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PubMedDate not supplied

Solid phase extraction purification of carboxylic acid products from 96-well format solution phase synthesis with DOWEX 1x8-400 formate anion exchange resin.

The anion exchange resin DOWEX 1x8-400 formate has been developed for the isolation or resin capture of carboxylic acids from solution phase reactions in a 96-well format using a batchwise solid phase extraction technique. Eleven different anion exchange resins (formate forms) were evaluated for their efficiency at scavenging aryl and aliphatic carboxylic acids from solution. The model carboxylic acids had pK(a)s ranging from 3.40 to 4.89. Exchange efficiency onto the resin was pK(a) dependent with the carboxylic acids but not with their diisopropylethylammonium salts. Exchange off of the resin also showed pK(a) dependence with the stronger acids requiring more concentrated solvent acid for exchange. DOWEX 1x8-400 formate was determined to have superior capacity and the fastest exchange rate. Solvents suitable for exchanging the acids onto the resin were CH2Cl2, methanol, and various solvent/water mixtures. Solvents suitable for exchanging the carboxylic acids off of the resin were TFA/solvent or HCO2H/solvent mixtures. The resin was found to swell best in CH2Cl2 and in polar protic solvents such as water, alcohols, and acids. Application of this technique to the crude product mixtures from an arrayed reductive amination and an arrayed Stille reaction provided product carboxylic acids in yields averaging 57% and purities averaging 89%.

Journal Article↗
PubMed1975

Treatment of pruritus in cholestasis of pregnancy with a new anion exchange resin (Secholex).

Anion exchange resins form a non-absorbable complex with bile acids in the intestine, thus removing bile acids from the enterohepatic circulation and facilitating bile acid excretion in the faeces. A new bile acid sequestrant (PDX chloride, Secholex) was evaluated for the relief of pruritus in cholestasis of pregnancy (CP) in 31 women. CP was verified by the presence of the abnormal lipoprotein X in serum and the clinical series was divided into two degrees of severity, pruritus gravidarum (PG) and hepatosis of pregnancy (HP) based on liver function tests. Eleven of 31 women discontinued treatment because of gastro-intestinal side effects. Of the 20 women continuing the study for more than one week, all with a milder form of cholestasis, PG (n=8), experienced relief of pruritus, while some relief was obtained in 75% of the women with HP. After up to 4 weeks administration of Secholex, no obvious interference with fat absorption was evident judging from the serum lecithin content of linoleic and arachidonic acids. A reduction in serum folic acid might indicate an interaction in folic acid absorption. An expected reduction in serum cholesterol levels which are characteristically increased in CP, was not achieved by the administration of Secholex.

Anion Exchange Resins↗
PubMed1989

Experimental study on the adsorption of excess heparin with anion exchange resin fiber.

Anion exchange resin fiber (Ionex) was used as a heparin adsorbent. Ionex has the adsorption capacity of 70 mg/g (weight by desiccation) for heparin, and was used in an attempt to remove the heparin from blood-perfused artificial organs, before the blood was transfused back into the patients. In the ex vivo study, the 5 systemically heparinized dogs (500 U/kg) were treated with a 35-40 g column of Ionex, by direct hemoperfusion (DHP). The concentration of heparin was significantly reduced, within 15 to 60 minutes, using the Ionex. This suggested the possibility of removing excess heparin from the living body. In in vitro, the relationship between the amount of heparin by Ionex and the blood-flow volume were evaluated. Whole blood taken from dogs was added to 5 U/ml of heparin. This was then introduced into a small column containing 0.9 g Ionex, at blood-flow rates of 0.8, 1.6, and 3.2 ml/min. A good adsorption capacity was shown at the blood-flow rate of 0.8 ml/min. One possible explanation for this is that the heparin dispersed in the blood cells gradually was passed on into the plasma and, so, did not have time to be adsorbed at the faster flow rates.

Adsorption↗
PubMed2000

Comparison of chromatographic ion-exchange resins. I. Strong anion-exchange resins.

A comparative study has been undertaken on various strong anion-exchangers to investigate the pH dependence, titration curves, efficiency, binding strength, and dynamic capacity of the chromatographic resins. The resins tested included: Macro-Prep 25Q, TSK-Gel Q-5PW-HR, Poros QE/M, Q Sepharose FF, Q HyperD 20, Q Zirconia, Source 30Q, Fractogel EMD TMAE 650s, and Express-Ion Q. Testing was performed with five different proteins: Anti-FVII Mab (IgG), aprotinin, BSA, lipolase, and myoglobin. The dependence of pH on retention varies from generally low to very high for proteins with low pI. No direct link between pH dependence on retention and titration curves of the different resins was observed. Efficiency results show the expected trend of lower dependence of the plate height with increasing flow-rate of resins for medium and high pressure operation compared to the soft resins. Binding to the anion-exchange resins as a function of ionic strength may vary depending on the specific protein. Generally, binding and elution at a high salt concentration may be performed with Poros QE/M or Macro-Prep 25Q, while binding and elution at low salt concentration may be done with TSK-Gel Q-5PW. Dynamic capacities are strongly dependent on the specific protein employed and for some resins dependent on the flow-rate. A general good agreement was obtained between this study and data obtained by suppliers for the dynamic capacity. The results of this study may be used for selection of resins for testing in process development, however, the data does not tell anything about specific selectivity differences or resolution between a target protein and a given impurity. None of the resins studied here should be regarded as good or bad, but more or less suitable for a specific purpose, and only testing for the specific application will determine which one is the optimal resin.

Anion Exchange Resins↗
PubMed2005

Compatibility between self-etching adhesive and self-curing resin by addition of anion exchange resin.

OBJECTIVE: The aim was to investigate whether anion exchange resin powder in the OH(-) form, added to the amine component of self-cured resin can deprotonize acid groups of a self-etching adhesive and thus eliminate incompatibility caused by amine neutralization. METHODS: Shear bond strength (SBS) of a self-cured CorePaste (COP), bonded either with all-in-one adhesive iBond (IBO) or with IBO coated with a self-cured experimental resin (SCR), loaded with 0, 8, 16, or 32 wt% of anion exchange resin powder (AER) in OH- form, were determined on 80 enamel and dentin surfaces each after 24 h water storage. IBO specimens were either light-activated or not. Flexural modulus and strength of the four SCR resins were determined by three-point bending. Data was analyzed by one-way ANOVA and Duncan's post hoc test (p<0.05). RESULTS: Enamel SBSs of COP on IBO were 20-25 MPa, in combination with SCR (0 up to 32%) >25 MPa for activated or non-activated IBO. COP on IBO produced no bond on dentin, with the non-loaded SCR 5-10 MPa SBS was achieved, and 15 and 21 MPa were measured with the three AER-loaded SCRs on activated and non-activated IBO, respectively. Flexural moduli of SCR with 0 and 8% AER were higher than with 16 and 32%. Flexural strengths were not significantly different. SIGNIFICANCE: Addition of anion exchange resin to the amine component of self-cured resin is an effective means of enhancing the bond strength on dentin and to prevent amine neutralization through the acid groups of self-etching primer adhesives.

Acid Etching, Dental↗
PubMed1985

Further characterization of bacterial adherence to urinary bladder mucosa: comparison with adherence to anion exchange resin.

Bacterial adherence to anion exchange resin has recently been reported to provide a useful, rapid, in vitro screening assay for identifying putative antiadherence agents. The studies presented in this report provide additional evidence that adherence to anion exchange resin is similar to urinary bladder mucosa adherence. Results are as follows. 1) Heparin inhibits the adherence of Escherichia coli, Klebsiella ozaenae, Proteus mirabilis, Streptococcus fecalis and Pseudomonas aeruginosa to both the mucin deficient bladder and anion exchange resin. 2) Drugs which inhibit E. coli adherence to the bladder also inhibit E. coli adherence to the resin and conversely, drugs which do not effect E. coli adherence to the resin do not affect attachment to the bladder. 3) Extracts from mammalian urinary bladder mucosa prevent E. coli adherence to both the bladder and resin. 4) The ability of heparin to displace preattached bacteria from anion exchange resin is inversely proportional to the time the bacteria are in contact with resin. Similar results were obtained for the ability of heparin to displace bacteria from the bladder. These studies indicate that bacterial adherence to anion exchange resin responds to heparin and other chemical agents in a manner similar to the mucin deficient rabbit urinary bladder. Because of the ease and rapid nature of this in vitro assay, it serves as a useful screen for potential bacterial antiadherence agents and could be used to help elucidate mechanisms of bacterial attachment.

Adhesiveness↗
PubMed1980

Separation of gangliosides on a new type of anion-exchange resin.

A new anion exchange resin, Spherosil-DEAE-Dextran, consisting of porous glass beads covered with cross-linked DEAE-Dextran, was used in the separation of gangliosides. The gangliosides were eluted from the resin with a discontinuous gradient of potassium acetate in methanol, separating the gangliosides quantitatively into mono-, di, tri-, tetra- and pentasialoganglioside fractions. The new resin was found to have higher binding capacity, to show less unspecific adsorption and to give a better separation of the higher oligosialogangliosides than did DEA-Spherosil, QAE-Sephadex, DEAE-Sephadex and DEAE-Sepharose. Anion exchange chromatography improved discrimination between closely allied gangliosides as well as quantification and identification of individual gangliosides, especially the minor ones. The new procedure was used in the separation of the gangliosides in human infant forebrain and cerebellum.

Adult↗
PubMed2001

Comparison of chromatographic ion-exchange resins. II. More strong anion-exchange resins.

A comparative study was performed on strong anion exchangers to investigate the pH dependence, titration curves, efficiency, binding strength, particle size distribution, and static and dynamic capacity of the chromatographic resins. The resins tested included Q Sepharose XL, UNO Q-1, Poros 50 HQ, Toyopearl QAE 550c, Separon HemaBio 1000Q, Q-Cellthru Bigbeads Plus, Q Sepharose HP and Toyopearl SuperQ 650s. Testing was performed with five different proteins: anti-Factor VII monoclonal antibody (immunoglobulin G), aprotinin, bovine serum albumin, lipolase and myoglobin. The dependence of pH on retention varies from generally low to very high for proteins with a low isoelectric point (pl). An unexpected binding at pH 7-8 of aprotinin with pI >11 was observed on Separon HemaBio 1000Q. No link between pH dependence on retention and titration curves of the different resins was observed. Efficiency results show the expected trend of higher dependence of the plate height with increasing flow-rate of soft resins compared to resins for medium- and high-pressure operation. No or a very small difference in particle size distribution was obtained between new and used resins. Binding to anion-exchange resins as a function of ionic strength varies to some extent depending on the specific protein. Generally, binding and elution at high salt concentration may be performed with Q Sepharose XL, Toyopearl QAE 550c, Q Sepharose HP and Poros 50 HQ, while binding and elution at low salt concentration may be performed with Q-Cellthru Bigbeads Plus. A very high binding capacity was obtained with Q Sepharose XL. Comparison of static capacity and dynamic capacity at 10% breakthrough shows approx. 50-80% utilization of the total available capacity during chromatographic operation. A general good agreement was obtained between this study and data obtained by the suppliers. The results of this study may be used for selection of resins for testing in process development.

Anion Exchange Resins↗
PubMed1998

Decline in plasma retinol in unconjugated hyperbilirubinemia treated with bilirubin adsorption using an anion-exchange resin.

When an anion-exchange resin column (Plasorba BR-350) was used for the treatment of unconjugated hyperbilirubinemia, we found an unexpected decrease in plasma retinol (vitamin A) concentrations in a patient with type I Crigler-Najjar syndrome. The purpose of our study was to investigate the mechanism of this decrease in plasma retinol. When the patient's serum bilirubin exceeded the bilirubin binding capacity of 14.7 mumol bilirubin/g serum albumin (i.e., 720 mumol/L of bilirubin), abrupt deterioration of the patient's neurologic status (suppression in his gait and speech) occurred, so the need to apply plasmapheresis to reduce the unconjugated bilirubin was indicated. Blood was drawn from the radial artery at a flow rate of 160 mL/min and pumped into a membrane plasma separator at a rate of 40 mL/min. The plasma was passed through the bilirubin adsorbent column and returned to the venous blood line of the plasma separator. Plasma samples were taken at the inlet and outlet of the bilirubin adsorbent column before and after treatment. The concentration of unconjugated bilirubin in plasma was effectively reduced by the perfusion, but plasma retinol was coincidentally decreased by the perfusion to vitamin A deficiency levels. The patient's plasma retinol was 2,127 nmol/L at the beginning of therapy and decreased to 1,492 nmol/L after repeated adsorption treatments. As the amounts of decrease in retinol (912 +/- 123 nmol/L) after the perfusion were almost equal to those in retinol-binding protein (1,010 +/- 192 nmol/L), retinol may have been removed as a form of holo retinol-binding protein. Decreases in retinol and retinol-binding protein levels were also observed in low-density lipoprotein (LDL) apheresis with a dextran sulfate column (i.e., a cation-exchange resin column). In the patient with Crigler-Najjar syndrome, retinol taken dietarily was removed by plasmapheresis. However, the patient manifested no clinical symptoms associated with vitamin A deficiency, since his liver storage of retinol could supply the loss caused by plasmapheresis treatment. We should measure plasma retinol concentrations to evaluate the loss of retinol during plasmapheresis treatment coupled with an anion-exchange resin column.

Adolescent↗
PubMed2002

Simultaneous uptake of anionic surfactants and micellar-solubilized contaminants using anion-exchange resins.

This research studied simultaneous uptake of anionic surfactants and micellar-solubilized organic contaminants by anion-exchange resins. Anionic surfactant molecules adsorbed onto the positively charged resin mainly through electrostatic attraction, while the micellar-solubilized contaminants were excluded from aqueous solutions once the remaining micelles could no longer solubilize them. Data suggest that the excess contaminants adsorbed onto the resin skeleton and admicelle layer formed on the resin surface through hydrophobic interactions and eventually partitioned into the resin gel phase matrix. In batch adsorption, the contaminant solubilization capacity did not decrease linearly with respect to surfactant concentration decrease due to the increased solution counterion activity during anion exchange, and caused "delayed" contaminant uptake relative to that of the surfactant. No such effect occurred in continuous column adsorption, where the surfactant and contaminant breakthrough occurred simultaneously. Surfactant head and tail group properties, along with resin structure and particle size significantly affected surfactant and contaminant uptake rates. Relative to recovering the surfactant, the high exchange potential of the anionic surfactant prevented effective surfactant desorption, even at high electrolyte concentration and in the presence of a cosolvent. The resin matrix also had high affinity for the partitioned contaminant, and the contaminant elution from the resin seemed to be controlled by equilibrium partitioning.

Adsorption↗
PubMed2004

Ion-exchange selectivity of anion exchange resin modified with polystyrenesulfonic acid.

In order to change the ion-exchange selectivity of anion-exchange resin, the surface of a gel-type anion exchange resin was modified with anionic polyelectrolyte, polystyrenesulfonic acid. Using this modified resin, the ion-exchange rate of nitrate was little decreased, but that of sulfate was evidently decreased. It is considered that the ion-exchange reaction of the multivalent anion is suppressed by the greater electrostatic repulsive force against the modification layer than that against the monovalent anion. Thus, this modified resin may be suitable for the selective separation of monovalent anions. The influence of the modified condition on the ion-exchange rate was examined. Furthermore, this modified resin was used to separate nitrate ions from sulfate ions in the aqueous solution.

Anion Exchange Resins↗
PubMed2005

Solid-state storage of Ag nanoparticles in anion exchange resin beads and their recovery.

This paper reports the idea and describes a method of reversible storage and recovery of silver nanoparticles (NPs) in anion exchange resin beads based on the principle of ion exchange. We also report that similar exchange of NPs was not possible with cation exchange resins. The Ag NPs were stored by simple exchange of anions of the resins, which were activated with OH- and NO3- ions. FTIR spectroscopic measurements support that the Ag NPs were exchanged with NO3- ions in the resins. The so-stored NPs could be regenerated by addition of NaBH4 solution to the resins. These NPs were recovered and subsequently utilized for catalytic reduction of an organic dye (eosin). Powder X-ray diffraction (XRD) pattern indicated storage of the NPs in the form of various oxides of silver in the resin, with the peak value of intensity corresponding to XRD of the NPs not changing with time. Scanning electron microscopic measurements show that the NPs in the beads were stable for over a month without the formation of any apparent agglomeration.

Journal Article↗