Resin sorbents

Mean recoveries are for triplicate determinations from drinking water, spiked at 0.5-5 ppb (nominally 1 ppb), using XAD-4 resin sorbent columns. 

Egorov, O., Grate, J. W., and Ruzicka, J., Automation of radiochemical analysis by flow injection techniques Am-Pu separation using TRU-resin sorbent extraction column, J. Radioanal. Nucl. Chem., 234, 231-235, 1998. 

To confirm the above observations, an additional set of experiments were performed using a different sorbate probe, n-heptane. Once again, as with benzene, the retention volume was found to decrease in a similar manner with increasing gas pressure on the crosslinked resin sorbent. As shown in both... 

FIGURE 2. Structural components of macroporous resin sorbents suitable for concentrating aquatic humic substances. 

Table I summarizes the adsorption selection incorporated into the experimental studies. Four pre-purified synthetic resin sorbents obtained from Alltech Associates (Deerfield, IL) were used along with an activated carbon sample (Union Carbide Grade 6GC) procured from our pilot plant. The coarse particle size of the selected adsorbents in conjunction with the column dimensions and experimental flow rates yielded very small pressure drops (< 2 atm) across the sorbent bed, as ascertained by inlet and outlet pressure gauges before and after the column, respectively. Because of this small pressure gradient within the sorbent column, the recorded experimental breakthrough data were taken essentially at isobaric conditions.

The results of this work indicated that sequential determination of the heats of ion exchange on sorbent or adsorbent surfaces give a unique insight into the performance of individual resin sorbents, which offers a good potential for a prediction of the performance of the resins in practical applications. 

Artificial Internal Organs and Related Fields.— There has been a marked increase in certain aspects of the literature here, notably in the haemoperfusion field and in total artificial heart replacement. Some recent advances in haemodialysis techniques have been described involving high rates of ultra-filtration combined with optimal diffusion, the use of a resin-sorbent system for dialysate regeneration and the use of urease (E.C. 3.5.1.5) and an expanded polytetrafluoroethylene membrane in the development of a new method of urea removal. The effects of different membranes in the onset of haemodialysis-induced leucopenia have been discussed. ... 

Ion exchange is a process in which cations or anions in a Hquid are exchanged with cations or anions on a soHd sorbent. Cations are interchanged with other cations, anions are exchanged with other anions, and electroneutraUty is maintained in both the Hquid and soHd phases. The process is reversible, which allows extended use of the sorbent resin before replacement is necessary. 

Last time development of methods of iodine determination, which include preliminary sorption preconcentration of microcomponents and their subsequent determination in phase of concentrate get great practical significance. Silica gel (SG) with adsorptively modified quaternary ammonium salts (QAS) gets properties of anion-exchange resin. The sorbents modified in this way can be used successfully for determination of different anions. 

S. B. Hawthorne, D. J. Miller and M. S. Kiieger, Coupled SPE-GC a rapid and simple technique for excacting, identifying and quantitating organic analytes from solids and sorbent resins , 7. Chromatogr. Sci. 21 347-354 (1989). 

N. Masque, M. Galia, R. M. Marce and E. Boirull, Chemically modified polymeric resin used as sorbent in a solid-phase exti action process to determine phenolic compounds in water , J. Chromatogr. 771 55 - 61 (1997). 

Recently, new approaches of sorbent construction for reversed-phase chromatography have been developed. Silicas modified with hydrocarbon chains have been investigated the most and broadly utilized for these aims. Silica-based materials possess sufficient stability only in the pH 2-8 range. Polymeric HPLC sorbents remove these limitations. Tweeten et al. [108] demonstrated the application of stroongly crosslinked styrene-divinylbenzene resins for reversed-phase chromatography of peptides. 

In studies of mice, rats, and dogs, diisopropyl methylphosphonate was rapidly absorbed into plasma (Hart 1976). The plasma data indicate that all three species rapidly absorbed diisopropyl methylphosphonate, although the exact rate was species specific. Although no studies were located regarding human absorption, diisopropyl methylphosphonate is also likely to be absorbed rapidly into the plasma of humans. The ability of porous polymeric sorbents, activated carbon, and dialysis to remove diisopropyl methylphosphonate from human plasma has been studied (McPhillips 1983). The grafted butyl-XAD-4 was found to be the most efficient sorbent for the removal of diisopropyl methylphosphonate from human plasma. Hemoperfusion of plasma over synthetic XAD-4 or butyl-XAD-4 sorbent resin was more efficient than dialysis/ultrafiltration for the removal of diisopropyl methylphosphonate from human plasma the smaller surface of the packed resins provided less area to minimize damage to molecular constituents of the plasma. These methods are useful in reducing diisopropyl methylphosphonate concentrations in the plasma. However, since diisopropyl methylphosphonate and its metabolites are not retained by the body, the need for methods to reduce body burden is uncertain. 

As the concentration of Na+, K+, Ca2+, Mg2+, Cl" ions in potable water can have the value of 100 - 500 mg/1 and the concentration of radionuclides is very low, the sorbents must have high selectivity and distribution coefficient of Cs+, Sr2+, Co2+, I" ions. Unfortunately most of known resins cannot be used for these purposes. 

The reaction is reversible and therefore the products should be removed from the reaction zone to improve conversion. The process was catalyzed by a commercially available poly(styrene-divinyl benzene) support, which played the dual role of catalyst and selective sorbent. The affinity of this resin was the highest for water, followed by ethanol, acetic acid, and finally ethyl acetate. The mathematical analysis was based on an equilibrium dispersive model where mass transfer resistances were neglected. Although many experiments were performed at different fed compositions, we will focus here on the one exhibiting the most complex behavior see Fig. 5. 

The esterification of acetic acid with ethanol using sulfonic ion-exchange resins as catalyst/selective sorbent was studied by Mazzotti et al. [164]. The authors developed a detailed mathematical model, which was able to predict correctly the system s behavior. They succeeded in obtaining 100% conversion of acetic acid in addition to a complete separation. Several other studies involving enzymatic reactions were also carried out and will be presented in more detail in the next section. 

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