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Biomedical subjects

P H Elworthy

Publications and source records attributed to P H Elworthy.

At least 19 recordsLinked to original sources
PubMed1990

Effect of structural variations of non-ionic surfactants on surface properties: surfactants with semi-polar hydrophobes.

The surface properties of a series of non-ionic surfactants in which a polar group (either an ether or a keto group) has been introduced into a hydrocarbon chain of octadecylpolyoxyethylene glycol monoether (C18E17-19) have been investigated. Surface tension measurements indicated that the critical micelle concentrations for these semi-polar surfactants in aqueous solution were all significantly higher than those of C18E22, the corresponding unsubstituted octadecylpolyoxyethylene glycol monoether. The minimum areas per molecule of the semi-polar surfactants in the surface monolayer were all larger than the area obtained for C18E22, from which it was concluded that the hydrophobe, and not the polyoxyethylene chain was the main determinant of surface area.

Micelles↗
PubMed1989

Effect of structural variations of non-ionic surfactants on micellar properties and solubilization: surfactants with semi-polar hydrophobes.

Novel non-ionic surfactants have been synthesized in which a polar group (either an ether or a keto group) has been introduced into the hydrocarbon chain of an octadecylpolyoxyethylene glycol monoether (C18En) with an oxyethylene chain length, n, of 17-18 units. Light scattering studies have indicated aggregation numbers for these semi-polar surfactants in aqueous solution of between 55-65% of that of an unsubstituted octadecylpolyoxyethylene glycol monoether, C18E22. The solubilizing capacities of the semi-polar surfactant micelles for test compounds which were mainly solubilized at the polyoxyethylene/core interface were lower than those of C18E22 whilst solubilizates which exhibited a reasonable degree of solubility in both the interface and the micellar core showed an increased solubilization.

Chemical Phenomena↗
PubMed1984

Evidence for the intrusion of polyoxyethylene into the hydrocarbon core of non-ionic surfactant micelles.

The intrinsic viscosities, [eta], of non-ionic surfactants of structure, CH3[CH2]m-1[OCH2OCH2]1.25mOH, were measured in water at 298 K. [eta] increased linearly with hydrocarbon chain length from m = 3 to m = 15, and between m = 17 and m = 31. There was a discontinuity between m = 15 and m = 17, which was attributed to intrusion of some polyoxyethylene into part of the hydrocarbon core for surfactants in which m greater than 15. This effect gave a micellar hydration which was lower than expected for the higher members of the series. Other factors relevant to the intrusion of polyoxyethylene into hydrocarbon are discussed.

Colloids↗
PubMed1984

A nuclear magnetic resonance (nmr) investigation of the micellar structure of a long-chain non-ionic surfactant.

Peak integrals, peak widths at half-height (delta nu 1/2), spin-lattice relaxation times (T1), and chemical shifts (delta) of the alkyl and oxyethylene protons of CH3(CH2)21[OCH2CH2]27OH (C22E27) were measured in D2O at various temperatures. The peak integrals, delta nu 1/2, and delta values of the alkyl protons showed a large dependence on temperature below 313K, while the values for the oxyethylene protons were unaffected by temperature. These observations were explained by considering an intrusion of some oxyethylene groups into the hydrocarbon core of the micelle.

Chemical Phenomena↗
PubMed1982

Extended Hildebrand solubility approach and the log linear solubility equation.

The log linear solubility equation, log S = log Sw + sigma f, was studied in relationship to the extended Hildebrand solubility approach. It is shown that the log linear form may be derived beginning with the extended Hildebrand approach. The log linear expression gives a good linear fit for semipolar drugs in a number of water-cosolvent mixtures. It is particularly successful when the solubility parameter, delta 1, of the cosolvent is 3 or more solubility parameter units larger than the solubility parameter, delta 2, of the drug. When the cosolvent tends to solvate the drug strongly, the log linear function may even hold where the solubility parameters of the drug and cosolvent are similar. It appears, however, not to be applicable to nonpolar cosolvent systems. An interfacial model for the solubility of drugs in polar mixed solvents is based on sigma, a parameter that also figures prominently in the log linear solubility equation. When used to describe mixed solvent systems, the interfacial model applies in the region of the solubility profile (solubility versus solvent composition) where the log linear relationships hold. The extended Hildebrand solubility approach is applicable over a wide range of cosolvent composition in mixed systems from nonpolar organic solvents to water.

Aminobenzoates↗
PubMed1982

Effects of structural variations of non-ionic surfactants on micellar properties and solubilization: variation of oxyethylene content on properties of C22 monoethers.

Studies on erucyl alcohol ethoxylated with 40 and 47 units, and on behenyl alcohol ethoxylated with 33 and 43 units, gave values of 106, 101, 271, and 304 (all X 10(3)) for the micellar weight, 51,42,152, and 137 for the aggregation numbers, and 257,362,209, and 311 moles water mol-1 surfactant for the micellar hydration, respectively. Measurements of the solubilization of azobenzene, cortisone acetate, griseofulvin, sulphadiazine, phenylbutazone, betamethasone, tolbutamide, and menaphthone showed that the erucyl derivatives were better solubilizers than the behenyl compounds, and that solubilization increased as the polyoxyethylene chain was shortened; this change was more pronounced with the erucyl compounds.

Chemical Phenomena↗
PubMed1982

Demonstration of maximum solubilization in a polyoxyethylene alkyl ether series of non-ionic surfactants.

The solubilization of azobenzene, menaphthone, cortisone acetate, and griseofulvin was measured in a series of non-ionic surfactants of structure CH3[CH2](m-1) [OCH2CH2]1.25m OH, where m varied from 8 to 18. Maximum solubilization occurs when m = 16 (the hexadecyl alkyl ether). This is explained in terms of changes in the oxyethylene mantle close to the micelle core/mantle interface, which appears to be the main locus of solubilization. Micellar properties of CH3[CH2]17[OCH2CH2]22OH are also reported and discussed.

Micelles↗
PubMed1981

Effects of structural variations on non-ionic surfactants on micellar properties and solubilization: surfactants containing very long hydrocarbon chains.

Polyoxyethylene mono-ethers of dotriacontanol (C32E41) and 4,9-dimethyltritriacontanol (C35E40) have been synthesized. The micellar weights in water at 298K were 4.82 x 10(5) and 5.90 x 10(5), the aggregation numbers 212 and 260, and the levels of hydration 290 and 283 mol water mol-1 surfactant, respectively. The solubilization of azobenzene, cortisone acetate, griseofulvin, sulphadiazine, phenylbutazone, betamethasone, tolbutamide, and menaphthone was studied in 2% solutions of the above surfactants. The presence of large micelles did not result in increased solubilization; C32E41 and C35E40 had a lower solubilizing capacity than that of cetomacrogol.

Colloids↗
PubMed1980

Effects of structural variations of non-ionic surfactants on micellar properties and solubilization: surfactants based on erucyl and behenyl (C22) alcohols.

Studies on erucyl alcohol ethoxylated with 24 units and on behenyl alcohol ethoxylated with 21 ethylene oxide units gave values of 10.2 x 10(3) and 25.4 x 10(3) for the micellar weights, 74 and 203 for the aggregation number, and 134 and 106 moles water mole-1 surfactant for the micellar hydration, respectively. The solubilization of azobenzene, cortisone acetate, griseofulvin, sulphadiazine, phenylbutazone, betamethasone, tolbutamide, and menaphthone was studied in 2% solutions of the above surfactants, and in cetomacrogol. Excluding sulphadiazine, a linear relationship was found between moles solubilized/mole surfactant, and (log P)/molar volume of solubilizate.

Colloids↗
PubMed1976

Oxytetracyline tablet formulations: effect of variations in binder concentration and volume on granule and tablet properties.

Formulation studies have been conducted on an oxytetracycline dihydrate tablet formulation containing microcrystalline cellulose and alginic acid, wet granulated with polyvinylpyrrolidone (PVP) solution. A range of granule properties including size, strength packing and porosity, and tablet properties including breaking load, porosity, disintegration and dissolution have been measured. Increased compaction pressure decreased tablet porosity. The reproducibility of the above properties was determined by tests on nine standard batches of granules and tablets. An increased concentration of PVP in the binder solution decreased the rate of tablet dissolution. Although the volume of granulating solution apparently controlled the granule size, it did not significantly alter the tablet dissolution, when the amount of PVP was constant.

Excipients↗
PubMed1976

Oxytetracycline tablet formulations: the influence of excipients and the method of granulation.

The proportion of microcrystalline cellulose and alginic acid present as excipients in the dry mix for an oxytetracycline dihydrate tablet formulation, prepared by a conventional wet granulation process, has been shown to influence granule formation and properties. Granule size distributions have varied widely due perhaps to variation in binder distribution. Granulating with water was equally satisfactory to granulating with a PVP solution. Slugged granules produced robust tablets, which disintegrated and dissolved rapidly.

Alginates↗