Styrene-divinyl benzene based

The Separation of Some Phthalate Esters by Exclusion Chromatography on Styrene-Divinyl Benzene Based Gel... 

Polysaccharides Sephadex G-50, G-lOO, G-200, Bio-Gel P-6 P-100, styrene divinyl-benzene-based size-exclusion resins (e.g., Bio-Gel SEC), and their DEAE-bonded material... 

Most polymeric packings for size-exdusion diromatography in aqueous mobile phases are based on crosslinked glyddoxymethacrylate that is further hydrophilized and contains (—CH]—CHOH—CH2O— ) as the surface moiety. The exact composition, the nature of the crosslinker, the initiator, and the method of rendering the packings hydrophilic are all proprietary information that is not commonly disclosed by the manufacturers. But on the basis of studies available in die academic literature, one can surmise that the basic particle formation process is similar to the one described for styrene-divinyl-benzene-based packings. 

Styrene-based strong anion exchangers are obtained from a styrene-divinyl-benzene-based packing by chloromethylation followed by reaction with a tertiary amine. Weak anion exchangers are prepared throu the same route, but ammonia, primary, or secondary amines are used in the second step. 

Novolacs are often modified through alkylations based on reactions with monomers other than, and in addition to, aldehydes during their manufacture. Examples might be inclusion of styrene, divinyl benzene, dicyclopentadiene, drying oils, or various alcohols. Despite significant production of all of these variants, most novolac volume is produced using phenol and formaldehyde. 

The reaction is reversible and therefore the products should be removed from the reaction zone to improve conversion. The process was catalyzed by a commercially available poly(styrene-divinyl benzene) support, which played the dual role of catalyst and selective sorbent. The affinity of this resin was the highest for water, followed by ethanol, acetic acid, and finally ethyl acetate. The mathematical analysis was based on an equilibrium dispersive model where mass transfer resistances were neglected. Although many experiments were performed at different fed compositions, we will focus here on the one exhibiting the most complex behavior see Fig. 5. 

The majority of LC separations in CW analysis use stationary phases that separate analytes on the basis of hydrophobic interactions under reversed phase conditions, that is, they retain hydrophobic analytes more strongly than polar ones. The most commonly used stationary phases are based on 3-7 (commonly 3 or 5) micron-sized silica particles coated with bonded alkyl phases, or polymeric particles such as styrene-divinyl benzene copolymer. Bonded reversed phase silicas in decreasing order of hydrophobicity are Cl8 (ODS), octyl (C8), phenyl,... 

In reversed phase liquid chromatography (RPLC) silylated silicas are preferred. The surface of these silicas is covered with chemically bonded non-polar groups such as alkyl chains or polymeric layers (Chapter 3.2.3). Silica modified with medium polar groups such as cyano, diol or amino might be used in NP as well as RP mode. Alternatively, cross-linked polymers such as hydrophobic styrene divinyl benzene-copolymers can be used (Chapter 3.2.4). Polymer packings show stability in a pH range 2-14 while silica based packings show limited stability for pH > 7. 

We evaluated both gel and macroreticular types of styrene-divinyl-benzene (DVB) and acrylate-DVB strong base anion-exchange resins, all having quaternary ammonium groups attached to the polymer backbone. We used commercially available resins, specifically those of Rohm and Haas Amberlyst A-26, Amberlite IRA-400, Amberlyst XE-279, and Amberlite IRA-458 (all in the chloride form). The A-26 and IRA-400 resins contain styrene-DVB skeletal structures, with IRA-400 being a gel-type resin and A-26 the macroreticular resin. Resins IRA-458 and XE-279 contain acrylate-DVB skeletal structures, where IRA-458 is a gel-type resin and XE-279 a macroreticular resin. These studies compare the properties of the borohydride form of these resins with sodium and tetraethylammonium borohydride. 

A partial listing of available resins is given in Table 9. The Sepabeads adsorbents were introduced commercially in the mid 1980s (Mitsubushi Kasei) and were designed with a density of approx 1.2 g/L, achieved by bromination of the styrene divinyl benzene copolymer base matrix. A beneficial side effect of the bromination was that the surface hydrophobicity was increased relative to the naked polymer. In the case of P-lactam antibiotics such as cephalosporin C, the capacity was more than doubled from 25-50 g/L for the HP series (Mitsubushi Kasei Corp.) to 90-120g/L for Sepabeads. The Streamline adsorbents for proteins were introduced in 1993 (Pharmacia) and also feature a well-defined density of 1.2 g/L achieved by inclusion of an inert core material m the matrix. 

Fig. 8.6 Structure of sulfonic acid catalysts based on sulfonated styrene-divinyl benzene copolymers...

Nakagawa and co-workers [18] used techniques based on high resolution Py-GC and Py-GC and TGA to measure thermal degradation of chloromethyl substituted polystyrene. A typical TGA weight loss curve is shown in Figure 4.1. Degradation starts at 200 "C and peaks at 400 °C. Typical pyrolysis products of chloromethylated styrene-divinyl benzene (St-DVB) copolymers are the monomers, dimers and trimers of styrene, p-methyl styrene, and divinyl and ethyl styrene. For styrene chloromethyl St-DVB copolymers, in addition to the above, /-methyl styrene monomer and m- and p-chloromethyl styrene monomers are also present in pyrolysates. 

The resins are based on standard styrene/divinyl benzene polymers with weakly acidic functionality. The first resins developed borrowed directly from chelation (L. chela = claw) chemistry. Compounds such as ethylene diamine tetraacetic acid (EDTA) when ionized have two monovalent anionic end groups that do in fact have a claw-like structure. They have a powerful affinity for divalent cations such as calcium and magnesium. When iminodiacetate functionality is built into a polymer, it provides... 

Figure 3.129 Separation of halide ions with a tyrosine eluent on a poly(styrene-co-divinyl-benzene)-based anion exchanger. Separator column lonPac AS4A-SC eluent 1 mmol/L tyrosine + 3 mmol/L NaOH flow rate 2 mL/...

Other widely used ion-exclusion columns for the analysis of organic acids in combination with carbohydrates and alcohols are Aminex HPX-87 H (Bio-Rad, Hercules, CA, USA) and Rezex ROA (Phenomenex, Torrance, CA, USA), which are typically operated at elevated temperatures for optimal resolution. Both column substrates are totally sidfonated poly(styrene-co-divinyl-benzene)-based resins with a degree of cross-linking of 8% that slightly differ in particle size. Figure 5.7 illustrates the better resolution and peak shapes with less fronting effects for organic acid analysis on the Rezex ROA colunrn in comparison to the Aminex HPX-87H, while the overall analysis times are comparable. 

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