Ion exchangers Amberlite

Sodium 2-mercaptoethanesulfonate (MESNA) [19767-45-4] M 164.2, pKj <0 (SOj ), pK 9.53 (SH). It can be recrystd from H2O and does not melt below 250°. It can be purified further by converting to the free acid by passing a 2M soln through an ion exchange (Amberlite IR-120) column in the acid form, evaporating the eluate in a vacuum to give the acid as a viscous oil (readily dec) which can be checked by acid and SH titration. It is then dissolved in H2O, carefully neutralised with aqueous NaOH, evaporated and recrystd from H2O [7 Am Chem Soc 77 6231 1955]. 

The fact that the material in question has passed over an acidic ion exchanger, CMC-cellulose, a basic one, TEAE-cellu-lose, a Sephadex column and yet another acidic ion exchanger, Amberlite XE-64, resulting in a 10, 000-fole increase in hormonal activity, without any detectable change in the ratio cholecystokinin pancreozymin, speaks in favor of the assumption that both activities are exerted by one and the same substance. 

Recovery and Purification. The dalbaheptides are present in both the fermentation broth and the mycelial mass, from which they can be extracted with acetone or methanol, or by raising the pH of the harvested material, eg, to a pH of 10.5—11 for A47934 (16) (44) and A41030 (41) and actaplanin (Table 2) (28). A detailed review on the isolation of dalbaheptides has been written (14). Recovery from aqueous solution is made by ion pair (avoparcin) or butanol (teicoplanin) extraction. The described isolation schemes use ion-exchange matrices such as Dowex and Amberlite IR, acidic alumina, cross-linked polymeric adsorbents such as Diaion HP and Amberlite XAD, cation-exchange dextran gel (Sephadex), and polyamides in various sequences. Reverse-phase hplc, ion-exchange, or affinity resins may be used for further purification (14,89). 

Tetramethylammonium hydroxide (5H2O) [10424-65-4 (5H2O), 75-59-2 (aq soln) ] M 181.2, m 63°, 65-68°. Freed from chloride ions by passage through an ion-exchange column (Amberlite IRA-400, prepared in its OH" form by passing 2M NaOH until the effluent was free from chloride ions, then washed with distilled H2O until neutral). A modification, to obtain carbonate-free hydroxide, uses the method of Davies and Nancollas [Nature 165 237 1950]. 

Phospholipids. For the removal of ionic contaminants from raw zwitterionic phospholipids, most lipids were purified twice by mixed-bed ionic exchange (Amberlite AB-2) of methanolic solutions. (About Ig of lipid in lOmL of MeOH). With both runs the first ImL of the eluate was discarded. The main fraction of the solution was evaporated at 40°C under dry N2 and recryst three times from n-pentane. The resulting white powder was dried for about 4h at 50° under reduced pressure and stored at 3°. Some samples were purified by mixed-bed ion exchange of aqueous suspensions of the crystal/liquid crystal phase. [Kaatze et al. J Phys Chem 89 2565 7955.]... 

Filtered broth was passed at 2.5 ml/min through a resin column (2.5 cm diameter, 28 cm length) packed with 150 ml of ion exchange resin Amberlite IRC-50 sodium type (Rohm and Haas Co., U.S.A.). The column was washed with water, eluted with 0.5 N HCI at a flow rate 1.3 ml/min. The eluates were fractionated each 10 ml and tuberactinomycin-N activity was found at fractions No. 45-63 obsarved by ultraviolet absorption method and bioassay. 

To a solution of 5 g of sisomicin in 250 ml of water add 1 N sulfuric acid until the pH of the solution is adjusted to about 5. To the solution of sisomicin sulfuric acid addition salt thereby formed, add 2 ml of acetaldehyde, stir for 10 minutes, then add 0.B5 g of sodium cyanoborohydride. Continue stirring at room temperature for 15 minutes, then concentrate solution In vacuo to a volume of about 100 ml, treat the solution with a basic ion exchange resin [e.g., Amberlite IRA401S (OH )], then lyophilize to a residue comprising 1-N-ethyl-sisomicin. 

Exhausted liquid ion exchangers may be regenerated in an analogous manner to ion exchange resins, e.g. Amberlite LA.l saturated with nitrate ions can be converted to the chloride form by treatment with excess sodium chloride solution. 

Silica gel supported sodium metaperiodate was used for the selective oxidation of dibenzyl sulphide80. Metaperiodate anion soaked on strongly basic-ion-exchange resins Amberlite IRA-904 or Amberlyst A-26 was found to be able to oxidize sulphides into the corresponding sulphoxides in 82-99% yield81. 

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