Styrene divinylbenzene copolymer analysis

This type of analysis requires several chromatographic columns and detectors. Hydrocarbons are measured with the aid of a flame ionization detector FID, while the other gases are analyzed using a katharometer. A large number of combinations of columns is possible considering the commutations between columns and, potentially, backflushing of the carrier gas. As an example, the hydrocarbons can be separated by a column packed with silicone or alumina while O2, N2 and CO will require a molecular sieve column. H2S is a special case because this gas is fixed irreversibly on a number of chromatographic supports. Its separation can be achieved on certain kinds of supports such as Porapak which are styrene-divinylbenzene copolymers. This type of phase is also used to analyze CO2 and water. 

The Shodex GPC KF-600 series is packed with 3- im styrene-divinylbenzene copolymer gels in a column having a volume of about one-third compared to standard-types of columns, which are best suited for reducing the organie solvents eonsumption, shortening the analysis time, and lowering the detection limit (Table 6.5). 

These small columns,(usually 10 mm X 1-4.6 mm i.d.) are normally packed with 10-40 p.m sorbents such as Cig-bonded silica, Cg-bonded silica or styrene-divinylbenzene copolymer. These sorbents are not very selective and more selective sorbents, such as the immunosorbent (94), have also been used with good results. Coupling of SPE-gas chromatography is in fact the one most often used in environmental analysis because it reaches a high level of trace enrichment, eliminates water and elutes retained compounds easily with an organic solvent that can be injected into the gas chromatograph. 

Alcohol sulfates and alcohol ether sulfates separated by HPLC on a styrene-divinylbenzene copolymer column with 4 1 (v/v) methanol and 0.05 M ammonium acetate aqueous solution as the mobile phase were analyzed by simultaneous inductively coupled argon plasma vacuum emission spectroscopy (IPC), monitoring the 180.7-nm sulfur line as a sulfur-specific detector [294]. This method was applied to the analysis of these surfactants in untreated wastewaters. 

There are a large number of literature references that refer the use of SPE cartridges for the extraction of pesticides from water. There are several comprehensive reviews of the use of SPE, including that by Soriano et al. who discussed the advantages and limitations of a number of sorbents for the analysis of carbamates. Hennion reviewed the properties and uses of carbon based materials for extraction of a wide multiclass range of pesticides. Thorstensen et al. described the use of a high-capacity cross-linked polystyrene-based polymer for the SPE of phenoxy acids and bentazone, and Tanabe et al reported the use of a styrene-divinylbenzene copolymer for the determination of 90 pesticides and related compounds in river water. SPE cartridges are also widely used for the cleanup of solvent extracts, as described below. 

Anchoring polymers are prepared from chloromethylated styrene-divinylbenzene copolymers of either 1 equiv Cl/g or 4 equiv Cl/g capacity. These resins arc stirred for 24 h in refluxing CHC13, with either 1,4-diazabicyclo[2.2.2]octane, hexamethylenetetramine, or TMEDA. The polymers are filtered off, washed with ClIClj, acetone and Et20, then dried overnight under vacuum at 25 °C. Nitrogen elemental analysis and chloride ion titration gives a value of 80-90% quaternarization. 

Reversed-phase LC is ideally suited for the analysis of polar and ionogenic analytes, and as such is ideally suited to be applied in LC-MS. Reversed-phase LC is the most widely used LC method. Probably, over 50% of the analytical applications are preformed by reversed-phase LC. Nonpolar, chemically-modified silica or other nonpolar packing materials, such as styrene-divinylbenzene copolymers (XAD, PRP) or hybrid silicon-carbon particles (XTerra), are used as stationary phases in combination with aqueous-organic solvent mixtures. Silica-based packing materials are used more frequently than polymeric packing materials. 

In order to improve the separation efficiency and speed in biopolymer analysis a variety of new packing materials have been developed. These developments aim at reducing the effect of slow diffusion between mobile and stationary phase, which is important in the analysis of macromolecules due to their slow diffusion properties. Perfusion phases [13] are produced from highly cross-linked styrene-divinylbenzene copolymers with two types of pores through-pores with a diameter of 600-800 mu and diffusion pores of 80-150 nm. Both the internal and the external surface is covered with the chemically bonded stationary phase. The improved efficiency and separation speed result from the fact that the biopolymers do not have to enter the particles by diffusion only, but are transported into the through-pores by mobile-phase flow. 

The selection of packing materials for SPE (Ch. 1.5.3) is especially important in multi-residue analysis. In general, nonspecific trapping on hydrophobic surfaces like Cig-bonded silica or styrene-divinylbenzene copolymers, e.g., PLRP-S, is preferred. 

Tatsuzawa et aq 36,37,45,59 separat.ed cold drugs and neuroleptics by using a styrene-divinyl benzene-methyl methacrylate copolymer as stationary phase. The best results were obtained with methanol - ammonia (99 1) as mobile phase. The effect of the pH and of the composition of the mobile phase on the separation were discussed. Aramaki et al.70 analyzed a series of alkaloids on a macroporous styrene-divinylbenzene copolymer with alkaline acetonitrile - water mixtures as mobile phase (Fig. 7.10). The columns showed excellent stability, and also under the strong basic conditions used for the analysis of the alkaloids. 

Styrene/divinylbenzene copolymers are the most widely used substrate materials. Since they are stable in the pH range between 0 and 14, eluents with extreme pH values may be used. This allows the conversion of compounds such as carbohydrates, which are not ionic at neutral pH, into the anionic form, making them available for ion chromatographic analysis (see also Section 3.3.5.3). 

Parameters such as solvent, basic medium and reaction time, affecting the derivatization of alcohols and phenols with benzoyl chloride, were investigated. End analysis was by GC with UVD . a sensitive method proposed for trace determination of phenols in water consists of preconcentration by SPE with a commercial styrene-divinylbenzene copolymer, acylation with pentafluorobenzoyl chloride in the presence of tetrabutylammonium bromide and end analysis by GC with either ECD or ITD-MS. LOD was 3 to 20 ngL for ECD and 10 to 60 ngL for ITD-MS, with 500 mL samples . Acylation with the fluorinated glutaric acid derivative 43 was proposed for determination of urinary phenols, as indicative of exposure to benzene and other aromatic hydrocarbons. End analysis by GC-MS shows strong molecular ions of the derivatives by electron ionization. The proto-nated ions are the base peaks obtained by chemical ionization. LOD was 0.5 mgL and the linearity range 0-100 mg L for phenol . 

For a good discussion of on-line SPE coupled to HPLC, the work of Hennion and Pichon (1994) and Hennion and co-workers (1990) discuss environmental applications. In their work, the styrene-divinylbenzene copolymers are used as SPE columns with good capacity for many of the environmentally relevant contaminants and allow for direct analysis by HPLC. Hennion and Pichon (1994) discuss and review a number of studies on pesticides and related compounds by on-line SPE. There is also more discussion of on-line SPE methods coupled to GC/MS in Chapter 10. 

A specific application of environmental SPE is sample preparation of extra-large volumes (from 10 to 100 L). This work was pioneered in the early 1970s by Junk and co-workers (1974) for the analysis of trace organic compounds in water using styrene-divinylbenzene copolymers (XAD-2 resin from Rohm and Haas) and by Thurman and Malcolm (1981) and Leenheer and Stuber (1981) for the analysis of natural organic substances in water (humic substances). One can obtain the XAD resins from Supelco (Appendix Products Guide) and still follow the protocol of this early work for the isolation of contaminants and humic substances from large volumes of water (10-1000 L of water). 

The biogenic components that interfere with the GC analysis of aromatic hydrocarbons are primarily long-chain components. Such compounds are much larger molecules than the compact aromatic hydrocarbons. Because of this major difference, gel permeation chromatography (GPC), which separates on the basis of molecular size, can be used very effectively to separate the two classes of compounds (9). The GPC materials that can be used for the separation include modified dextrans, for example, Sephadex LH-20, and styrene-divinylbenzene copolymers, for example, BioBeads, Styragel, or /x-Styragel. 

An elegant example of the use of GC/MS in the analysis of pesticides in river water is given by Vreuls et al. A 1-ml sample was collected in an LC sample loop and the internal standard added. The sample was then displaced through a short column 1 cm long with a 2 mm I.D. packed with 10 mm particles of a proprietary PLRP-S adsorbent (styrene-divinylbenzene copolymer) by a stream of pure... 

P NMR spectroscopy was used as a nondestructive method to determine TBP activity on TVEX-TBP materials by comparison with activity of TBP in pure samples. The signal width of TBP in TVEX matrix is only 1.5 to 2 times broader as compared with signal width for liquid tri-butylphosphate, indicating the drop-liquid state of extractant (TBP) in matrix pores. TBP signal width increases at extractant partial washout by acetone due to the increase of portion of extractant adsorbed by TVEX matrix the total washout leads to the extractant signal disappearance. However, according to chemical analysis, TVEX matrix still contains 2 to 5% TBP after complete extractant washout. This fact indicates that tri-butylphosphate is dissolved partially in TVEX matrix and acts as plasticizer of styrene-divinylbenzene copolymer. 

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