Preparation,evaluation, and comparison of wide bore (320 μm) and narrow bore (50 μm) cyanosilicone-coated capillary columns for gas chromatography

The preparation of wide bore (320 μm) and narrow bore (50 μm) fused silica capillary columns is described for immobilized cyanopropyl substituted silicones containing 60 and 88% substitution. The effect of high temperature deactivation with cyanopropylcyclosiloxanes was studied with a special test mixture. Curing was achieved with dicumyl peroxide or azo-tert-butane. The columns were evaluated and compared in terms of efficiency, activity, polarity, and temperature stability. Different coating methods were compared for the narrow bore columns. The activity of the 60% cyanopropyl columns that had been immobilized with dicumyl peroxide was significantly larger than for azo-tert-butane immobilized columns. The polarity of polar columns appeared to depend greatly on column temperature and is completely different for wide and narrow bore columns.     

The selectivity and polarity of carbon layer open tubular capillary columns modified with a polar liquid phase

The polarity of carbon layer open tubular (CLOT) columns coated with a layer of non-porous graphitized carbon black (Carbopack B) modified with an appropriate amount of polar polyglycol liquid phase has been evaluated and compared with that of standard polar (Supelcowax-10) and non-polar (SPB-1) bonded phase open tubular columns. The efficiency and selectivity were measured at various temperatures and the polarity of the columns was evaluated by use of McReynolds' constants and the difference in apparent carbon number, ΔC of linear alkanes and alcohols. The polarity of the CLOT column was found to depend on temperature, and changing the analytical conditions therefore enabled the separation of compounds of different polarity whose reciprocal position and resolution were affected by temperature. The application of calculation methods which enable programmed temperature retention times to be predicted from isothermal data was also found to be possible when the polarity of the CLOT column changes with temperature.     

Serially coupled capillary columns supercritical fluid chromatography with a coupling restrictor.

A serially coupled column system for capillary supercritical fluid chromatography was constructed by connecting two capillary columns of different polarities using or without using a coupling restrictor. The influence of the column sequence, the size of the coupling restrictor and the column temperature on the polarity of the system were studied. The system without a coupling restrictor (the directly coupled system) provided an intermediate polarity between two columns, depending on the column geometry, such as the film thickness and column length, although it slightly shifted to that of the first column. In the system with a coupling restrictor, the contribution of the second column to the overall retention increased with its resistance. The use of a coupling restrictor allowed to control the polarity of the coupled system virtually over the whole range between two columns. The temperature was an additional effective parameter for tuning the polarity of the system.     

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.     

Mixed phases of Superox 20M and OV-1 in fused silica and glass capillary gas chromatography

Summary Mixed phases of Superox 20M and OV-1 can be coated homogeneously on the untreated wall of fused silica capillary columns. Excellent columns with regard to efficiency, inertness and thermal stability can be obtained. (CE>95% and MAOT250°). The polarity and selectivity were ascertained with Rohrschneider-Reynolds probes and a capillary polarity test mixture. The analysis of an essential oil mixture illustrates the possibilities of mixed phases in practical capillary GC.     

Fused silica substrate effects on capillary column performance

The effect of a pretreatment step on the polarity of fused silica capillary tubing prior to coating was evaluated. Columns were tested prior to and after coating with a 50% phenl stationary phase, and the chromatographic findings were compared. The results confirmed that the polarity of the fused silica substrate affects the inertness and reproducibility of the final coated columns.     

Azulene-Modified Polysiloxanes as Gas Chromatographic Stationary Phases: Comparison of the Separatory Properties of Azulene and Naphthalene

Azulene is an aromatic molecule with interesting properties, most notably a permanent dipole moment of 1.08D. This degree of polarity in the absence of heteroatoms is quite rare and offers potential for use in unique gas chromatographic stationary phases. Here, we report the first examples of azulene-derivatized stationary phases for gas chromatographic separations. Poly(dimethyl/azulenylmethyl) siloxane polymers containing 15 and 35% of an azulene derivative were synthesized, coated on capillary columns, and evaluated. To compare the effects of increased polarity vs. the effects of polarizability, isomeric naphthalene analogues were also prepared, coated, and evaluated. The coated phases displayed efficiencies up to 2700 plates/m. For both azulene and naphthalene columns, retention increased as substitution level increased. The more polarizable naphthalene columns tended to retain analytes more strongly. Columns were also evaluated for the separation of several different mixtures of isomers against a commercial HP-5 column. All azulene and naphthalene columns exhibited separations comparable to the commercial column. The solvation thermodynamic parameters phases were measured, showing an excellent linear relationship and no change in the mechanism of interaction over the temperature range measured.     

偶氮特异丁烷引发交联OV-1701石英弹性毛细管色谱柱的研究

ATB(偶氮特异丁烷)是一类性能良好的自由基引发剂、用它引发交联OV-1701石英弹性毛细柱,交联度大于96％,柱子内壁惰性,柱效高,热稳定性好,交联前后柱极性无明显变化,文中还对交联条件和反应机理进行了研究和探讨。     

烷基化和硅烷化β-环糊精手性固定相的研究

合成了2,6－O－二戊基－3－O－三甲基硅烷基－β－环糊精,采用超动态法,成功地将其涂渍到弹性石英毛细管柱,经测试,柱性能稳定、寿命长、置于空气中一年半仍具有较高的柱效和手性拆分能力,利用该柱,分离了醇、酮、烯烃等一些对映体,考察了不同稀释剂配比所得固定相的立体选择性。     

纤维素衍生物作为毛细管气相色谱新型固定相的研究

以纤维素三苯甲酸酯、纤维素三苯基氨基甲酸酯以及二者的混合物为固定相,制备了新型毛细管气相色谱柱,最高柱效达到2580板/米。其能对一些难分离物质对、位置异构体以及手性化合物进行拆分,如对丙氨酸的分离因子可达到1·13。此外,还研究了毛细管柱的极性、选择性以及保留机理。结果表明,该类聚合物是一类很有前景的新型气相色谱固定相。     

气相色谱柱对多溴联苯醚分析的影响

基于气相色谱-电子捕获检测器法对11种代表性多溴联苯醚进行分析,考察不同类型气相色谱柱对多溴联苯醚分离分析的影响. 结果表明:色谱柱极性是影响分离和响应的主要因素,极性较大的固定相上多溴联苯醚各单体的保留时间变长,响应降低,尤其是高取代多溴联苯醚的响应受到的影响最大. 柱长较短、液膜较薄的色谱柱有助于高取代多溴联苯醚的分析. 不同品牌的色谱柱受生产工艺的影响,对多溴联苯醚的响应产生较大影响.     

Spectral presentation of chromatographic information in qualitative organic analysis

The possibility of using noninterpolatory retention characteristics in qualitative gas-chromatographic analysis was examined. The retention data were obtained using packed columns with stationary phases of various polarity connected in a series. An identification unit was designed. Identification procedures were developed.     

Glass capillary columns with liquid crystalline stationary phases for gas chromatography. The influence of the pretreatment of the inside tube wall

Summary The importance of capillary columns prepared with a liquid crystalline stationary phase are increasing. It is known that the interaction of the liquid crystals molecules with the glass capillary wall may strongly influence selectivity and efficiency of the column. The paper reports on systematic investigations on the correlations between the pretreatment of the inside glass capillary surface, the chemical nature of the liquid crystal and the chromatographic properties of the columns obtained. Two types of matrix were investigated: barium carbonate and barium carbonate with subsequent deactivation with Carbowaxes. Three liquid crystals with different relative polarity (terminal group polarity) and nematic mezophase transitions were used. Deposition of barium carbonate, if necessary, with a secondary Carbowax treatment was found as an excellent capillary wall pretreatment method. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

A study of chromatographic properties of liquid crystalline polyacrylates using WCOT columns in gas chromatography

Liquid crystalline polyacrylates (LCPAs) are evaluated as stationary phases for capillary gas chromatography (CGC). Aromatic hydrocarbons as well as polar isomeric compounds are used as test solutes to compare the polarity of the LCPAs with a conventional polysiloxane column and a Carbowax 20M column. The relative polarity of the columns with respect to change in the lateral and terminal substituents is also discussed. Lateral substitution, polarity of the terminal group, together with the solute size, affect the LCPA selectivity.     

Chromatographic properties and polarity evaluation of poly(1-trimethylsilyl-1-propyne) and poly(1-phenyl-1-propyne)

The chromatographic properties of poly(1-trimethylsilyl-1-propyne) (PTMSP) and poly(1-phenyl-1-propyne) (PPP) were studied by gas chromatography using packed columns. The selectivity and efficiency of columns packed with PTMSP and PPP were compared to the data obtained for columns with other known adsorbents and stationary phases. The McReynolds and Rohrschneider constants, on the basis of which the polarity of the new phases was evaluated, were calculated. The results of the investigation of chromatographic properties allow PTMSP to be brought in line with the polymeric adsorbents Porapak Q, Porapak QS, and Chromosorb 106, while PPP, with the methyphenylsilicon phases SE-52 and OV-3.     

Classification and comparison of capillary columns by determination of the solution enthalpy of polar and non polar probes

The behaviour and separation characteristics of capillary columns containing different stationary phases (bonded methyl- and methylphenylsiloxanes and polyglycols, and carbon layer and porous polymer) were classified and compared by measuring the values of the solution enthalpy DeltaHs of n-alkanes and 1-alcohols at various temperatures. The difference in DeltaHs values between straight-chain 1-alcohols and n-alkanes with the same number of carbon atom (DeltaDeltaHs) does not change with changing temperature when gas-liquid partition stationary phases are used, but depends on the column composition and polarity and therefore permits to evaluate the influence of polarity on the solute-solvent interaction. The trend of the DeltaDeltaHs values is correlated with that of the DeltaC parameter and with the McReynolds' polarity constants.     

Using principal component analysis for the study of the retention behaviour of phenol derivatives under reversed-phase conditions

Summary The retention time of 11 ring-substituted phenol derivatives was measured on six different reversed-phase HPLC columns and the log k, theoretical plate number (N) and asymmetry factor (F) values were calculated for each solutes on each column. The similarities and dissimilarities among the columns and solutes were elucidated by principal component analysis followed with nonlinear mapping technique and cluster analysis. Calculations indicated that the retention characteristics of porous graphitized carbon stationary phase considerably deviate from those of octadecyl- and hexyl-coated silica, octadecyl-coated polystyrene-divinylbenzene polymer and polybutadiene-coated alumina. The differences among these columns were markedly smaller. The retention behaviour of aminophenols differed from those of other phenol derivatives proving the importance of molecular polarity in the retention. It was established that the mode of calculation slightly modifies the similarity and dissimilarity among the columns and solutes, therefore, the use of more than one calculation method is proposed.     

High temperature gas chromatography on narrow bore capillary columns

The use of high-temperature-stable, medium polarity glass capillary columns coated with immobilized PS-090 (a 20 % diphenyl-substituted, CH₃O-terminated polydimethylsiloxane) has made it possible to analyze routinely, and with good separation efficiency, high molecular weight compounds such as triglycerides and free base porphyrins. Cold on-column injection was used throughout this work to avoid discrimination against involatile compounds, and disposable (fused silica) retention gaps were used to protect the column against contamination with involatile material. On-column injection into narrow bore glass columns was achieved by using glass-to-silica connections to attach wider bore (0.2 mm i.d.) deactivated fused silica tubing to the columns.     

Kováts' coefficients for predicting polarities in silicone stationary phases and their mixtures

Summary A correlation between the retention polarity and the Kováts' coefficient has been found for a number of commercial stationary phases used in gas chromatography. The correlation has been used to predict the polarity of a few mixed stationary phase columns prepared as binary mixtures of OV-101 with OV-25, DC-550 or Carbowax 20M, and also mixtures of OV-225 with SP-2340. A linear relationship was found between polarity and mixture composition. The temperature dependence of the Kováts' coefficient was investigated and found to increase linearly with temperature, the rate of increase depending on the polarity of the stationary phase, with greater increases for more polar stationary phases.