Capillary complexation gas chromatography in analysis of halohydrocarbons

Summary Investigations were carried out on capillary columns coated with liquid stationary phases possessing cyano (3-cyanopropylmethylpolysiloxane) and thiol (3-mercaptopropylmethylpolysiloxane) groups. These phases were modified by bonding CuCl₂ and CoCl₂ to cyano groups or NiCl₂ and CoCl₂ to thiol groups. The modified phases were examined in order to assess their usefulness for the analysis of aliphatic and aromatic halohydrocarbons. A number of retention parameters (I, ΔMe, Vg), which allow characterisation of the specific interactions between the bonded metal and the halohydrocarbon molecule, were determined for the columns both with and without the metal. The separations performed show that the columns with bonded metals are applicable for the practical analysis of the halohydrocarbons.     

Interpretation of interactions of halogenated hydrocarbons with modified silica adsorbent coated with 3-benzylketoimine group silane

The paper reports a new group of adsorbents obtained by modification of silica surface with silane containing 3-benzylketoimine groups with bonded Cu(II) and Ni(II) chlorides. The adsorbents obtained were subjected to a chromatographic study to establish the type of adsorbate-adsorbent interactions for aliphatic and aromatic halogenated hydrocarbons used as adsorbates. The following retention parameters were determined: retention factor (k), Kovats retention index (I), specific retention volume (V _g), and molecular retention index (ΔM _e). Values of the molecular retention index were subjected to complex statistical analysis providing qualitative relations between the adsorbates’ properties and spatial structure and their retention. It was observed that bonding of chlorides of Cu(II) and Ni(II) with the ketoimine groups resulted in an increase of the retention index and the molecular retention index indicating an increase of the adsorbate-adsorbent interaction in comparison with the reference column coated with silane including a 3-benzylketoimine group without transition metal chlorides. Along with the observed increase of the adsorbate-adsorbent interaction, larger difference between the retention indices was observed for both halogenated compounds. This indicates a positive influence of the introduced transition metals on the selectivity of the adsorbate-adsorbent interactions of the examined columns.     

Heterocyclization of dimethyl malonate with SH acids and formaldehyde in the presence of catalysts

Three-component heterocyclization of dimethyl malonate with SH acids (H₂S, ethane-1,2-dithiol) and formaldehyde in the presence of 5 mol % of transition metal chlorides (FeCl₃, CoCl₂, NiCl₂) gave dimethyl 1,3-dithiane-5,5-dicarboxylate and dimethyl 1,4-dithiepane-6,6-dicarboxylate. The reactions in the presence of transition metal chlorides hydrates were accompanied by Krapcho decarboxylation with formation of methyl 1,3-dithiane-5-carboxylate and methyl 1,4-dithiepane-6-carboxylate.     

Capillary complexation gas chromatography in analysis of cyclic and aromatic hydrocarbons

Summary Results of studies on stationary phases containing copper(II), nickel(II) and cobalt(II) chloride chemically bonded via cyano—or thiol groups are presented. The retention parameters—i.e. retention factor (k), retention index (I) and molecular retention index (ΔMe) and specific retention volume (Vg)-enabled the characteristics of specific interaction between aromatic and cyclic hydrocarbons and metal complexes chemically bonded to stationary phases to be determined. Presented at Balaton Symposium on High Performance Separation Methods, Siófok, Hungary, September 1–3, 1999     

金属离子在液相氧化中的催化作用——Ⅹ.过渡金属氯化物与简单配体原位形成的配合物在环己烯氧化反应中的催化作用

本文研究了由过渡金属氯化物(MnCl₂、FeCl₂、CoCl₂、CuCl)与2,2′-二吡啶原位形成的配合物,在环己烯氧化反应中的催化性能以及配体性质对所形成的配合物催化性能的影响.结果表明,多种过渡金属氯化物可与2,2′-二吡啶原位形成有催化活性的配合物,其催化活性与金属离子性质、形成配合物能力以及配体性质有关.     

Separation of Dietary Folates by Gradient Reversed-Phase HPLC: Comparison of Alternative and Conventional Silica-Based Stationary Phases

A study of ten silica-based stationary phases and gradient elution conditions to separate dietary folates by reversed-phase HPLC was performed. Alkyl-bonded stationary phases (both conventional and alternative) were found to be the most promising for the separation of different folate monoglutamates in terms of selectivity and peak shape. These phases were better than phenyl-bonded phases which lacked selectivity when separating 10-formyl-folic acid and 5-formyl-tetrahydrofolate. Polar-bonded (cyano) stationary phase showed similar retention characteristics as the conventional alkyl-bonded phases, but ranked below those in terms of peak shape. Overall, alternative stationary phases exhibited slightly higher retention of late-eluted folates and greater retention variability for early-eluting tetrahydrofolate and 5-methyl-tetrahydrofolate. Best selectivity was achieved on alternative polar endcapped Aquasil C₁₈ followed by conventional Synergy MAX C₁₂ and Genesis C₁₈ stationary phases.     

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).     

Retention characteristics of aliphatic compounds on cellulose acetates as a stationary phase with an aqueous mobile phase

Summary Cellulose and cellulose mono-, di-, and triacetate were used as stationary phases for liquid chromatography with water as a mobile phase, and the retention behavior of alcohols, ethers, ketones, and chlorides was examined. For cellulose acetate columns, the logarithm of the specific retention volume, (logV _g ^* ), correlated linearly with the logarithm of partition coefficient between 1-octanol and water (log K_o/w), for each homologous group, but all solutes were unretained on cellulose columns. With the exception of chlorides, the intercept values of the log V _g ^* –log K_o/w regression lines increased significantly with increase of acetyl content of cellulose acetates, but the slopes of the regression lines changed little. This suggests that hydrophobic interaction between the acetyl groups of cellulose acetates and the alkyl chains of the solutes is the dominant factor in the retention.The capacity factors for 1-alcohols with cellulos diacetate column indicated a maximum at a column temperature of about 40°C. This unique retention behavior was assumed to be caused by small structural change of the cellulose acetate polymer, because this temperature effect on the retention corresponded with effects observed by differential scanning calorimetry (DSC).     

The correlation between the physical properties and structure of alcohols and their gas chromatographic behavior on polar and non-polar stationary phases : II. Branched-chain alcohols

Branched-chain alcohols with from one to eight carbon atoms have been analysed by gas chromatography using thermal conductivity and flame-ionization detectors. The specific retention volumes, V_g, and the retention indices relative to normal alcohols were determined for all the compounds, and the effects of the branching and of the position of the hydroxyl groups have been investigated. Boiling points, vapour pressures, molecular volumes were correlated with the measured retention values. The activity coefficients at infinite dilution and the normalized activity coefficients were calculated, and their influence on the separation is discussed. The results are compared with the behaviour of branched-chain halogenoalkanes on polar and non-polar stationary phases.     

The Choice of Polar Stationary Phases for Gas–Liquid Chromatography by Statistical Analysis of Retention Data

We have studied the retention indices of 127 volatile substances on a C₇₈-paraffin and on its seven nearly isochor and isomorphous polar derivatives over a temperature range of 90–210 °C. The retention index of a substance on the C₇₈ paraffin has been considered as the standard. The additional retention on the polar derivative was given by the difference of its retention index on the polar solvent and on the C₇₈-paraffin. Statistical analyses of the additional retention have shown that with respect to retention, the seven polar solvents can be classified into three groups: Type I: TTF (tetrakistrifluoromethyl), MTF (monotrifluoromethyl), Type II: PCN (primary cyano), PSH (primary thiol) and Type III: TMO (tetramethoxy), SOH (secondary alcohol) and POH (primary alcohol). It is shown that these three types are best represented by the solvents TTF, PCN and TMO. PSH (primary thiol) is aligned with PCN at temperatures up to about 150 °C, but is similar to TMO at 210 °C.     

Isomeric structure of styrene-acrylonitrile and styrene-methylcrylate copolymer pyrolysis products

Summary Gas chromatographic retention indices of pyrolysis products of styrene-acrylonitrile and styrene-methylacrylate copolymers were measured on two columns prepared with different stationary phases. A retention index against retention index diagram proved to be useful to define the composition of product molecules, as the points of homologous series form straight lines. We identified the isomeric structure of dimers and trimers consisting of two kind of monomer units by comparing their retention indices. This comparison was based on the determination of the retention index increments of cyano, methoxy-carbonyl and phenyl groups bounded to primary, secondary or olefinic carbon atom. The isomeric structures of styrene-acrylonitrile dimers and trimers were confirmed by mass spectroscopy.     

Cyclam complexes of Cu(II) and Co(II) as stationary phases for gas chromatography

New macrocyclic stationary chemically bonded phases were synthesized and tested in gas chromatography conditions. The complexes of 1,4,8,11-tetraazacyclotetradecane with Cu(II) and Co(II) were bonded to the silica support through the (3-chloropropyl)triethoxysilane reactant. The packings obtained were analyzed by diffuse-reflectance ultraviolet–visible spectroscopy (DRUV–Vis), differential thermal gravimetry (DTG), porosimetry, and elementary analysis. Preliminary study of the novel silica gas chromatography (GC) stationary phases containing cyclam complexes was carried out using packed 1/8 in. i.d. columns. The study was conducted on: cyclic, linear and branched olefins, aromatic hydrocarbons and ethers. Characterization of interactions between the compounds mentioned and new stationary phases was based upon analysis of Kováts retention indices (I), difference between retention indices for two phases (ΔI), and molecular retention indices (ΔM_e). Results have shown that the new stationary phases interact sufficiently strongly with molecules of high electron density and can be applied in capillary gas chromatography for the analysis of light hydrocarbons.     

Measurement of Henry coefficients by capillary columns coated with slightly polar solvents

Summary The specific retention volumes and Henry coefficients measured on packed columns are compared with those calculated via retention indices determined on wall coated open tubular capillary columns. The stationary phase liquids used were derivatives of a branched paraffin, C₇₈H₁₅₈, where a methyl or ethyl group of the paraffin was replaced by OH, CN, OCH₃ and SH groups. The retention indices of a series of molecular probes of varying polarity (aromatics, 1-chloroalkanes, 1-acetoxy-alkanes, 1-alkanols, 2-alkanones) were determined atT=403.15 K on fused-silica open tubular columns prepared by static coating that gave stable and uniform solvent films. After obtaining the absolute data on packed columns forn-alkanes, the specific retention volumes and Henry coefficients of the solutes were calculated. The retention data obtained on both columns showed good agreement. Presented at Balaton Symposium on High Performance Separation Methods, Siófok, Hungary, September 1–3, 1999     

Interactions between metal chlorides and poly(vinyl pyrrolidone) in concentrated solutionsand solid‐state films

The rheological behavior of poly(vinyl pyrrolidone) (PVP)/N,N‐dimethylformamide (DMF) solutions containing metal chlorides (LiCl, CaCl₂, and CoCl₂) were investigated, and the results showed that the nature of the metal ions and their concentration had an obvious effect on the steady‐state rheological behavior of PVP–DMF solutions with different molecular weights. The apparent viscosity of the PVP–DMF solutions increased with an increasing metal‐ion concentration, and the viscosity increment was dependent on the metal‐ion variety_. For a CaCl₂‐containing PVP–DMF solution, for example, the critical shear rate at the onset of shear thinning became smaller with increasing CaCl₂ concentration. It was believed that multiple interactions among metal ions, carbonyl groups of PVP, and amide groups in DMF determined the solution properties of these complex fluids; therefore, ¹³C NMR spectroscopy was used to detect the interactions in systems of PVP–CaCl₂–DMF and PVP–LiCl–DMF solutions. NMR data showed that there were obvious interactions between the metal ions and the carbonyl groups of the PVP segments in the DMF solutions. Furthermore, IR spectra of the PVP/metal chloride composites demonstrated that the interaction between the metal ions and carbonyl groups in the PVP unit occurred and that the PVP chain underwent conformational variations with the metal‐ion concentration. DSC results indicated that the glass transition temperatures of the PVP/metal chloride composites increased with the addition of metal ions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1589–1598, 2007     

Co (II)‐C12 alkyl carbon chain multi‐functional ionic liquid immobilized on nano‐SiO2 nano‐SiO2@CoCl3‐C12IL as an efficient cooperative catalyst for C–H activation by direct acylation of aryl halides with aldehydes

Nano‐silica supported ionic liquids composed of alkyl carbon chain and transition metal chlorides anions have been prepared and successfully applied as a heterogeneous catalyst in the direct aldehyde C‐H activation. Catalytic results indicated that nano‐SiO₂ supported ionic liquid consisting C12 alkyl carbon chain and CoCl₃ anion nano‐SiO₂@CoCl₃‐C12IL showed excellent catalytic properties with good to excellent yields towards the desired aryl ketones. The excellent recyclability of the supported catalyst, mild reaction conditions, low catalyst loading, and operational simplicity are the important features of this methodology.     

Comparative evaluation of retention of hydrocarbons present in the C5-petroleum fraction on methylsilicone and squalane phases

Summary The retention of hydrocarbons present in the C₅ pyrolysis fraction of gasolines on the stationary phases squalane and methylsilicone oil JXR at 30, 40 and 50°C was investigated by capillary gas chromatography. The unified retention indices of the hydrocarbons were also calculated on squalane. The retention indices obtained on these two phases were interrelated and the quantitative relationship with the structure of the solutes was studied. Equations based on the unified retention indices calculated on squalane and some selected structural elements of the solutes permit the calculation of their retention on methylsilicone with sufficient accuracy.     

A Comparison of the Retention Behaviour of Vitamin A and Some Metabolites Eluted from Four Different Reversed Phase High Performance Liquid Chromatographic Stationary Phases

Five retinoids, 13-cis-retinoic acid, 9-cis-retinoic acid, all-trans-retinoic acid, all-trans-retinol and 13-cis-retinal were isocratically separated from four different reversed phase high performance liquid chromatographic stationary phases. By taking advantage of the different retention mechanisms, present between the stationary phases and the analytes, the retinoids were separated with different elution orders using the same mobile phase composition. Two of the stationary phases appeared to have more possibilities to interact with the analytes than the usual hydrophobic interactions. The stationary phase with embedded polar groups showed hydrogen bonding properties and the calix[4]arene based stationary phase showed possibilities to form inclusion complexes with the analytes. These additional interactions appeared to benefit the separations of the analytes. This publication shows the benefits by isocratically separate retinoids employing other stationary phases than the conventional C₁₈ stationary phase.     

Gas chromatographic retention indices for C6 alkanols on OV-101 and Carbowax 20M capillary columns

Summary Gas chromatographic retention indices for 16 C₆ alkanols measured on capillary columns coated with OV-101 methylsilicone and Carbowax 20M propylethyleneglycol liquid phases at 80° and 90°C were determined. The respective standard deviation values were 0.5 and 0.8 i.u. The correlation between the retention indices measured on non-polar and polar stationary phases and the boiling points of the alkanols was studied.     

Metal exchange reactions between cadmium protoporphyrin and cobalt and zinc chlorides in acetonitrile and dimethyl sulfoxide

Metal exchange between cadmium protoporphyrin CdPP and zinc and cobalt chlorides in dimethyl sulfoxide (DMSO) and acetonitrile (AN) was studied by spectrophotometry. Comparative analysis of the data on metal exchange between CdPP and ZnCl₂ in DMSO and between CdPP and CoCl₂ in AN was performed. The possible exchange mechanisms were considered. The results were compared with the data on cadmium mesoporphyrin exchange with zinc and cobalt.