Polymer sorbents

Prepai ative isolation of nonvolatile and semivolatile organic compounds fractions (hydrophobic weak acids, hydrophobic weak bases, hydrophobic neutrals, humic and fulvic acids) from natural and drinking waters in optimal conditions was systematically investigated by solid-phase extraction method with porous polymer sorbents followed by isolation from general concentrate of antropogenic and/or toxic semivolatile compounds produced in chlorination and ozonation processes. 

The concept of SPME was first introduced by Belardi and Pawliszyn in 1989. A fiber (usually fused silica) which has been coated on the outside with a suitable polymer sorbent (e.g., polydimethylsiloxane) is dipped into the headspace above the sample or directly into the liquid sample. The pesticides are partitioned from the sample into the sorbent and an equilibrium between the gas or liquid and the sorbent is established. The analytes are thermally desorbed in a GC injector or liquid desorbed in a liquid chromatography (LC) injector. The autosampler has to be specially modified for SPME but otherwise the technique is simple to use, rapid, inexpensive and solvent free. Optimization of the procedure will involve the correct choice of phase, extraction time, ionic strength of the extraction step, temperature and the time and temperature of the desorption step. According to the chemical characteristics of the pesticides determined, the extraction efficiency is often influenced by the sample matrix and pH. 

Note 1 A polymer sorbent may be a polymer adsorbent or a polymer absorbent. The... 

Pap T et al (2002) Effect of solvents on the selectivity of terbutylazine imprinted polymer sorbents used in solid-phase extraction. J Chromatogr A 973(1-2) 1-12... 

Notes The most commonly used porous polymer sorbent is Tenax-GC, although the Porapakand Chromosorb Century series have also been used Tenax-GC has been used with thermal desorption methods, but can release toluene, benzene, and trichloroethylene residues at higher temperatures in addition to Tenax-GC, XAD 2-8, Porapak-N, and Chromosorbs 101, 102, 103, and 106 have found applications, sometimes in stacked sampling devices (for example, a sorbent column of Tenax-GC — Chromosorb 106 in tandem) Chromosorb 106, a very low polarity polymer, has the lowest retention of water with respect to organic materials and is well suited for use as a backup sorbent... 

Tricyclic antidepressants Custom made molecular imprint polymer sorbents Acetonitrile-10 mM sodium acetate, pH 3.0 (98 2) with 0.02% trifluoroacetic acid and 0.015% triethylamine 330 mm x 100 pm i.d. 225 mm packed length... 

Breakthrough Experiments. For the breakthrough experiments the sorbents were packed in 100-mg beds, 4 mm in diameter, and inserted into the six ports in the manifold. The effluent ends of the tubes were connected to a common line leading to the flame ionization detector. While the flame ionization detector, calibrated with the challenge atmosphere, monitored the concentration of vinyl acetate in the combined bed effluents, the pump in the detector drew the challenge atmosphere through each bed at approximately 0.2 L/min. The output from the detector, the breakthrough curve, was recorded with a strip-chart recorder. Most of the porous polymer sorbents tested were first washed with acetone and dried. 

Table I. Systems of Polymer-Sorbent-Eluent Where Limiting Conditions Have Been Observed...

Vallano PT, Remcho VT (2000) Highly selective separations by capillary electrochromatography molecular imprint polymer sorbents. J Chromatogr A 887(2) 125-135... 

Fly. 10.8. Universal sorbents Chemical structures of Waters Oasis a) HLB and (fe) MXC polymer sorbents. The top structure in b) is the basic drug propanolol demonstrating drug-sorbent interaction. [From D. A. Wells, LC.GC, 17(7) (1999) 600. Reproduced by permission of LC.GC.]... 

The above principles of the method are indicative of its great potential and flexibility (see, e.g., Beroza [141] and Tumlinson and Heath [142]). Rcker and Sievers [146,147] proposed to apply selective complexation by a europium(lll) coordination polymer sorbent for the pre-fractionation of volatile compounds (e.g., ketones, aldehydes, alcohols and carboxylic acids). 

K.l. Sakodynsky and L.I. Panina, Polymernye Sorbenty dlya Molekulyarnoy Khromatografii (Polymer Sorbents for Molecular Chromatography), Nauka, Moscow, 1977. 

Very few studies have reported on the stability of herbicides, including triazines and degradation products, on SPE materials.In addition to time and space savings, the stabihzation of pesticides on these materials makes it possible to use SPE techniques for onsite extraction. Sabik et al. demonstrated the stabihty of 20 urea and triazine herbicides, including four degradation products, on GCB material over a two month period. LiSka and Bilikova studied the stabihty of 16 polar pesticides including triazines, carbamates, and phenylureas sorbed on to a polymer sorbent. They found that most of these remained stable over a seven-week period. Crescenzi... 

III) coordination polymer sorbent to trap selectively various oxygenated compounds from a complex mixture of urinary volatile metabolites. 

Light hydrocarbons C1-C4. Light hydrocarbons are frequently determined in the atmosphere, since some of them contribute to photochemical smog formation. In most cases, data are required about the concentration of particular components and thus, the analysis is performed on gas chromatographs, equipped with a flame ionization detector. The light hydrocarbons should be concentrated, usually by a polymer sorbent [32], prior to the analysis. 

A special case of porous polymer sorbent is polyurethane foam, which can be used to collect large air samples up to 100 m (Ligocki and Pankow, 1985). A major application of PU foams is the trapping of high boiling organopesticides such as lindane or per-methrine. 

Other adsorbents show a specific background as well Tirkkonen et al. (1995) present a compilation of compounds that were found under thermal desorption conditions for seven carbon-based and porous-polymer sorbents. 

The changes in system constants with composition of a binary mixture of carbon dioxide and 1,1,1,2-tetrafluoroethane on a column containing a porous polymer sorbent are illustrated by the results in Figure 7.7 [20]. Adding 1,1,1,2-tetrafluoroethane to... 

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