Rupert Brown

Unilever (United Kingdom)

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Ian T. Norton

University of Birmingham

Vladimir I. Lozinsky

A. N. Nesmeyanov Institute of Organoelement Compounds

Lilija G. Damshkaln

A. N. Nesmeyanov Institute of Organoelement Compounds

S. J. Hauser

Centenary College of Louisiana

Linda A. Rihbany

T Anitha Susan

United States Food and Drug Administration

P. J. Perry

Touro University California

Kristiana Gordon

St George's, University of London

Philip J. Schneider

The Ohio State University

Ross D Kirchhoefer

United States Food and Drug Administration

Cooperative Institutions

United States Food and Drug Administration

American Association of Colleges of Pharmacy

A. N. Nesmeyanov Institute of Organoelement Compounds

Russian Academy of Sciences

Centenary College of Louisiana

Touro University California

University of Iowa

University of Iowa Hospitals and Clinics

St George's, University of London

City St George's, University of London

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Study of cryostructuration of polymer systems. XVI. Freeze-thaw-induced effects in the low concentration systems amylopectin-water

Journal of Applied Polymer Science (2000)

Vladimir I. Lozinsky Lilija G. Damshkaln Rupert Brown Ian T. Norton

Studies of the freeze–thaw behavior of low-concentrated (0.01–0.25 g/dL) water solutions and dilute pastes (0.5–1.0 g/dL) of maize starch amylopectin showed that cryogenic treatment of these systems resulted in the formation of precipitated matter, whose yield and thermal characteristics (melting temperature and enthalpy) depended on the initial polymer concentration and conditions of freezing, frozen storage, and thawing. Research of the kinetic features of these cryoprecipitation events revealed at least two stages for this process: (i) a rapid stage, when the precipitation of virtually all of the dissolved polysaccharide occurred while the system was freezing, and (ii) a slower stage, the rate of which was mainly dependent on the thawing regimes or duration of the sample storage frozen at subzero temperatures. Cryoprecipitation phenomena were observed to be most extensive at temperatures 1–2° below the melting point of the frozen system. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1740–1748, 2000

10.1002/(sici)1097-4628(20000401)75:14<1740::aid-app8>3.0.co;2-1

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Citations (31)

Study of cryostructuration of polymer systems. XXI. Cryotropic gel formation of the water–maltodextrin systems

Journal of Applied Polymer Science (2001)

Vladimir I. Lozinsky Lilija G. Damshkaln Rupert Brown Ian T. Norton

Abstract The freeze–thaw behavior of water solutions containing dissolved maltodextrin (MD; enzymatically converted potato starch derivative with MW of 8000 Da) over a wide range of MD concentration (0.1–15 g/dL) and freezing temperatures from −24 to −6°C was studied. Cryogenic treatment of these systems resulted in the formation of precipitates or gels, whose yield and thermal characteristics (fusion temperature and enthalpy) depended on the initial polymer concentration and conditions of freezing, frozen storage, and thawing. There appeared to be at least two stages to this process: (i) a rapid stage, when partial insolubilization occurred while the system was freezing, and (ii) a slower stage, the rate of which was dependent mainly on the thawing regimes used or the duration of storage at subzero temperatures. In this respect, the cryostructuration of MD was very similar to the freeze–thaw behavior of amylopectin/amylose and locust bean gum water solutions studied earlier. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1658–1667, 2002

Maltodextrin

Locust bean gum

10.1002/app.10077

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Citations (21)

Study of cryostructuring of polymer systems. XIX. On the nature of intermolecular links in the cryogels of locust bean gum

Polymer International (2000)

Vladimir I. Lozinsky Lilija G. Damshkaln Rupert Brown Ian T. Norton

In this study of freeze–thaw-induced gelation of aqueous locust bean gum (LBG) solutions we found that gel formation proceeded through at least two kinetic stages. Initially, rather weak spongy cryostructurates were formed as a result of freezing the system, but their strength and thermostability (fusion temperature) could be increased considerably by means of thawing out the system sufficiently slowly. Preparation of LBG cryogels in the presence of chaotropic (urea) and anti-chaotropic (sodium sulfate) substances showed that the major mechanism responsible for stabilization of junction zones in these gel materials was hydrogen bonding. Therefore, use of the agents facilitating formation of hydrogen bonds enabled the gelation of LBG solutions without the need for synergistic polymers or cryogenic treatments. © 2000 Society of Chemical Industry

Chaotropic agent

Locust bean gum

Thermostability

10.1002/1097-0126(200011)49:11<1434::aid-pi525>3.0.co;2-f

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Citations (45)

Semiautomated Method for the Analysis of Chlorpheniramine Maleate Tablets: Collaborative Study

Journal of AOAC INTERNATIONAL (1979)

Ross D Kirchhoefer Rupert Brown J P Gleason S. J. Hauser Rita E Kling

Abstract A semiautomated method for the analysis of chlorpheniramine maleate tablets, which is based on the USP XIX general assay for salts of organic nitrogenous bases, was collaboratively studied by 6 laboratories. Collaborators were supplied with 4 composites from 4 manufacturers. In the method, the active ingredient is dissolved in dilute HC1, sampled, made basic with dilute NaOH, and extracted with isooctane. The isooctane phase is resampled and the drug is re-extracted into dilute HCL. The absorbance of the acidic aqueous solution is measured at 265 nm. The Associate Referee assayed the collaborative samples to compare the semiautomated and USP XIX methods, and found close agreement in the results from the 2 methods. In the collaborative study of the semiautomated method, there was excellent agreement of the results obtained by the collaborators. The coefficients of variation ranged from 0.46 to 2.24%. The method has been adopted as official first action.

Chlorpheniramine Maleate

Absorbance

Ingredient

10.1093/jaoac/62.6.1197

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Citations (1)

Study of cryostructuration of polymer systems. XVIII. Freeze-thaw influence on water-solubilized artificial mixtures of amylopectin and amylose

Journal of Applied Polymer Science (2000)

Vladimir I. Lozinsky Lilija G. Damshkaln Rupert Brown Ian T. Norton

The effects caused by cryogenic treatment (freezing–frozen storage–thawing) of 0.5–2.0 g/dL solutions of individual starch polysaccharides, namely, amylopectin (solvents: water or 0.35M NaCl aqueous solution) and amylose (solvent: 0.35M NaCl aqueous solution), and also of 0.5 g/dL solutions of their artificial mixtures with various amylopectin/amylose ratios were studied. Freezing of these systems at temperatures from −6 to −24°C for 18 h and subsequent thawing resulted in the formation of cryogelled or cryoprecipitated matter whose morphology and yield depended on the type of polysaccharide, initial polymer concentration, portion of each macromolecular component in the mixed systems, and conditions of cryogenic treatment. Comparison of the process efficiency in the mixed systems during the formation of precipitates (from storage at room temperature) and cryoprecipitates (as a result of cryogenic treatment) revealed the promoting effects of the freezing–thawing influence on polymer–polymer association and showed the presence of some synergism in the mutual interaction of these polysaccharides. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 371–381, 2000

10.1002/1097-4628(20001010)78:2<371::aid-app170>3.0.co;2-b

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Citations (32)

Liquid Chromatographic Determination of Methyldopa and Methyldopa-Thiazide Combinations in Tablets: Collaborative Study

Journal of AOAC INTERNATIONAL (1984)

T Anitha Susan Rupert Brown L A Dougherty John B. Schepman Y H Doucette

A reverse phase liquid chromatographic method for the determination of methyldopa, methyldopa-hydrochlorothiazide, and methyldopachlorothiazide in tablets was collaboratively studied by 8 laboratories. Each collaborator received 20 samples that included drug substance, synthetic and commercial tablet compositions. The overall repeatability and reproducibility standard deviations for commercial tablets were 1.11 and 1.75% for methyldopa, 0.96 and 1.62% for chlorothiazide, and 1.21 and 2.15% for hydrochlorothiazide, respectively. The overall recoveries of methyldopa, chlorothiazide, and hydrochlorothiazide added to synthetic tablets were 100.78, 100.70, and 101.34%, respectively. The method has been adopted official first action.

Methyldopa

Chlorothiazide

Thiazide

Repeatability

10.1093/jaoac/67.6.1118

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Citations (3)