Resins cleaning procedures

Resin Cleaning Procedure. Prior to use in a sampler, the resins must be cleaned to remove preservatives and the monomeric chemical residues that are byproducts of their production. The cleaning procedure recommended by Rohm and Haas is the following (29) ... 

Recommended Solvent Selection Procedure. Resin contaminants have been identified only recently. Until 1977, only the following resin contaminants were identified naphthalene, ethylbenzene, and benzoic acid (36). The resin cleaning procedure of Junk et al. (5), which uses a series of three solvents of decreasing polarity, removes the widest possible variety of organic contaminants from the resins. This method is necessary when many compounds must be removed. 

Cleaning the Wires and Fittings. Different types of resin with different characteristics require varying degrees of cleanliness. The following cleaning procedure was used for one type of polyester resin with which over 800 tensile tests were made on ropes in sizes -J- in. (6.5 mm) to 3- -in. (90 mm) diameter without experiencing any failure in the resin socket attachment. 

Resin evaluation of both new and used resins (titration of total binding sites, total protein capacity, flow vs. pressure, particle size distribution, total organic carbon removed by cleaning procedures, and microbial and endotoxin analysis)... 

Various additional (secondary solvent cleaning) procedures have been proposed, including vacuum distillation [30], treatment with macroreticular anion-exchange resins [31], and treatment with activated alumina [32,33]. These secondary cleanup operations increase solvent quality, and continue to be studied to better evaluate their process and economic advantages. In the French UP3 Purex plant, vacuum distillation is used to regulate TBP concentration and solvent quality with beneficial effects. The latter include... 

Junk et al. (5) found that the Rohm and Haas procedure (29) did not clean the resin sufficiently for use as an adsorbent for recovering nanogram-per-liter amounts of organic materials. Junk s resin preparation and cleaning procedure started with backwashing the resin with water to remove fines, sodium chloride, and sodium carbonate. 

This study used the Junk et al. (5) procedure for resin cleaning beginning with a water backwash. The remaining steps consisted of sequential Soxhlet extraction of 24-h duration for each of the following solvents methanol, acetonitrile, and ethyl ether. This process was followed by a final rinse of 2 bed volumes of 1 N sodium hydroxide. Ethyl ether was replaced by whatever sample eluting solvent was to be used. Approximately 700 mL of wet resin was Soxhlet extracted with 900 mL of solvent. The solvent distillation rate was approximately 30 mL/min. After extraction, each of the unconcentrated solvents was analyzed by capillary GC with a flame ionization detector (FID) and GC-mass spectrometry (GC-MS). 

A comparative study was conducted by cleaning XAD-2 resin by ultrasonic and Soxhlet extraction procedures. Two batches of XAD-2 resins from the same lot of uncleaned resin were cleaned by backwashing with water and then were subsequently extracted with methanol, acetonitrile, and methylene chloride. The solvent-to-resin volume ratio for both methods was 5 1. The volumes of wet resin for the Soxhlet extraction and the ultrasonic bath were 100 mL and 50 mL, respectively. The ultrasonic cleaning procedure was done in a Teflon-lined screw-cap amber jar (250 mL) for 1 h in each solvent. The Soxhlet extraction sequence was 24 h in methanol, 24 h in acetonitrile, and 48 h in methylene chloride. 

The cleaning procedure does not remove the materials from the micropores in the resin, and they are slowly removed with each nonpolar elution (Rohm and Haas) (34). 

Currently, much more is known about resin contaminants. The major contaminants of XAD-2 and XAD-8 resins have been identified by GC-MS (Tables II and III). It may now be possible to optimize the cleaning procedure by selecting solvents that effectively remove the known contaminants. Time and cost needed to prepare resins for sampler use could thus be reduced. 

Exley et al. [61] found aluminum in practically all reagents used in a study of the inhibition of hexokinase activity by this element. The way to overcome the problem was cleaning the solutions using an aminophosphonate chelation resin. The procedure reduced the contamination of ATP and NADP to approximately 5% and 10% of their initial values, respectively, but the resin was ineffective in removing aluminum from magnesium acetate or the enzyme glucose 6-phosphate dehydrogenase. Probably the conditions were not favorable for the resin to pick up the aluminum ions from these solutions. It is important to remember that, if there is an affinity between aluminum and the species in solution, a competition between this species and the resin will take place. 

By careful apphcation of heat or solvent to a thermoplastic substrate, one may liquefy the surface resin and nse it to form the bond. With thermal or solvent welding, surface preparation is not as critical as with adhesive bonding. The bond strength is determined by diffusion of polymer from one surface into another instead of by the wetting and adsorption of an adhesive layer. However, with welding some form of pretreatment may still be necessary. Certainly, the parts should be clean, and all mold release and contaminants mnst be removed by standard cleaning procedures. 

The polished sample is removed from the encapsulating resin, cleaned according to the previously described procedures, and properly fixed onto the SIMS sample holder. Although different SIMS-compatible epoxy resins are available, the introduction of the resin encapsulated bronze sample into the SIMS analysis chamber is preferentially avoided due to the prolonged outgas-sing in the vacuum chamber required. 

Anion-exchange resin Make a slurry of Biorad AG 1-X8 resin (100-200 mesh) in distilled water. Pipette into the exchange colunm. When using cheaper Dowex resin make up small amounts to prevent size fractionation. The slurry may be stored in closed bottle, but unacidified slurry may grow bacteria. It is common practice to discard the resin after use, but some laboratories develop cleaning procedures to recycle it. 

Some quantitative data concerning the cleaning procedure and resin purity are presented in this symposium by McCann et al. (21). 

In order to suppress interferences due to the presence of inorganic species and reliably determine the proteinaceous composition of the sample, a clean-up step has often been introduced in the analytical procedure. This step may include the extraction of the proteinaceous matter by an ammonia solution [8], the use of a cation-exchange resin [8,55], a chelating agent [9,41,44], the use of a Cig resin or the use of barium chloride solution to suppress sulfates [10,81,82]. Table 9.1 reports the methods used to overcome such problems. 

Picer and Picer [357] evaluated the application ofXAD-2, XAD-4, and Tenax macroreticular resins for concentrations of chlorinated insecticides and polychlorinated biphenyls in seawater prior to analysis by electron capture gas chromatography. The solvents that were used eluted not only the chlorinated hydrocarbons of interest but also other electron capture sensitive materials, so that eluates had to be purified. The eluates from the Tenax column were combined and the non-polar phase was separated from the polar phase in a glass separating funnel. Then the polar phase was extracted twice with n-pentane. The -pentane extract was dried over anhydrous sodium sulfate, concentrated to 1 ml and cleaned on an alumina column using a modification of the method described by Holden and Marsden. The eluates were placed on a silica gel column for the separation of PCBs from DDT, its metabolites, and dieldrin using a procedure described by Snyder and Reinert [359] and Picer and Abel [360]. 

Cotterill [222] has developed a procedure, discussed below, in which the herbicides are extracted from soil with saturated calcium hydroxide solution. After clean-up the residues are ethylated using iodoethane and tetrabutylammonium hydrogen sulphate as counter ion. Liquid-liquid partition and the use of a macroreticular resin column were compared as clean-up steps and the reaction conditions for optimum yield of ethyl ester were evaluated. 

The urine of people who are heavy smokers contains mutagenic chemicals, chemicals that cause mutations in biological cells. Bioanalytical laboratories can analyze urine samples for these chemicals, but the samples must be cleaned up first prior to extraction with methylene chloride. The procedure for this cleanup utilizes an open column chromatography. Columns several inches tall and about an inch wide are prepared by packing them with an adsorbing resin that has been treated with methyl alcohol. The urine samples are passed through these columns as part of the sample preparation scheme. 

Solution-phase synthesis [5] often needs purification or clean-up procedures after each reaction step to remove excess reagent. These methods include scavenging, extractions and associated plate transfers. All these procedures cause the loss of the desired compound. Although the purity can be improved after treatment, the chemical yield is seriously compromised. In contrast, SPOS has a unique advantage in purifying bound compound without losing compound mass. However, if the reaction is not complete at each step, the side products will form on resin and they cannot be removed while bound to the resin. The final yield and purity wiU both suffer as a result. A 90% yield for a four-step synthesis wiU produce the final product in a disappointing 65% yield. 

Maple Block Screening Method. A series of experimental procedures were performed on bonding maple block wood (Cook, P. M., Eastman Kodak at Kingsport, TN, personal communications, 1987). The procedure adopted was the ASTM D 905 standard, modified as follows Sugar maple (Acer saccharum) wood, 76 by 25 by 5.7 mm in size (3 inches long, 1 inch wide, and 0.25 inch thick), with 6% moisture content was planed to obtain fresh surfaces for bonding. The desired amount of resin (with no mix additives) was weighed (58.6 g/m2, 12 lb/1000 ft2, resin solids basis) and applied to one block surface and then a second clean block was overlapped so that 25 square mm (1 square inch) surface area common to each block was coated. The resin coated blocks were placed directly in the hot press (no clamp time). The blocks were hot pressed at 177°C (350°F) for 4 to 6 minutes at 3.44 MPa (500 psi). All bonded blocks were allowed to... 

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