Packed columns porous polymer

The chromatographic procedure may be performed using a glass column (1.5 x 4 mm) packed with porous polymer beads (80 to 100 mesh) e.g., Porapack-Q and maintained at 140°C. 

Column Stainless steel size (1 M x 2 mm) adsorbent packed with porous polymer beads (60 to 80 mesh) and maintained at 120 °C. 

GPC is a further special form of liquid chromatography. The separation column is packed with porous, polymer gels (e.g. polystyrene gel) as stationary phase. The particle size of the packing material and the size distribution of the pores are well defined and uniform. In GPC molecules are separated according to their effective size in solution, i.e., their hydrodynamic volume, and not according to their affinity for the support material. 

Alternative sorbents for the collection of polar organic compounds which are sensitive to hydrolysis are porous polymers such as the Chromosorb porous polymer column packings, Porapak porous polymer column packings, Tenax-GC column packing, and Amberlite XAD sorbent products. XAD-2 resin has been used for a number of compounds and, for example, has been shown valuable for the... 

As already outiined in Sections 3.4.1.6 and 3.12.2, monolithic separation media have made a significant impact on separation science because of the advantages they offer over packed columns. Polymeric monoliths consist of a single piece of highly porous material that does not contain interparticular voids typical of packed beds. Porous polymer monoliths are successfiilly used for the separation of biomolecules such as peptides and proteins for more than 10 years. The... 

HOPC uses a column packed with porous materials that have a pore diameter close to a dimension of the solvated polymer to separate. A concentrated solution of the polymer is injected into the solvent-imbibed column by a high-pressure liquid pump until the polymer is detected at the column outlet. The injection is then switched to the pure solvent, and the eluent is fractionated. A schematic of an HOPC system is illustrated in Fig. 23.1. A large volume injection of a concentrated solution makes HOPC different from conventional SEC. 

A narrow pore size distribution is essential to HOPC. To separate polymer samples with various average molecular weights, users need to prepare columns packed with porous materials of a uniform but different pore size, e.g., 10, 13, 18, and 24 nm. In contrast, a broader pore size distribution is common in a SEC column. A need to analyze a wide range of molecular weights (over many decades) by a single set of columns has spread the use of these columns. 

Various types of porous polymers have also been developed as column packing material for gas chromatography, e.g. the Porapak series (Waters Associates) and the Chromosorb series (Johns Manville) which are styrene... 

Catechin-immobilizing polymer particles were prepared by laccase-catalyzed oxidation of catechin in the presence of amine-containing porous polymer particles. The resulting particles showed good scavenging activity toward stable free l,l-diphenyl-2-picryl-hydrazyl radical and 2,2 -azinobis(3-ethylbenzothiazoline-6-sulfonate) radical cation. These particles may be applied for packed column systems to remove radical species such as reactive oxygen closely related to various diseases. 

The porous glass packed columns did not yield high resolution separations, but the major species present in a latex were adequately separated. Figure 1. Insoluble polymer, when present, was excluded from the pores and eluted at interstitial volume. Elution order of remaining species was soluble polymer, unreacted monomers, and water. In both types of resins studied, no separation of the two unreacted monomers was achieved. A single chromatographic peak, that included both monomers, was obtained. 

Donovan and Pescatore described another fast-gradient approach with very short columns (20x4.6 mm internal diameter) packed with a porous polymer (known as ODP columns) [38]. This chromatographic support presents a high chemical stability and can be used at pH 2, 10 or 13 to analyze neutral analytes. This procedure allowed a relatively high flow rate (2mLmin ) and a gradient from 10 to 100% methanol in only 7 min. The mathematical treatment was simplified and based on the direct transformation of retention time to log P. For this purpose, two standards (toluene and triphenylene) were used to minimize retention time variations from run-to-run and instrument-to-instrument, and to facilitate the... 

Current research in CEC involves the use of monolith capillaries, which are fritless, packed capillaries having stationary phase bound to the capillary wall. Using porous polymer monoliths, the retention of a packed column can be found in an open tubular capillary. In general, CEC remains unsettled. Frit technology is unreliable and research into monolithic capillaries is still a work in progress. Recent progress in CEC can be found in the reviews by Colon and co-workers. 

An open-tubular column is a capillary bonded with a wall-supported stationary phase that can be a coated polymer, bonded molecular monolayer, or a synthesized porous layer network. The inner diameters of open-tubular CEC columns should be less than 25 pm that is less than the inner diameters of packed columns. The surface area of fused silica tubing is much less than that of porous packing materials. As a result, the phase ratio and, hence, the sample capacity for open-tubular columns are much less than those for packed columns. The small sample capacity makes it difficult to detect trace analytes. 

FIGURE 16.3 Dependences of the polymer retention volume on the logarithm of its molar mass M or hydrodynamic volume log M [T ] (Section 16.2.2). (a) Idealized dependence with a long linear part in absence of enthalpic interactions. Vq is the interstitial volume in the column packed with porous particles, is the total volume of liquid in the column and is the excluded molar mass, (b) log M vs. dependences for the polymer HPLC systems, in which the enthalpic interaction between macromolecules and column packing exceed entropic (exclusion) effects (1-3). Fully retained polymer molar masses are marked with an empty circle. For comparison, the ideal SEC dependence (Figure 16.3a) is shown (4). (c) log M vs. dependences for the polymer HPLC systems, in which the enthalpic interactions are present but the exclusion effects dominate (1), or in which the full (2) or partial (3,4) compensation of enthalpy and entropy appears. For comparison, the ideal SEC dependence (Figure 16.3a) is shown (5). (d) log M vs. dependences for the polymer HPLC systems, in which the enthalpic interactions affect the exclusion based courses. This leads to the enthalpy assisted SEC behavior especially in the vicinity of For comparison, the ideal SEC dependence (Eigure 16.3a) is shown (4). 

The effect of exclusion on the retention volumes of macromolecules was qualitatively explained above. The pioneering work of Casassa [54] has shown that the extent of pore exclusion of macromolecules is controlled by the changes in their (conformational) entropy. The principle is explained in a simplified form in Figure 16.4a through c. A zone of polymer solution with a nonzero concentration travels along a column packed with porous particles. Initially, the concentration of macromolecules within pores is zero (Figure 16.4a). The concentration gradient outside of pore (c > 0) and within pore (c = 0) pulls macromolecules into the pores. 

Waste gas is first drawn in through the air/water separator, used to remove impurities in the air such as water droplets, solid particles, etc. The effluent then travels to the trickling filter, which is a packed column of very porous polymer material. The use of a polymer as the packing material enhances mass transfers between the liquid and gas. The polymer can fix a large culmre of specific bacteria capable of degrading contaminants found in the liquid phase. The trickling filter is followed by a compost-based biofilter that removes residual contaminants. 

As the name implies, GPC or SEC separates the polymer according to size or hydrodynamic radius. This is accomplished by injecting a small amount of (100-400 fi 1) of polymer solution (0.01-0.6%) into a set of columns that are packed with porous beads. Smaller molecules can penetrate the pores and are therefore retained to a greater extent than the larger molecules which continue down the columns and elute faster. This process is illustrated in Figure 4. 

The porous polymer stationary phases which for many years have been available in packed gas chromatography columns has only recently become available as a coated capillary [24]. These cross-linked porous polymer columns are produced by copolymerizing styrene and divinylbenzene. The pore size and surface are varied by altering the amount of divinylbenzene added to the polymer. These PLOT capillary columns exhibit the same separative characteristics as Poropak Q packed columns. 

Solvent residues - Gas -chromatography on various porous polymer packed columns [679]... 

In addition to utilization of monoliths as a column material, two reports describing respectively silicate and synthetic organic polymer based monolithic frits were published recently [85,86], The conventional method of frit fabrication for a particle packed column usually involves thermal sintering of a section of the packing material, such as bare or octadecyl silica, using a heating device. This approach has several weaknesses such as the lack of control of the temperature and porous properties of the frit that decreases reproducibly of the fabrication process. 

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