Liquid phase polymer retention

Shkinev VM, Gomolitskii VN, Spivakov BY, et al. 1989. Determination of trace heavy metals in waters by atomic-absorption spectrometry after pre-concentration by liquid-phase polymer-based retention. Talanta 36(8) 861-863. 

When ultrafiltration as a separation method is combined with soluble polymers as reagents, the result is a technique that allows to separate solutes, which do bind or not to the polymer, in the homogenous phase. This process was termed Liquid-phase Polymer-based Retention (LPR). ... 

Liquid-phase Polymer-based Retention (LPR) 1985 Nature 315, 313... 

Rivas BL, Pooley SA, Pereira ED, and Maureira A, Water - Soluble polyelectrolytes with metal ion removal ability by using the liquid phase based retention technique, In Proceedings of World Polymer Congress - MACRO 2006, Macromolecular Symposia, Wiley-VCH Verlag GmbH Co, KgaA, Weinheim, 2006 pp. 116—122. 

The technique described above is called liquid-phase polymer-based retention (LPR) or polyelectrolyte-enhanced UF. Another variant of the separation... 

Water soluble cetylpyridinium chloride modified poly(ethyleneimine) 13 were investigated for the removal of several cations (Cu ", Zn , Cd , Pb ", etc.) and anions (POi CrOl") from water [113]. The polymer can form interaction products with negative ions due to electrostatic bonds and also with metal ions due to complex formation. Other basic polymers such as poly(vinylamine), neutral polymers such as polyalcohols and acidic polymers sueh as poly(aerylic acid) were investigated using the method of Liquid-Phase Polymer-Based Retention for the separation of metal ions from aqueous solution [114]. 

Geckeler, K.E., Bayer, E., Spivakov, B.Y., Shkinev, VM. Vorob Eva, G.A. (1986) Liquid-phase polymer-based retention, a new method for separation and preconcentration of elements. Analytica ChimicaActa, 189, 285-292. 

The liquid phases of polar columns are usually the heat-stable polymers of ethyleneglycol and the dibasic acids, succinic or adipic (Table 12.13). Fatty acids are separated on the basis of both chain length and the degree of unsaturation and some columns are capable of resolving fatty acids with the same chain length but different numbers of double bonds (0-6). The saturated fatty acids show the shortest retention times followed by the monoenoic, dienoic, etc. (Figure 12.19). 

The liquid phase and polymer phase activity coefficients were combined from different methods to see if better estimation accuracy could be obtained, since some estimation methods were developed for estimation of activity coefficients in polymers (e.g. GCFLORY, ELBRO-FV) and others have their origins in liquid phase activity coefficient estimation (e.g. UNIFAC). The UNIFAC liquid phase activity coefficient combined with GCFLORY (1990 and 1994 versions) and ELBRO-FV polymer activity coefficients were shown to be the combinations giving the best estimations out of all possible combinations of the different methods. Also included in Table 4-3 are estimations of partition coefficients made using the semi-empirical group contribution method referred to as the Retention Indices Method covered in the next section. 

The generic permselectivity of a membrane can be described by the retention coefficient for liquid phase or the separation factor for gas phase. Separation factor will be defined and discussed in Chapter 7. In the case of liquid-phase membrane separation, the retention coefficient of the membrane can be characterized by some commonly used model molecules such as polyethylene glycol (PEG) polymers which have linear chains and arc more flexible or dextians which arc slightly branched. The choice of these model molecules is due to their relatively low cost. They are quite deviated from the generally... 

The gas-phase tram-alkylation reaction was performed in an automated micro-flow apparatus containing a quartz fixed-bed reactor (i d. 10 mm) at lO Pa [16 vol% benzene (1, p.a., dried on molsieve), 3.2 vol% diethylbenzene (2, consisting of 25% ortho, 73% meta, 2% para isomers, dried on molsieve), N2 balance (50 mL/min), WHSV =1.5 h ] with 2.0 mL of the tube reactor filled with catalyst particles (500-850 pm sieve fraction, typically 1.4 g). Two separate saturators were connected to the inlet of the reactor for the supply of 1 and 2. The partial vapor pressure of 1 and 2 was controlled by adjusting the temperature of the saturator-condensers and the N2 flow rate. After equilibration for 30 min at the applied reaction temperatures (473 K and 673 K, heating rate 10 K/min) within a dry N2 flow (50 mL/min), benzene (1) and diethylbenzene (2) were passed throu the reactor. To prevent condensation of both reactants and products prior to GC analysis [Hewlet Packard 5710 A, column CP-sil 5CB capillary liquid-phase siloxane polymer (100% methyl) 25 m x 0.25 mm, 323 K, carrier gas N2, FID, sample-loop volume 1.01 pL], tubes were heat-traced (398 K). FID sensitivity factors and retention times were determined using ethene (99.5 %, dried over molsieve) and standard solutions of 1, 2, and ethylbenzene (3, 99%) in methanol (p.a.). The conversion of 2 was measured as a function of time [8]. 

These are the styrene-divinyl copolymer type (HIO) and include Porapak, Polypak, and Chromosorb 102. Five different Porapaks are available P, Q, R, S, and T, which differ in degree of cross-linking of styrene with ethylvinyl benzene. These polymers give sharp, symmetrical peaks and low retention volumes for water, alcohols and glycols, while less polar compounds are retarded (B28, Hll). The beads are stable up to about 250°C. As they are generally used without liquid phase, there is no bleed from the column. Figure 2 shows the excellent results obtained... 

In GC, the mobile phase or carrier phase is an inert gas such as helium and the stationary phase is a very thin layer of liquid or polymer on an inert solid support inside a column. The volatile analytes interact with the walls of the column, and are eluted based on the temperature of the column at specific retention times (Grob Barry, 2004). The eluted compoimds are identified with detectors. Flame ionization and mass spectrometry are the most commonly used detectors for flavour analysis (Vas Vekey, 2004). 

Mathiasson, L. Jonsson, J.A. Olsson, A.M. Haraldson, L. Sensitivity of retention index to variations in column liquid loading and sample size. J. Chromatogr. 1978,152, 11-19. CasteUo, G. D Amato, G. Classification of the "polarity of porous polymer bead stationary phases by comparison with squalane and apolane standard liquid phases. J. Chromatogr. 1983, 269,153 160. 

Gas Chromatography. The retention volume of a volatile material on a gas chromatography column is determined by the interaction of the sample with the liquid phase of the column. If the column material is a polymer then a study of the elution behaviour of simple molecules provides information about the physical state of the polymer and about its interactions with the probe molecule. This inverse g.l.c. technique has been much studied and reviewed. The use of inverse g.l.c. to determine crystallinity is based on the insolubility of probe molecules in the crystal phase of a polymer and Braun and Guillet, have discussed sources of error due to non-ideality of solution of the probe molecule. Schneider and Calugaru have used inverse g.l.c. to study phase transitions in polyfethylene terephthalate) and Deshpande and Tyagi report similar studies on polyfvinyl acetate). In recent years there has been some interest in multiphase copolymer systems. Ito et report work on styrene-THF copolymers and Dincer and... 

Gas-liquid Chromatography (g.l.c.).—Letcher has reviewed the use of g.l.c. to obtain activity coefficients in non-poiymer systems. The method is claimed - to be an accurate means of obtaining thermodynamic quantities in binary solutions when the two components differ considerably in volatility. Clearly this applies to many polymer-solvent systems and then the pol3rmer is conveniently made to form the stationary (liquid) phase in standard equipment. The solvent of interest is introduced into the mobile (gas) phase and its specific retention volume measured, from which heats of mixing are calculated > in the limit of zero concentration of solvent (a limit of interest in connection with the removal of volatiles from polymeric materials - ). 

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