Adsorbents polyurethane

Sucrose acrylate derivatives can be converted into polymers and hydrogels that can be used as flocculants, water adsorbents, bioimplantables, and dmg dehvery devices (42). Sucrose ethers have appHcations as surfactants and surface coatings, and as feedstocks for synthesis of polyurethane foams and... 

Gaseous and particulate pollutants are withdrawn isoldnetically from an emission source and collected in a multicomponent sampling train. Principal components of the train include a high-efficiency glass- or quartz-fiber filter and a packed bed of porous polymeric adsorbent resin (typically XAD-2 or polyurethane foam for PCBs). The filter is used to collect organic-laden particulate materials and the porous polymeric resin to adsorb semivolatile organic species (com-... 

Adsorption of lA of POMs with CV and Malachite Green (MG) on the polyurethane foams (PF) and some other adsorbents is investigated. While lA is fully adsorbed on the PF in wide pH range (0,4 M H SO - pH 4) extent of dye adsoi ption does not exceed 0,4%. lA are adsorbed faster then POMs. Extent of sorption of lA is 60-70% at 5 minutes and is complete after 15 minutes. lA can be eluted from PF most effectively by methylbutylketone, acetone or alcohols can be used too. 

The test-techniques of hydrargyrum (II) and zincum (II) ions determination in aqueous solutions with the use of congo red and brilliant green adsorbed on polyurethane foam accordingly are desighed on the basis of received data for organic reagents adsorption on it s. 

Select mobile phases for HPSEC based on their ability to dissolve the sample and their compatibility with the column. Zorbax PSM columns are compatible with a wide variety of organic and aqueous mobile phases (Table 3.4), but analysts should avoid aqueous mobile phases with a pH greater than 8.5. As mentioned earlier, select mobile phases that minimize adsorption between samples and silica-based packings. Sample elution from the column after the permeation volume indicates that adsorption has occurred. If adsorption is observed or suspected, select a mobile phase that will be more strongly adsorbed onto the silica surface than the sample. For example, N,N-dimethyl-formamide (DMF) is often used for polyurethanes and polyacrylonitrile because it eliminates adsorption and dissolves the polymers. When aqueous mobile phases are required, highly polar macromolecules such as Carbowax can be used to coat the silica surface and eliminate adsorption. Table 3.5 provides a list of recommended mobile-phase conditions for some common polymers. 

The most common methods for trapping pesticide vapors from air use adsorbents. Common air sampling adsorbents include charcoal (derived from petroleum or coconut) and synthetic polymeric materials, such as cross-linked polystyrene and open-cell polyurethane foam. Charcoal has been used for the cumulative sampling of volatile... 

The trapping efficiency of polymeric, microporous adsorbents [e.g., polystyrene, polyurethane foam (PUF), Tenax] for compound vapors will be affected by compound vapor density (i. e., equilibrium vapor pressure). The free energy change required in the transition from the vapor state to the condensed state (e.g., on an adsorbent) is known as the adsorption potential (calories per mole), and this potential is proportional to the ratio of saturation to equilibrium vapor pressure. This means that changes in vapor density (equilibrium vapor pressure) for very volatile compounds, or for compounds that are gases under ambient conditions, can have a dramatic effect on the trapping efficiency for polymeric microporous adsorbents. 

Surface Adsorption Hater sample is passed through a column of the adsorbent and the adsorbed organic constituents subsequently eluted with a smaller volume of organic solvent. All sample types Adsorbents Include charcoal, macroretlcular resins, polyurethane foams, bonded phases and ion-exchangers. Generally have high capacity but sample discrimination may be a -problem. Sample modification and Incomplete recovery are further possible problems. 

Imanishi et al. [33] pointed out that there was an optimum point at which the tethering density of PEO chains makes a polybutadiene urethane surface biocompatible. They also reported that bovine plasma FGN and bovine y-globulin adsorbed on the PEO-modified polyurethane were completely denatured, in comparison with 4-38% denaturation of BSA adsorbed. 

Diazinon has a finite vapor pressure (see Chapter 3) and thus will be present in the air. A method for diazinon in air has been reported that is based on the use of polyurethane foam (PUF) to adsorb the pesticide from the air as the air is pulled through the PUF (Hsu et al. 1988). The PUF is then Soxhlet-extracted and the extract volume reduced prior to capillary GC/MS analysis. An LOD of 55 ng/m3 (5.5 m3 sample) and recovery of 73% were reported. Another study was described in which the diazinon levels in indoor air were monitored following periodic application of the pesticide for insect control (Williams et al. 1987). In this method, air is pulled through a commercially available adsorbent tube to concentrate diazinon. The tube is then extracted with acetone prior to GC/NPD analysis. No data were provided for the LOD, but recoveries in excess of 90% were reported at the 0.1 and 1 pg/m3 levels. This paper also indicated that diazinon can be converted to diazoxon by ozone and NOx in the air during the sampling process. 

To develop the endothelium, provision must be made for attachment of the cells. This attachment can be accomplished by connection to a fibrin capsule, physical attachment to a rough surface (as in a bundle of fibers) or via adsorbed or covalently bonded antigen ligands. We will expand on these concepts (development of endothelium and antithrombic hydrophilic polymers), but it is useful to mention that both strategies are possible with properly formulated polyurethanes. Nonthrombic polyurethanes can conceivably be devised by hydrophilic polyurethanes or by the attachment 2005 by CRC Press LLC... 

Adsorbents. Macroreticular Amberlite resins XAD-2 and XAD-4 (20-50 mesh Lots 90721 and 89829, respectively) were obtained from BDH Chemicals Ltd. Polyurethane foam (upholstery grade, Woodbridge Foam Co.) and vegetable charcoal (Darco G-60 Lot 363-53 Matheson Canada Ltd.) were purchased. 

The resins and the carbon-impregnated polyurethane foam were separately placed in cellulose thimbles and Soxhlet extracted successively for 24 h with HPLC-grade hexane, dichloromethane, acetone, and methanol. The final methanol extract from each adsorbent was concentrated and analyzed by GC by using the FID. 

Two anomalies are distinctly observable in the recovery data. The first feature involves CA, which was not well-retained by the polyurethane-carbon adsorbent either from its individual solution or when mixed with the other five compounds. The effluent from the column contained more CA than was found sorbed onto the adsorbent. Although it is tempting to attribute this lack of sorption to the amino functionality, basicity cannot be the entire reason because DCB with two amino groups behaved normally. Perhaps water solubility could also be a contributing factor. In any event, this result indicates some ineffectiveness of the polyurethane-carbon mixed adsorbent system and shows the need for further investigations of various parameters affecting the recovery of CA or other similar compounds. 

XAD-2 and XAD-4 macroreticular resin adsorbents were found to be adequate to accumulate the organic pollutants considered in the present study except for bis(2-ethylhexyl) phthalate. Polyurethane-carbon ad-... 

Zaranski, M.T., G.W. Patton, L.L. McConnell, T.F. Bidleman, and J.D. Mulik. 1991. Collection of nonpolar organic compounds from ambient air using polyurethane foam - granular adsorbent sandwich cartridges. Anal. Chem. 63 1228-1232. 

Air analysis may be performed by U.S.EPA Method TO 13 (U.S.EPA 1988), which is quite similar to the above method. PAH-bound particles and vapors (many compounds may partially volatilize after collection) may be trapped on a filter and adsorbent (XAD-2, Tenax, or polyurethane foam), and then desorbed with a solvent. The solvent extract is then concentrated and analyzed by HPLC (UV/Fluorescence detection), GC-FID, or GC/MS (preferably in SIM mode). Because of very low level of detection required for many carcinogenic PAHs, including benzo(a)pyrene, the method suggests the sampling of a very high volume of air (more than 300,000 L). 

Preconcentration of Mo from mineral and produced waters has been performed by Ferreira et al. [24], employing polyurethane foam as sorbent, prior to the determination by ET-AAS. The thiocyanate complex of Mo(VI) was adsorbed onto a minicolumn filled with the sorbent, followed by elution with a 3 M HNO3 solution. With an enrichment factor of 10, an LoD of 0.08 p,g l-1 was achieved. Good agreement in the analysis of mineral waters was found between the results of the proposed method and those obtained by ICP-MS. 

Semivolatile analytes in vapor-phase samples are often associated with particulate matter or aerosols that are collected on glass or quartz fiber filters in a flowing air stream.1 However some semivolatile analytes that have higher VPs, for example, 3,3 ,5,5 -tetra-chlorobiphenyl in Fig. 8.2, can slowly vaporize from a particle trapped on a filter in the flowing air stream, and will be lost unless captured by an in-stream sampling device. Small glass or metal tubes containing polyurethane foam are often used to capture vaporized semivolatile analytes. Other-solid phase adsorbents, which are described in the next section, are also used to trap semivolatile analytes vaporized from particulate filters. 

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