Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Alkylbenzenes retention

Figure 2-12 represents the temperature dependencies of a homologous series of alkylbenzenes retention at 60% MeCN/40% water on a Phe-noemenex Luna-C18 column. The intercepts for each analyte is different from others, which essentially means that each analyte requires the determination of its own stationary phase volume. [Pg.50]

Figure 2-12. Temperature dependencies of alkylbenzenes retention at 60% MeCN/40 water on Luna-C18 column. Figure 2-12. Temperature dependencies of alkylbenzenes retention at 60% MeCN/40 water on Luna-C18 column.
The correlation between the retention and number of carbon atoms in a molecules can not be found. On Fig. 19 the dependence of the alkylbenzenes retention on hydroxylated silica from n-pentane on the number of carbon atoms of these molecules is presented from data of [26]. [Pg.698]

The e, f, g and h constants were determined so that the general empirical expression for the alkylbenzene retention factor with such microemulsion mobile phases could be expressed as ... [Pg.470]

Semiyen and Phillips applied their method of estimating log tj values to the results of Chang and Karr > for aromatic hydrocarbons which were measured on columns of 25% Apiezon L on firebrick at 150°C relative to n propylbenzene. Semiyen and Phillips used a value of 1,30 for the log t of benzene found by graphical extrapolation. Their alkylbenzene retention parameters had to be divided by 1.46 to give Chang and Karr parameters. [Pg.86]

Bentone-34 has commonly been used in packed columns (138—139). The retention indices of many benzene homologues on squalane have been determined (140). Gas chromatography of C —aromatic compounds using a Ucon B550X-coated capillary column is discussed in Reference 141. A variety of other separation media have also been used, including phthaUc acids (142), Hquid crystals (143), and Werner complexes (144). Gel permeation chromatography of alkylbenzenes and the separation of the Cg aromatics treated with zeofltes ate described in References 145—148. [Pg.424]

Tong and Tan [18] have performed a simultaneous determination of branched alkylbenzene sulfonates (ABSs) and LASs by HPLC using a C48 column. The elution of ABS produced one large wide peak representing the elution of the compounds with high molecular weight, with the same retention time of the CnLAS. [Pg.120]

Recent chromatographic data indicate that the interactions between the hydrophobic surface of a molded poly(styrene-co-divinylbenzene) monolith and solutes such as alkylbenzenes do not differ from those observed with beads under similar chromatographic conditions [67]. The average retention increase, which reflects the contribution of one methylene group to the overall retention of a particular solute, has a value of 1.42. This value is close to that published in the literature for typical polystyrene-based beads [115]. However, the efficiency of the monolithic polymer column is only about 13,000 plates/m for the isocratic separation of three alkylbenzenes. This value is much lower than the efficiencies of typical columns packed with small beads. [Pg.108]

The relationship of the selectivity towards rc-electrons can be understood from the differences in the retention factors of polycyclic aromatic hydrocarbons (Figure 3.13). The difference in the retention factors on end-capped and non-endcapped stationary phase materials is less than that of alkylbenzenes. This is due to the water content of the stationary phase. The content may be higher in non-endcapped bonded phases. [Pg.47]

Figure 4.1 Retention factors related to log P values. Column, 5/im octadecyl-bonded silica gel (LiChrosorb LC7) 25 cm x 4.1 mm i.d. eluent, 50% aqueous acetonitrile flow rate, 1ml min-1. Compounds , alkanols O, benzoates, O, polycyclic aromatic hydrocarbons, and A, alkylbenzenes. Figure 4.1 Retention factors related to log P values. Column, 5/im octadecyl-bonded silica gel (LiChrosorb LC7) 25 cm x 4.1 mm i.d. eluent, 50% aqueous acetonitrile flow rate, 1ml min-1. Compounds , alkanols O, benzoates, O, polycyclic aromatic hydrocarbons, and A, alkylbenzenes.
From the results in 40% aqueous THF and 50% aqueous acetonitrile (Figure 4.3B), the relative retention of PAHs (11-16) is weak and that of alkylbenzenes (O, 17-19) is strong in aqueous THF. The alkyl group affects the strong retention in aqueous THF. As found earlier (Table 4.3), a methanol-water... [Pg.63]

This method was applied to the prediction of the retention factor of phenols. First, this method requires a relationship between log A and the van der Waals volume of a homologous series of alkyl compounds such as alkylbenzenes or alkylphenones. When alkylbenzenes are used as the standard, the value of B in Equation 6.8 should be altered to give a parallel relationship at a suitable position (E) on the y-axis for a different group of compounds. When B is moved to E for phenols, the log A values of para-alkylated phenols (y) are simply predicted from their van der Waals volume by the following equation ... [Pg.127]

In extension, some retention index scales were proposed to mimic the Kovats index in GC. Alkanes, n-alkylbenzenes, alkan-2ones, alkylary] ketones, nitroalkanes, or polynuclear aromatic hydrocarbons were the advocated solutes. None of these scales is reliable, and observed indexes are not stable with variation in eluent composition, which precludes their use as a Kovats scale. [Pg.19]

It is evident from the data for monoalkylbenzenes on a-CD that the retention of n-alkylbenzenes is affected by the high stabilities of the complexes formed, caused by the location of the alkyl group in the cyclodextrin cavity. Branching of the side chain leads to a pronounced decrease in the retention. These results are similar those obtained for the interactions of n-alkanes and branched alkanes with a-CD (12.13). ... [Pg.250]

The experimental results with T-CD indicate (Table II) that the retention of substances examinated is not perceptibly affected by inclusion due to the large cavity of the cyclodextrin (14) Therefore, the retention data for all the p-isomers of dialkylbenzenes are lowest in contrast to the highest values for these derivatives on P-CD Among the disubstituted alkylbenzenes the o-isomers are retained most, owing to their more voluminous special... [Pg.251]

Among the alkylbenzenes, the stereospecific effect of liquid crystals is most marked in the separation of m- and p-xylene. The more linear p-xylene exhibiting a greater retention than the m-isomer (similar retention observed on a- and (3-CD). The retention order on the liquid crystals, m-< p-different from that on common polar and nonpolar stationary phases (p-< m-< o-isomer). In contrast to liquid crystals, o-xy-lene exhibited the lowest retention on a-CD. [Pg.252]

Expression (2-58) contains only the Gibbs free energies of the analyte interactions in the column and no eluent-related terms. This means that in ideal systems (in the absence of secondary equilibria effects) the eluent type or the eluent composition should not significantly influence the chromatographic selectivity. This effect could be illustrated from the retention dependencies of alkylbenzenes on a Phenoemenex Luna-C18 column analyzed at various ace-tonitrile/water eluent compositions (Figure 2-13, Table 2-2). [Pg.52]

Figure 2-13. Retention of alkylbenzenes on Luna-C18 column from acetonitrile/water eluent. Figure 2-13. Retention of alkylbenzenes on Luna-C18 column from acetonitrile/water eluent.
Figure 2-14. Retention of alkylbenzenes (benzene-octylbenzene) on Agilent Zorbax-Eclipse XDB C18 colnmn from different composition of acetonitrile/water eluent. Left pane Retention volumes right pane Retention factors. Figure 2-14. Retention of alkylbenzenes (benzene-octylbenzene) on Agilent Zorbax-Eclipse XDB C18 colnmn from different composition of acetonitrile/water eluent. Left pane Retention volumes right pane Retention factors.
Figure 4-7. Logarithm of the retention factor of alkylbenzenes on KovasU-C16 (non-porous silica) as a function of the acetonitrile content. Figure 4-7. Logarithm of the retention factor of alkylbenzenes on KovasU-C16 (non-porous silica) as a function of the acetonitrile content.
The main process determining analyte retention is the hydrophobic interactions with the stationary phase and its competition with organic mobile-phase additive. This simplistic description allows for a rough estimation of the analyte retention and, in principle, is applicable only for very ideal systems, like the separation of alkylbenzenes in methanol/water mixtures. [Pg.227]

Jinno, K. Kawasaki, K. Correlations between retention data of isomeric alkylbenzenes and physical parameters in reversed-phase micro high-performance liquid chromatography. Chromatographia 1983, 17 (6), 337-340. [Pg.1650]

Bernejo, I, Canga, J.S., Gayol, O.M. and Guillen, M.D. (1984). Utilization of Physicochemical Properties and Structural Parameters for Calculating Retention Indices of Alkylbenzenes. J.Chromatogr.ScL, 22,252. [Pg.538]

Dimov, N., Osman, A., Mekenyan, O. and Papazova, D. (1994). Selection of Molecular Descriptors Used in Quantitative Structure Gas Chromatographic Retention Relationships. 1. Application to Alkylbenzenes and Naphthalenes. Anal.Chim.Acta, 298,303-317. [Pg.558]

Heinzer, V.E.F. and Yunes, R.A. (1996). Using Topological Indices in the Prediction of Gas Chromatographic Retention Indices of Linear Alkylbenzene Isomers. J.Chromat., 719A, 462-467. [Pg.583]

Sutter, J.M., Peterson, T.A. and Jurs, P.C. (1997). Prediction of Gas Chromatographic Retention Indices of Alkylbenzene. Anal.Chim.Acta, 342,113-122. [Pg.650]

The adsorption from solutions of polycyclic aromatic hydrocarbons, alkylbenzenes and benzene derivatives is of great interest from many points of view. To understand the mechanism of their adsorption and to predict the equilibrium adsorption constant also it is possible to use the contributions of functional groups of fragments of molecules to retention in reversed-phase and normal-phase liquid chromatography [21]. The contributions of different molecular groups as well as the dependence of these contributions on mobile phase composition have been evaluated from experimental data in work [25]. [Pg.694]

The contributions of these groups to retention (a, values) evaluated from the retention of 38 alkylbenzenes on hydroxylated silica from n-pentane at room temperature [26] are presented on Table 8. [Pg.698]

The comparison of the experimental and the calculated In k values obtained by using the contributions to retention of different groups (Table 8) and the number of groups in a molecule is presented on Fig. 20. The calculated and experimental In k values are in a quite good agreement. Thus in the case of normal-phase chromatography it is possible to find the differences of contribution to the adsorption equilibrium constant of various functional groups of alkylbenzenes. [Pg.698]

Ivanciuc, O., Ivanciuc, T., Klein, D.J., Seitz, W.A. and Balaban, A.T. (2001d) Quantitative structure-retention relationships for gas chromatographic retention indices of alkylbenzenes with molecular graph descriptors. SAR e[ QSAR Environ. Res., 11, 419 52. [Pg.1077]


See other pages where Alkylbenzenes retention is mentioned: [Pg.43]    [Pg.30]    [Pg.150]    [Pg.187]    [Pg.208]    [Pg.47]    [Pg.409]    [Pg.192]    [Pg.400]    [Pg.225]    [Pg.253]    [Pg.373]    [Pg.523]    [Pg.248]    [Pg.698]   
See also in sourсe #XX -- [ Pg.50 , Pg.51 , Pg.52 , Pg.54 ]




SEARCH



Alkylbenzenes

Retention Time of Alkanes, Alkylbenzenes

© 2024 chempedia.info