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At least 325 records · Page 18Linked to original sources
PubMed2000

Optimization of ion-exchange displacement separations. II. Comparison of displacement separations on various ion-exchange resins.

A variety of stationary-phase materials are currently available for the chromatographic purification of biomolecules. However, the effect of various resin characteristics on the performance of displacement chromatography has not been studied in depth. In Part I, a novel iterative scheme was presented for the rapid optimization of displacement separations in ion-exchange systems. In this article, the optimization scheme is employed to identify the optimum operating conditions for displacement separations on various ion-exchange resin materials. In addition, the effect of different classes of separation problems (e.g., diverging, converging or parallel affinity lines) on the performance of displacement separations is also presented. The solid film linear driving force model is employed in concert with the Steric Mass Action isotherm to describe the chromatographic behavior in these systems. The results presented in this article provide insight into the effects of resin capacity and efficiency as well as the type of separation problem on the performance of various ion-exchange displacement systems.

Algorithms↗
PubMed1999

Determination of clenbuterol in bovine urine using gas chromatography-mass spectrometry following clean-up on an ion-exchange resin.

A gas chromatographic-mass spectrometric method was developed for the determination of residues of clenbuterol in bovine urine. The method involves a simple cation-exchange clean-up and concentration of clenbuterol in the acidified urine, followed by ethyl acetate extraction. The analyte is determined as the di-trimethylsilyl derivative and quantitated against an internal standard of penbutolol. Using a 5-ml sample of urine, a detection limit of 0.07 ng/ml can be achieved with recoveries close to 100% for fortification levels of 0.2 and 1 ng/ml. By increasing the sample volume to 50 ml, a detection limit below 0.01 ng/ml was achievable with recovery averaging 70%. The coefficient of variation of the assay ranged from 15% at 0.01 ng/ml (50-ml sample) to 6% at 1 ng/ml (5-ml sample). It was demonstrated that the method can detect the presence of clenbuterol in bovine urine at sub-ppb (ng/ml) levels using low resolution GC-MS with electron impact (EI) ionization.

Animals↗
PubMed1976

[Automation of urine hydroxyproline assay after isolation hydrolysis of hypropeptides on ion exchange resin].

Urinary hydroxyproline is mainly in the form of oligopeptide and polypeptide, with a low proportion of free amino acid. Overall or partial estimation of hydroxyprolinuria may be carried out after isolation and hydrolysis of the peptides on ion exchange resin, by an automatic, continuous flow technique. This method presents a certain number of advantages, such as, selectivity, sensitivity and practicability, compared with that which we proposed in 1968. Determination of the criteria of quality of the method shows that it is suitable for exploration of variations in hydroxyprolinuria in diseases of bone and collagen. The reference values in relation to age and sex are also reported.

Adolescent↗
PubMed1994

Ion exchange resins for ophthalmic delivery.

A new novel delivery system for ophthalmic drugs was developed using an antiglaucoma agent Betaxolol Hydrochloride as a model. The new delivery system involved both the binding and release of drug from ion exchange resin particles. Betaxolol was studied in-vitro via a release model analysis. The ocular comfort of Betaxolol was greatly enhanced by reducing the availability of free drug molecules in the precorneal tear film. The amount of resin concentration was selected to obtain optimum binding of the drug. The zeta potential of suspended particles was adjusted to produce flocculated suspension. Drug resin particles were then incorporated into the structured vehicle, containing Carbomer 934P as a polymer, to enhance the physical stability and ease of resuspendability of the product. This delivery system also optimized the bioavailability of Betaxolol, reducing the total drug concentration in half to 0.25% Betaxolol in 0.25% BETOPTIC S Ophthalmic Suspension as compared with 0.5% Betaxolol in BETOPTIC 0.5% Sterile Ophthalmic Solution dosage form. Increased comfort of 0.25% BETOPTIC S Ophthalmic Suspension, as well as its bioequivalency data in animal models (rabbits), was confirmed in actual clinical trials of the product 0.25% BETOPTIC S Ophthalmic Suspension. The 0.25% BETOPTIC S Ophthalmic Suspension product has been approved gamma FDA and is marketed in U. S. since February 1990. The 0.25% BETOPTIC S Ophthalmic Suspension formulation has an increased bioavailability (equivalent to BETOPTIC 0.5% Sterile Ophthalmic Solution at half the concentration of drug); and pharmaceutically, is an elegant suspension product which settles slowly providing uniform dosage and increased ocular comfort.

Acrylic Resins↗