ones calculated in a classical way. Detailed statistical analysis is presented to describe the retention indices of PAHs expressed in the so-called Lee's scale as a function of retention temperatures (in degrees C). As a training set, experimental retention data of PAHs obtained on a PE-5 phase is used for correlation. As prediction sets, literature experimental retention indices expressed in the so-called Lee's scale obtained on a DB-5 slightly polar stationary phase are applied for comparison. The method developed is successfully used for estimating and predicting the capillary gas chromatography retention index of PAHs.     

Polycyclic Aromatic Hydrocarbons Formation from Fuel and Additives Combustion

A study has been made of the effect of additives to the fuel of a turbulent diffusion flame on the formation of soot and polycyclic aromatic hydrocarbons (PAHs). Fuels containing a polystyrene thickener doped with benzene proved to have many advantages over unthickened fuels. Most significant were an increase in the burning time and the flash point. Nevertheless, polystyrene and benzene additives to a considerable extent increased the formation of soot and PAHs. The analysis of PAHs in this study was made by capillary gas chromatography (GC) and capillary gas chromatography/mass spectrometry (GC/MS). A total of 42 individual compounds were characterized by their retention indices and mass spectra.     

High resolution capillary gas chromatography of aromatic compounds in multicomponent hydrocarbon mixtures

The scope of the principal techniques employed for the analysis of hydrocarbon mixtures is discussed, with emphasis on the analysis of one and two ring aromatic compounds by single column capillary gas chromatography. The paper considers both the column and the selection of the temperature regime (isothermal and temperature programmed). Much space is devoted to the characterization of the compounds by means of retention data.     

Prediction of programmed temperature retention times on linked capillary columns of different polarity

Systems formed by serial connection of capillary columns of different polarity were studied with methods previously used to predict the behavior of linked capillary columns under isothermal conditions and to obtain programmed temperature gas chromatography (PTGC) retention times of the individual columns starting from isothermal data. The two calculation methods were simultaneously applied in order to predict PTGC retention times of the series system starting from isothermal data obtained on the two individual columns. Experimental retention values measured using different temperature programs on the individual columns and on the series systems were found to agree with those calculated.     

Influence of the carrier gas on retention factors of gaseous hydrocarbons on polytrimethylsilylpropyne using capillary gas chromatography

The retention factor and height equivalent of a theoretical plate for gaseous hydrocarbons C₁—C₄ were studied on capillary columns with the layer of the new polymeric adsorbent polytrimethylsilylpropyne (PTMSP) as functions of the nature and pressure of the carrier gas. The retention factor k increases in the series helium < nitrogen < carbon dioxide. The k values depend linearly on the average pressure of the carrier gas in a capillary column with the adsorption PTMSP layer.     

Faster GC analyses performed by flow programming in short capillary columns

The technique of programming the carrier gas flow rate in gas chromatography, especially in connection with the use of capillary columns shorter than 10 m can significantly accelerate GC analyses. Equations for calculation of the parameters of the exponential flow function and retention data are described. The effects of flow programming in a short capillary column are shown in a few chromatograms. Different programming rates are tested and compared with temperature programming.