Normal phase aromatic hydrocarbons

However, ia some cases, the answer is not clear. A variety of factors need to be taken iato consideration before a clear choice emerges. Eor example, UOP s Molex and IsoSiv processes are used to separate normal paraffins from non-normals and aromatics ia feedstocks containing C —C2Q hydrocarbons, and both processes use molecular sieve adsorbents. However, Molex operates ia simulated moving-bed mode ia Hquid phase, and IsoSiv operates ia gas phase, with temperature swiag desorption by a displacement fluid. The foUowiag comparison of UOP s Molex and IsoSiv processes iadicates some of the primary factors that are often used ia decision making ... 

Polymerization of triphenylmethyl methacrylate in the presence of a chiral anion catalyst results in a polymer with a helical structure that can be coated onto macroporous silica [742,804). Enantioselectivity in this case results from insertion and fitting of the analyte into the helical cavity. Aromatic compounds and molecules with a rigid nonplanar structure are often well resolved on this phase. The triphenylmethyl methacrylate polymers are normally used with eluents containing methanol or mixtures of hexane and 2-propanol. The polymers are soluble in aromatic hydrocarbons, chlorinated hydrocarbons and tetrahydrofuran which, therefore, are not suitable eluents. 

The -modification as a rule evolves as a more coarse-grained material than the a-phase. It is prepared by milling the crude Copper Phthalocyanine Blue with salt in the presence of a crystallization stimulating solvent. Aromatic hydrocarbons, esters, or ketones are normally used. 

Gustavson, K.E. DeVita, W. Revis, A. Harkin, J.M. 2000, A novel use of a dual-zone restricted access sorbent Normal phase separations of methyl oleate and polynuclear aromatic hydrocarbons stemming from semipermeable membrane devices. J. Chromatogr. A 883 143-149. 

Analytical Properties Separations via interactions with n-electrons of solutes can be used in both normal and reverse phase for such n-donor systems as polynuclear aromatic hydrocarbons Reference 33... 

Analytical Properties Separates aromatic and polynuclear aromatic hydrocarbons can be used in normal phase mode (commonly using n-heptane or n-heptane + dichloromethane liquid phases) or reverse phase mode (commonly using methanol + water, acetonitrile + water, or phosphate-buffered liquid phases) Reference 45... 

FIGURE 4-4. Two approaches to the separation of polynuclear aromatics, (a) Reverse-phase separation of isomeric 4-ring polynuclear aromatics using a gradient of 70/30 (v/v) to 100/0 (v/v) acetonitrile/water as shown beneath the chromatogram. Column C,g detection at 254 nm. (b) Normal-phase separation of aromatic hydrocarbons. Column /uPorasil (silica, 10 /urn) 3.9 mm ID x 30 cm (2 columns) mobile phase hexane flow rate 8 mL/min. (Fig. 4-4b reproduced from reference 1 with permission.)... 

Homoaerothionin, biosynthesis of 1315, 1316 HomocaUxarenes, synthesis of 1376-1381 Homoerysodienones, formation of 1297 B-Homoerythrina alkaloids 1297 synthesis of 1300 Honey, analysis of 961, 973 Horseradish peroxidase 974, 977, 978, 981 as oxidation catalyst 1216, 1217, 1219-1221, 1224, 1225 HPLC, normal phase 953 H-point standard additions method 954 HSZ-360 catalyst 680 Hydrocarbons, aromatic,... 

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]. 

This phase is selective for aromatics and its effectiveness is demonstrated in Figure 11.5. Normal coal-tar pitch (residue from commercial high-temperature coal tar distillation) was analysed and around 90 components could be distinguished, including polycyclic aromatic hydrocarbons and related heterocyclic and oligomer systems. Twenty-four of these were clearly identified by their characteristic UV spectra and comparison with known reference spectra. 

The extraction of aromatic hydrocarbons (Fig. 5.5) from crude oil uses two sorbents in series, first a cyanopropyl column attached to a second silica column. In this procedure, aromatic hydrocarbons are sorbed on both the cyanopropyl sorbent and on the silica sorbent. The heteroatom hydrocarbons (containing nitrogen, oxygen, and sulfur) are trapped on the cyanopropyl sorbent and eluted as a separate fraction from the silica column. Because the major interaction of aromatic heterocyclic hydrocarbons is through hydrogen bonding to the surface of the sorbent, the cyanopropyl sorbent is easier to elute than a silica sorbent alone. For this reason, the cyanopropyl column is used before the silica column. The separation of hydrocarbons from crude oil is an example of normal-phase chromatography that has been performed for many years on silica gel prior to the introduction of SPE. 

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