Polymer Packings Research Articles

Microcolumn size exclusion chromatography with polymeric stationary phases

Miniaturization of the column used in liquid chromatographic separations to microcolumn dimensions (0.1-0.5-mm i.d.) offers various advantages to the technique, such as low eluent consumption, ability to interface to other chromatographic techniques and mass spectrometers, low cost per column, and reduced maintenance requirements, among others. This report documents studies conducted in the preparation of highly efficient microcolumns for size exclusion chromatography (micro SEC) with polymer packings of 50- and 1000-A pore size

Characterization of Spherical Polymer Packings fromN,N-Dialkyl Acrylamide for Reversed-Phase Liquid Chromatography

Abstract Chemically stable and totally organic polymer packings were prepared using N,N-dialkyl acrylamide monomers and their chromatographic properties were investigated. The hydrophobic parts of polymer packings were composed of N-methyl N-octadecyl acrylamide and N,N'-dibutylhexane N,N'-diacrylamide was used as a crosslinking monomer. The hydrophobicity of the spherical particles was easily controlled varying by the monomer ratio in the suspension polymerization. As for RPLC behavior, the packings had no abnormal adsorption for ionic substances and showed no excessive retention and no peak tailing for carbonyl compounds, because the packings had no ionic groups or amide protons. In addition, the packings show better alkali-and acid-resistances than conventional polymer packings into which alkyl groups were introduced through ester bondings.

Verification of nonproduction of chemical warfare agents: I. Determination of organophosphorus compounds by microcolumn liquid chromatography with flame photometric or thermionic detection

AbstractMicrocolumn liquid chromatography (micro‐LC) with on‐line flame photometric (FPD) or thermionic detection (TID) has been used for the determination of a series of organophosphoric and organophosphonic acids isolated from various sample matrices. Silica‐based ion‐exchange materials and polymer packings have been used as stationary phases. In order to improve the sensitivity (expressed in concentration units) of the technique, trace enrichment via a miniaturized precolumn (4 mm × 1 mm i.d.) and direct large‐volume injections (1–10 μL) of aqueous samples have been studied. As an application, the verification of nonproduction of chemical warfare agents and their alleged use have been investigated by analyzing their hydrolysis products in spiked surface water and soil samples. The application of both the precolumn technique and large‐volume injections permit the detection of organophosphorus acids in water and soil at the low ppm level.

Isocratic HPLC separation of aromatic hydrocarbons and fluorine-containing compounds using perfluoroalkyl polymer packings

Porous, perfluoroalkylated polymer-gels for column packings in high-performance liquid chromatography (HPLC) were prepared by suspension polymerization of heptadecafluorodecyl arcylate and ethylene glycol dimethacrylate. The packings showed no abnormal retention for ionic or aromatic compounds, due to the lack of ionic or aromatic groups. In addition, the packings showed no excessive retention for strongly hydrophobic compounds which is often the case with long-chain, alkylated silica gels and polymer gels. This is due to the extremely low surface energy of perfluoroalkyl groups. Therefore, perfluoroalkylated polymer gels enable isocratic HPLC separation of solutes with significantly different hydrophobicity.

Porous polymer packings from vinyl ether derivatives for reversed-phase liquid chromatography

Spherical, porous-polymer particles for column packing in high-performance liquid chromatography were prepared by suspension copolymerization of alkylvinyl ether with triethyleneglycol divinyl ether. The hydrophobicity of the packings was easily adjusted by changing the monomer ratio. The packings showed the usual reversed-phase liquid chromatographic properties, but did not sho abnormal retention, tailing and broadening of peaks and irreversible adsorption of ionic and aromatic substances, owing to the lack of ionic or aromatic groups. In addition, the packings were stable in alkaline solutions because of the relative alkali stability of C−O−C bonds as compared with CO−O and Si−O−C bonds in conventional packings.

Development of Macroporous Polymer Packings for Aqueous High Flow Rate Liquid Chromatography. Approach on the Viewpoint of Materials Chemistry

Gel production methods have recently been improved, and a systematic search for packing materials has led to the creation of various hard particles from hydrophilic condensation polymers, making it possible for aqueous gel permeation chromatographic separation to occur at higher flow rates. In the present review, we explain the production methods, efficiency, and applications of hydrophilic packings developed due to this improvement in packing materials, while especially emphasizing their hardness.

Preliminary results on the gas chromatographic evaluation of interpenetrating polymer networks prepared from porous polymer beads

This paper proposes a novel chemical derivatization technique as a means of changing the chromatographic behaviour of some porous polymer packings by producing a structure defined as an interpenetrating polymer network. This kind of derivatization may also be helpful for changing the hydrophobic properties of polymer packings and for reducing their swelling inorganic solvents

Size-dependent, chromatographic separation of double-stranded DNA which is not based on gel permeation mode

A new procedure for size-dependent fractionation of DNA was investigated. DNA fragments ranging from 10 to 40 kbp were separated by using columns for high-performance gel permeation chromatography. However, the order of elution was opposite to that which would be expected for gel permeation chromatography, i.e., smaller fragments were eluted faster than larger fragments, though separation based on normal gel permeation chromatography was observed when smaller DNA fragments (less than 5 kbp) were applied. The size range of DNA which can be resolved by this new procedure was found to depend on both particle size and flow rate; the use of a column packed with smaller particles or the application of a faster flow rate enabled us to resolve smaller DNA fragments, but the pore size or chemical nature of the column packing had scarcely any effect on the resolution. This mode of separation was attained by using both silica and polymer packings. The results suggest that the separation is based on a hydrodynamic phenomenon.

Quantitative analysis of 68 polar compounds from ten chemical classes by direct aqueous injection gas chromatography

Porous polymer packings have been used successfully in many applications of direct aqueous injection gas chromatography. We have expanded the use of aqueous injection to the quantitative analysis of 68 alcohols, acetates, ketones, ethers, sulfides, aldehydes, diols, diones, nitriles and amides on a glass column packed with unmodified tenax GC using a flame-ionization detector. Analysis of single- and multicomponent mixtures, accurate standard preparation, assessment of analytical errors, limitations of the method and problems encountered are discussed. Peak ghosting and tailing were not serious problems. The analytical error between chemical classes expressed as the coefficient of variation between duplicate samples ranged from 0.81 % for nitriles ( n  3) to 7.09 % for ethers ( n  5). The method described is fast, precise and accurate, requires little sample preparation and is applicable to a wide variety of compounds.

Prediction of flooding in columns packed with polymer packings

Prediction of flooding in columns packed with polymer packings

Prediction of the lifetime and optimization of polymer and composite bearings and packings

One of the most important factors in the introduction of polymer and composite materials in industry is the development of methods for the reliable prediction of the operational characteristics of a product in the design stage. The existing methods for engineering calculations of friction points (FP), which will imply sliding bearings and packing devices, permit only an estimation of some initial parameters and do not permit prediction of change in these parameters upon use. In addition, the methods for calculating metalbearings and elastomer (rubber) packings do not take account of the specific properties of polymer and composite materials such as the dependence of their physical and mechanical properties on temperature, time, operational parameters, environmental action, and large temperature deformations, which markedly restrict their use for polymer FP. As a result, the introduction of a polymer FP in a dependable design is possible only after carrying out a wide variety of expensive tests, and since the operational lifetime of modern equipment is measured in thousands and even tens of thousands of hours, a long time period and significant cost are required. In the present work, engineering methods are examined for determining criteria for the operational suitability and lifetime, prediction of the operational characteristics of polymer FP taking account of the temperature-forc e-time dependence of the material properties, optimal design, and accelerated testing. Criteria for operational suitability and estimation of the durability of polymer FP relative to permissible wear. The major problem in the design of friction points is determination of permissible operational modes. At present, limiting values of the specific load p, slide velocity v, temperature T, and permissible values of pv and fpv factors (f is the friction coefficient) are common criteria for the operational suitability of FP. As indicated by most workers, the major significance of the pv factor lies in its indication of the temperature in the friction zone,which, in turn, significantly affects the friction characteristics of the FP such as friction loss and wear rate. The experimental determination of these parameters for various materials is carried out, as a rule, on samples or according to the results of tests on simplified models of the FP. In a series of reports [ I, 2], the inadequacy of these methods was indicated. This inadequacy is a consequence of the different requirements for FP, wide variety of experimental methods and experimental equipment, and subjectivity in the interpretation of results. Thus, various parameters differing by more than order of magnitude are given in the specialized literature for the same material [1, 3-6]. A significant disadvantage of the pv (or fpv) criterion is that by characterizing the heat production, it ambiguously determines the temperature in the friction zone. An increase in the sliding velocity v (with constant pv due to a decrease in p) leads to an improvement in the conditions for heat removal due to an increase in the convective component of heat exchange. As shown by our experiments for Ftoroplast-4 teflon packings and F4K20 composite bearings (Fig. 1), a change in the load from 0.3 to 2 MPa and velocity from 0.1to 3 m/sec for the same value of pv leads to a change in temperature by more than a factor of 1.5 (Fig. 2). Since temperature is the major factor determining the rate of wear [7], the pv factor does not permit unequivocal prediction of the wear at an FP. Another disadvantage of present methods for determining permissible values of pv is that they do not take account of the major operational index of a FP, viz., the working time. Thus, estimation of the operational suitability of a planned FP using the available data for (pV)per is difficult, especially in the case of change in the operational mode. Indeed, if the operational mode of a FP presupposes drastic but brief increases in load and velocity as in the forced operation of motors to values considerably exceeding (pV)per, we should not consider that the FP in this case is unequivocally unsuitable since during the action of these values of p and v, catastrophic increase in temperature or.significant increase in wear may not occur. Furthermore, features of FP design which permit, for example, compensation of viscoelastic deformations and improved heat removal from the friction zone and also special lubrication provide for reliable operation of a FP at p, v, and pv significantly exceeding the permissible val~es given in the literature. Hence, the present methods for determining permissible parameters may be used only as a relative evaluation of the friction properties of materials under comparable experimental conditions. The determination of permissible operational

Influence of non-wetted fluored polymer packings in distillation columns—I Hydrodynamics

Packing wettability has a noticeable influence on the hydrodynamics of columns. Non wetted fluored polymer packings are studied in order to determine the pressure drops and flooding conditions compared with wetted glass packing. Experimental results and correlations established will enable a more precise design of industrial columns.

Influence of non-wetted fluored polymer packings in distillation columns—II Mass transfer

This study has been carried out on an industrial extractive distillation unit at atmospheric pressure with the ternary H 2O-HC1-H 2SO 4. The column is packed with non-wetted fluored polymer “Rashig” rings. The mass transfer is noticeably improved when the flooding percentage is high enough compared with classical wetted packings. A correction factor is introduced in Ramm's correlation for the calculation of the height of transfer unit in the liquid phase.

Importance of macropores in polymer packings for gas chromatography

Importance of macropores in polymer packings for gas chromatography

Polymer packings as a means for increasing the corrosion-fatigue resistance of bore pipes

Polymer packings as a means for increasing the corrosion-fatigue resistance of bore pipes