Chemometric study of retention on binary stationary phases in gas chromatography

Using gas chromatography, data analysis is performed on a dataset consisting of 486 retention indices, 27 standards (ramified alkanes, aliphatic alcohols, and aromatic compounds), 6 pure and binary stationary phases, and three temperatures. The behavior of the pure stationary phases (OV-3, OV-225, OV-61-OH, and OV-1701-OH) and the binary stationary phases (OV-3/OV-225 and OV-61-OH/OV-1701-OH) at different temperatures (60°C-100°C) is investigated with factor and topological analysis. The influence of temperature and the nature of the mixed stationary phases on the retention indices is studied by correspondence factor analysis (CFA). The non-additivity of the retention properties of the pure phases used as mixed phases is clearly established by CFA. The topological analysis of the substituent's effect is investigated with a DARC/PELCO procedure and shows the particular influence of the stationary phase composition on the retention. The substituent effect is measured for the pure and binary stationary phases at various temperatures. The evolution of the substituent effect from the pure stationary phases to the binary phases is discussed.     

Prediction of the chromatographic retention of saturated alcohols on stationary phases of different polarity applying the novel semi-empirical topological index

The novel semi-empirical topological index (I_ET), previously developed by Heinzen and Yunes, was extended to predict the chromatographic retention of saturated alcohols on low polarity stationary phases (OV-1). The predictive ability of I_ET was also verified on stationary phases of different polarity (SE-30, OV-3, OV-7, OV-11, OV-17 and OV-25). Simple linear regressions between the retention indices and the semi-empirical topological index (RI=a+bI_ET) were established for each stationary phase separately, showing good statistical parameters. Statistical analysis showed that the QSRR model used on stationary phases of low polarity (OV-1) has high internal stability and good predictive ability for external groups. The polarity of the SE-30, OV-3, OV-7, OV-11, OV-17 and OV-25 stationary phases, indicated by retention polarity (P_R) given by Tarján et al., is reflected in the ‘a’ (intercept) and ‘b’ (slope) coefficients of the equations obtained for each of these phases. The linear relationship between the ‘a’ coefficient and P_R showed satisfactory statistical quality. Thus, it was possible to generate a single combined model of QSRR, including a parameter that represents the property of the stationary phase P_R. The combined model also has a satisfactory predictive quality, as shown by the plot of calculated versus experimental retention indices for saturated alcohols on six stationary phases of different polarity (r²=0.9956; S.D.=9.54).     

Chromatographic properties of various polysiloxane stationary phases for separation of 2,3,7,8–chloro-substituted dibenzo-p-dioxin and dibenzofuran isomers–a systematic comparison

Glass capillaries coated with four crosslinked and surface-bonded OH-terminated polysiloxanes [PS 347.5, OV-17-OH, OV-225-OH, and OV-240-OH] were compared with commonly used methyl-terminated SP-2330-coated columns with respect to their selectivity for the separation of 2,3,7,8-chloro-substituted dibenzo-p-dioxins and dibenzofurans. The methyl- and phenyl-substituted phases [PS 347.5 and OV-17-OH] exhibit only moderate isomer selectivity which limits their applicability in this field. The examined 3-cyanopropyl-substituted phases [OV-225-OH, OV-240-OH, and SP-2330] allow complete separation of all 2,3,7,8-chlorosubstituted PCDDs and PCDFs. With SP-2330 longer columns are required (50 m) for baseline separation of critical groups of isomers. OV-225-OH was found to be the most suitable phase as to isomer selectivity. In comparison to SP-2330, the analysis times can be reduced by a factor of two.     

Characterization of OV-1/FFAP-mixture coated glass capillary columns used for the separation of free fatty acids

As an alternative to acid pretreated UCON and FFAP capillaries for the analysis of wide-boiling free fatty acid mixtures, OV-1 : FFAP phase mixtures were used on high-temperature silylated inert glass capillary columns. The HETP-carrier gas velocity curves, peak asymmetry factors, coating efficiency, gas phase and stationary phase contributions to the mass transfer resistance were determined for various OV-1 : FFAP ratios. Mixed-phase capillaries showed optimum performance at a 2 : 1 OV-1 : FFAP ratio. The thermal and long-term stability of OV-1-stabilized FFAP columns surpassed those of the UCON and pure FFAP reference column used.     

The preparation of immobilized stationary phase fused silica capillary columns with OV-1701-vinyl deactivation

A new simplified method was developed for the preparation of immobilized stationary phase fused silica capillary columns coated with OV-1-vinyl, SE-54, and OV-1701-vinyl. This methodology includes the application of the moderately polar stationary phase OV-1701-vinyl as a surface deactivation agent that may also participate in the dicumyl peroxide initiated free radical immobilization process. Practical details of the procedure are presented and applications of the laboratory-produced columns are illustrated with capillary gas chromatographic separations of standard mixtures. Possible contributions of the OV-1701-vinyl deactivation layer to both crosslinking and surface bonding in the immobilization process are discussed.     

丙烯腈中微量杂质的毛细管色谱法分析

提出了一种分析丙烯腈中微量杂质的大孔径ＯＶ－１０１和ＯＶ－１７ＳＣＯＴ串联柱及毛细管进样系统。结果表明串联柱具有寿命长和分离效率高的特点,定量分析误差小于４％。     

Purification of OV-17 by supercritical fluid fractionation for fused silica capillary gas chromatography

Commercially available OV-17 was partitioned into a low and a higher molecular weight fraction by supercritical fluid extraction with carbon dioxide. This higher molecular weight fraction is more thermally stable than the original OV-17 due to its more viscous and gum-like nature. Based on the growing evidence in the literature that a deactivating agent for fused silica open tubular columns should be compatible with the stationary phase, a precoat of 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane was applied prior to the static coating of high molecular weight OV-17. Fused silica OV-17 columns prepared in this fashion are stable up to 300°C.     

Gas—liquid chromatography on phenyl-substituted polysiloxane stationary phases,alcohols and alcohol benzoyl derivatives

Retention indices of 54 alcohols and 55 alcohol benzoyl derivatives measured on short stainless steel columns (1 m × 2 mm i.d.) filled with Chromosorb G (AWDMCS (HP)) coated with 5% ($\text{w}\text{w}$) SE-30, OV-3, OV-7, OV-11, OV-17 or OV-25 stationary phases at 100°C, 120°C and 140°C, appear to be very accurate, provided that there is careful control of the Chromatographic process. Values of the temperature dependence of retention index of alcohols and benzoates, and variations of these values with the polarity of the phase used, are given.     

Cyclodextrin derivatives for the GC separation of racemic mixtures of volatile compounds. Part VI: The influence of the diluting phase on the enantioselectivity of 2,6-Di-O-methyl-3-O-pentyl-β-cyclodextrin

As a continuation of previous studies on the use of cyclodextrin derivatives (CD) for the separation of volatile compounds by capillary GC, the influence of diluting phases other than OV-1701 or OV-1701-OH has been investigated. 2,6-Di-O-methyl-3-O-pentyl-β-cyclodextrin (2,6-DiMe-3-Pe-β-CD) was taken as the reference CD derivative, because of the large number of volatile racemates it is able to separate; OV-1701 or OV-1701-OH was chosen as the reference diluting phase. The performance of a column coated with a 0.15 μm film of 10 % 2,6-DiMe-3-Pe-β-CD in OV-1701 was compared with that of analogous columns coated with films of the same thickness containing the same percentage of the CD derivative diluted with stationary phases of different polarity, i.e. PS-086, PS-347.5, and OV-225. Resolution values and separation factors of thirty racemates were used to evaluate the effect of different diluting phases on column performance.     

Influence of the chemical nature of siloxanes on the thermodynamic characteristics of sorption for a series of linear and cyclic saturated hydrocarbons

The thermodynamic characteristics of sorption (Henry’s constants of sorption equilibrium K _sorp, heats of sorption q, and standard entropies of sorption ΔS°) were studied by gas chromatography to describe the behavior of linear and cyclic saturated hydrocarbons on phenylmethylsiloxane HP-5, fluoromethylsiloxane OV-210, and methylsiloxane OV-1. The K _sorp and q values and, correspondingly, the energy of dispersion interactions decrease in the series HP-5 > OV-1 > OV-210. The difference in structures of adamantane, trans-decalin, and decane molecules has almost no effect on the heats of sorption. Henry’s constants increase on going from decane to trans-decalin and, further, to adamantane. This effect becomes more pronounced with an increase in the sorbent polarity (OV-1 < HP-5 < OV-210). The entropy factor can play a key role in sorption processes on siloxanes.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 140–143, January, 2005.     

Immobilization of silicone stationary phases on supports using ozone

Summary Immobilization of silicone stationary phases, OV-1701 vinyl and OV-225 vinyl, on Chromosorb W-AW support was achieved in a simple procedure using ozone as an initiator. A column efficiency of 2400 theoretical plates/meter was obtained.     

Palladium(II) chelate of tetradentate Schiff base as mixed stationary phase for gas chromatography

Bis(acetylacetone)ethylenediiminepalladium(II) (PdAA2en) was examined as a mixed stationary phase with OV-1 on Chromosorb G/NAW 60-80 mesh size for the GC separation of aromatic hydrocarbons, heteroaromatics, alcohols, aldehydes, ketones, esters, and nitro compounds. Forty-two compounds were examined and the GC results were compared with those obtained with 3% OV-1 on Chromosorb G/NAW 60-80 mesh size under similar operating conditions. Improved resolution, peak asymmetry, theoretical plate numbers, and Kovats indices were obtained on the mixed stationary phase of 3% OV-1 + 5% PdAA2en compared to 3% OV-1 column. The stability constant (Km), enthalpies (deltaH), entropies (deltaS), and Gibbs free energies (deltaG) of the GC elution on the column (2 m x 3 mm id) packed with 3% OV-1 + 5% PdAA2en on Chromosorb G/NAW 60-80 mesh size have been calculated. Donor-acceptor complexation in the gas phase is indicated by negative values of enthalpy (-deltaH) within 5.81 to 10.89 kcal/mol and Gibbs free energy (-deltaG) from 1.34 to 4.08 kcal/mol. The retention time transformations on both the phases were calculated and the ratios obtained from the stationary phases 3% OV-1 and 3% OV-1 + 5% PdAA2en were plotted on the x-axis and the y-axis, respectively, and the coefficients of determination for alkanes, aromatic and heteroaromatics, ketones, and alcohols were observed to lie within 0.5253 to 0.9742, indicative of some different kinds of interaction of the two stationary phases with the solutes.     

High resolution chemically bonded fused-silica capillary gas chromatography of organochlorine insecticides and related compounds in arable soil samples

Electron capture gas chromatography with three chemically bonded fused-silica capillary columns (CB-FSCs), OV-17, OV-1701, and SE-52, was performed to evaluate peak separability of 28 organochlorine insecticides and related compounds. Relative retention times and relative peak heights to aldrin were measured and calculated. OV-17 CB-FSC showed the best separability among the three CB-FSCs employed and was applied to analysis of extracts from several soil samples with minimum clean-up procedure. The chromatograms obtained demonstrated steady baseline tracings free of interference. Residue data from soil samples were also tabulated.     

Relationship between the average molecular polarizabilities of polycyclic aromatic hydrocarbons and their retention indices determined on various stationary phases

The Kováts retention indices of 10 polycyclic aromatic hydrocarbons were determined on SE-30, OV-101, SE-52, OV-7 and OV-17 stationary phases. A significant correlation has been found between the retention indices and the average molecular polarizabilities of the analyzed substances. Equations were derived for the direct determination of the average molecular polarizabilities from the retention index values. The influence of the temperature on this relationship is also indicated.     

脂环族酸酐在不同极性气相色谱柱上的性能研究

研究了甲基四氢苯酐、甲基六氢苯酐、萜烯马来酸酐及氢化萜烯马来酸酐等脂族酸酐在HP-1、HP-5、OV-17和FFAP四种不同极性毛细管色谱柱上的色谱性能。分析结果表明,这四种脂环族酸酐均能在OV-17毛细管色谱柱上获得很好的峰形和分离效果。     

中孔分子筛在气固色谱中的应用

将中孔分子筛这一新材料应用于气固色谱，可以分离脂肪烃，芳烃，卤代烃以及一些酮类化合物。对这种中孔分子筛柱的柱效，定量解吸等情况进行了考察，并与传统的气固色谱柱和一些常用气液色谱柱进行了对比。在填补中孔材料气固色谱吸附剂空白方面作了有意义的探讨。     

Interactions of some polar compounds with methylsilicone liquid phases in gas chromatography

Summary The changes in the heat of solution of polar compounds and xylene isomers in methylsilicone fluid OV-101 deposited on Chromosorb W AW DMCS were studied. It was shown that the heat of solution increases with an increase of the percentage loading of the OV-101 up to 10%. Solution and adsorption thermodynamic characteristics of the studied system are briefly discussed.     

Permethylated cyclodextrins in the GC separation of racemic mixtures of volatiles: Part 1

The chromatographic separation of racemic mixtures of volatile compounds by 2,3,6-trimethyl-α-, β- and γ-cyclodextrins is discussed. Columns were prepared by mixing the derivatized cyclodextrin with OV-1701 or hydroxy-terminated OV-1701 (OV-1701-OH) following Schurig's method [1]. About 130 racemates with widely differing structures were used to test the performances of 2,3,6-permethylated-α, β- and, γ-cyclodextrins mixed with the polysiloxane polymers in different ratios. The influence of the different types of cyclodextrin on racemate separation is shown, and some phenomena which might be helpful in the elucidation of the chromatographic behavior involved are also described. The influence both of the percentage of cyclodextrin in the polysiloxane, and of the operating conditions (carrier gas, flow rate, and temperature) in the separation of flavor and fragrance racemates is also evaluated.     

Behaviour of copper(II) and nickel(II) dialkyldithiocarbamates on polar and non-polar stationary phases

Summary Fifteen Dialkyldithiocarbamate complexes each of copper(II) and Ni(II) have been prepared and the retention times of these complexes have been measured on the non-polar OV-101 phase and the polar NGA and OV-225 phases. The relationship has been studied between the retention characteristics of the complexes and their structure. The lenght of the alkyl substituent, regarded as a steric hindrance, turned out to affect the retention of the complexes on the non-polar phases.

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Verhalten von Kupfer(II)- und Nickel(II)-dialkyldithiocarbamaten auf polaren und unpolaren stationären Phasen

Zusammenfassung Je 15 Dialkyldithiocarbamatkomplexe von Kupfer(II) und Nickel(II) wurden dargestellt und ihre Retentionszeiten auf der unpolaren Phase OV-101 sowie den polaren Phasen NGA und OV-225 gemessen. Die Beziehung zwischen der Retentionscharakteristik der Komplexe und ihrer Struktur wurde untersucht. Es zeigte sich, daß die Länge des Alkylsubstituenten (als sterische Hinderung) die Retention auf der unpolaren Phase beeinträchtigt.

     

联苯型高温液晶作气相色谱固定液的研究(Ⅰ)——菲、蒽和咔唑的分离

把高温液晶双-(对正烷氧基苯甲酸)-对-联苯二酚酯类(烷基为丙基、丁基、戊基、己基、庚基和壬基)作气相色谱固定液分离菲、蒽和咔唑.用半米色谱柱测定各个化合物的相对保留值.实验结果说明端基为丁烷氧基和戊烷氧基的液晶(BPBBB和BPBAmB)最好.在BPBAmB柱上16分钟内可满意地把菲、蒽和咔唑分离开.