Analytical grade resins

When a fresh bottle of resin is obtained, it should be cleaned very carefully or it will not produce reproducible results. Analytical grade resins have had the treatment described below and can be used immediately. Place the rCsin in a Soxhlet extractor and extract with 2-3 N HCl until the extract is clear. Follow this with 2-3 N NaOH until the extract is clear, and then extract with 95% ethanol until the extract is clear. Rinse with water until the rinsings are neutral and salt free. Keep the resin moist. 

Pre-treatment of the resin. By the column method, wash about 400 g of the analytical grade resin with about 700 ml of 3.0 N hydrochloric acid and then with 4 or 5 litres of water. Transfer the resin to a 1 litre flask, remove most of the water by decantation and shake the resin thoroughly for several minutes with three succesive 100 ml portions of ethanol. Remove the residual ethanol by repeated washing with water and shake the resin vigorously with 400 ml of 0.5 N sodium hydroxide for about 10 minutes. Decant the slightly turbid solution, wash the resin with water until all suspended fine particles have been removed, and filter on a Buchner funnel. Press the resin between filter papers and store it in a glass stoppered bottle sealed with adhesive tape. 

The checkers used analytical grade AG 50W-X8 resin, which is a strongly acidic polystyrene gel type resin, supplied by Bio-Rad Laboratories. The submitters used the large-pore, strongly acidic ion-exchange resin Lewatit SPC 118, supplied by Bayer AG. 

Lypozyme IM-20 (Mucor miehei lipase immobilized on a weak anion-exchange resin) was kindly supplied by Novo Nordisk (Bagsvaerd, Denmark). The gas chromatography (GC) standards (mono-, di-, and trilaurin) were obtained from Sigma (St. Louis, MO). Analytical-grade glycerol, lauric acid (99.9%), n-hexane, ethyl acetate, acetone, and ethanol were purchased from Merck (Darmstadt, Germany). 

Cation exchange resin, strong base, 8% cross linked, 100-200 mesh, analytical grade... 

Add enough analytical grade Dowex 50X8 cation exchange resin, 20-50 mesh, in the hydrogen form, to the solution to make it at least 0.05 M in acid. Filter with suction through a coarse polyethylene or Teflon filter and wash the resin. Neutralize the filtrate with calcium carbonate and concentrate to ca. 400 ml., either in a rotary evaporator or in a Teflon beaker under a heat lamp. 

Chlorotrityl chloride resin was obtained from CBL (Patras). Fmoc-amino acids and their derivatives were purchased either from Advanced Chemtech, Nova-Biochem, SNPE or Bachem (Switzerland). Solvents, AcOH, TFA and TFE were of analytical grade, purchased either from Merck or Fluka and used without further purification. TLC was performed on a precoated silica gel 60 F254 (Merck) aluminium plates employing the following solvent systems chloro-form/methanol/acetic acid (90 12 2) and (85 10 5), toluene/methanol/acetic acid (70 30 15) and (90 10 10). All HPLC runs were performed on a Merck Hitachi... 

Schematic experimental procedure is shown in Figure 1. All the chemicals used were of analytical grade, and ion-exchanged distilled water was used for aU the procedure. Amberhte IRC-76 (Organo K.K.) was used for cation exchange reactions. Its cation exchange capacity for 1 dm of wet resin is 200 g of CaCOs. The resin was treated in the diluted HCl solution to displace Na by H , and then treated in saturated CaCOs solution to displace H+ by Ca . After washing with the distilled water, 1 cm of wet Ca +-resin was dispersed in the 300 cm of the distilled water. Pure CO2 gas was introduced into the resin-dispersed solution at the constant flow rate (10 cm min i). Time variation of the pH value and Cs concentration of the resin-dispersed solution was analyzed by using pH / ion meter (Horiba K.K. model F-23 with pH and calcium ion electrodes).

All gelatin and acacia solutions were deionised by mixing with Amberlite resins IRA-400 + IR-120 for 30 min at 40°C prior to use, unless otherwise stated. This method was adapted from Janus et al (26). The potassium thiocyanate used was of analytical grade from Koch-Light Laboratories Ltd. 

Basic inorganic solids were of analytical grade. Basic organic resins were kindly provided by BAYER (Duolite) and DOW CHEMICALS (Dowex). 

Dowex 50WX8/H resin (400—200 mesh) p.a. (Fluka) Analytical-grade reagents (Sigma-Aldrich or Fisher Scientific)... 

Phenol, formaldehyde in form of a 37% aqueous solution (formalin), and sodium hydroxide were purchased from Sigma Aldrich, Steinheim, Germany. Kraft lignin was supplied in the form of a dried black powder by Mead Westvaco Corporation, Charleston, South Carolina, USA. The salts potassium carbonate, zinc borate, and propylene carbonate were also purchased from Sigma Aldrich, Steinheim, Germany. All chemicals were analytical grade and used as such for the preparation of the resins without further purification. 

Reagents used in the test, including sodium hydroxide, hydrochloric acid, sulfuric acid and cobalt sulfate were analytical grade without farther purification. PC88A extractant was industrial-grade products with a purity of 93%. Acetic acid-sodium acetate buffer solution was prepared on our laboratory. The resin used in the test was the HPD-100 Styrene-divinyl benzene porous adsorbing resins. The cobalt raw materials used in the test are listed in Table 1. 

Resins have spherical particles, and are available in various size ranges. Resins for industrial applications are commonly 14-52 mesh, while those for laboratory use are more usually 50-100, 100-200 or 200-400 mesh. The mesh sizes are only nominal, and analytical grades have a narrower and more symmetrical size distribution than general-purpose resins of the same nominal mesh size. Small particles are more rapidly penetrated by solutes than large ones and therefore come to chemical equilibrium more quickly, but a column packed with small particles offers more resistance to solvent flow than one packed with large particles, and may require excessive pressure to give a useful flow rate. For open-column use, 50-100 mesh resins are satisfactory. Finer resins may be used in pumped columns, and are to be preferred because they require much smaller volumes of eluent 100-200 mesh Dowex 50 with 2% cross-linking requires not much more than half as much 10% methanolic hydrochloric acid for complete elution as the same resin, 50-100 mesh [3]. 

Analytical grade anion-exchange resin (Bio-Rad, AG 1-X4, 1(X)-2(X) mesh or 2CKM00 mesh) was converted from its original chloride form to the perchlorate form by repeated equilibration with concentrated sodium perchlorate solution, first batch-wise in a beaker and finally in a column, until the effluent from the column gave a negative test for chloride. The column was then washed with distilled water to remove excess electrolyte. 

Analytical grade cation-exchange resin (Bio-Rad, AG 50W-X4,100-200 mesh), purchased in the hydrogen form, was converted to the sodium form by neutralizing with sodium hydroxide solution and then washing with acidified sodium perchlorate solution (pH 2) and finally with distilled water. 

Resin Analytical grade mixed bed resin, AG 501-X8, 20 - 50 mesh fully regenerated (Bio-Rad Laboratories, Richmond, Calif.). Prepared by washing with copious quantities of pure methanol for several hours, washing with the 80 - 20 methanol/water solvent and then air-drying. 

The isoelectric pH values of albumin and gelatin were measured by microelectrophoresis and by ion exchange [10]. Hydrochloric acid, sodium hydroxide, sodium chloride and other chemicals used were of analytical grade and obtained from Fisher Scientific, USA. The polyion solutions were prepared by dispersion in distilled water at 40 0.1°C. The polyions were allowed to hydrate completely this took 30 min to 1 h. Following hydration the solutions were deionized by mixing for 30 min at 40 O.UC with Amberlite resins IR-120P and IR-400 before use. This method is an adaptation of that of Janus et al. [57]. 

In summary, barium hydioxide is added to a solution of commercial potassium hydroxide (analytical grade). The precipitate of barium carbonate is allow cd to settle and the excess barium ions removed by passing the solutions through a column of lon-cxchange lesm (.Ambcr-lite IR I 20) which is Liuantitatively in the potassium form RSO.,K (R is the matrix of the resin). The eluate is a olut on of pure potassium hydroxide free from carbonate. 

The sample consisted of a pure aluminum/pure copper couple. A cylinder of pure aluminum (99.999 wt%), provided by Alfa/Aesar, was drilled in its center and a cylinder of pure copper (99.9 wt%), provided by Goodfellow, was then introduced by force into the hole. The assembly of the two materials gave a perfectly joined interface avoiding any crevice corrosion due to surface defects. The diameters of the two cylinders were chosen to obtain an aluminum surface area to copper surface area ratio of 10 (external diameters were equal to 10 and 3.15 mm for the aluminum and copper bars, respectively). The electrode was then embedded in an epoxy resin so that a disk electrode was obtained at the extremity. Before immersion in the electrolyte, the disk electrode was mechanically polished with SiC papers up to 4,000 grade, ultrasonically cleaned with ethanol, then with distilled water. The electrolyte was a 10 MNa2SO4 solution prepared with analytical-grade chemicals in contact with an air atmosphere and at room temperature. 

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