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Jouko Yliruusi - One of the best experts on this subject based on the ideXlab platform.
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the behavior of Sorbitan surfactants at the water oil interface straight chained hydrocarbons from pentane to dodecane as an oil phase
Journal of Colloid and Interface Science, 2001Co-Authors: Leena Peltonen, Jouni Hirvonen, Jouko YliruusiAbstract:The interfacial tension of four Sorbitan surfactants (Span 20, Sorbitan monolaurate; Span 40, Sorbitan monopalmitate; Span 60, Sorbitan monostearate; and Span 80, Sorbitan monooleate) was determined at the water-oil interface. Seven straight-chained hydrocarbons from pentane to dodecane were used as an oil phase. From the interfacial tension measurements the following values were calculated: critical micelle concentration (cmc), the interfacial tension at the cmc (gamma(cmc)), surface pressure at the cmc (pi(cmc)), area per molecule at the cmc (A(cmc)), standard free energy of micellization (DeltaG degrees (mic)), and standard free energy of adsorption (DeltaG degrees (ad)). The shorter chained Span 20 and unsaturated Span 80 had higher cmc values and Span 80 had a larger molecular area than the other surfactants. With the same oil phase, differences between pi(cmc) values of the four Sorbitan monoesters were small, but the gamma(cmc) was slightly lowered as the hydrophobicity of the surfactant was increased. DeltaG degrees (mic) was less negative for Span 20 and the DeltaG degrees (ad) value was slightly more negative for Span 80. The effect of the oil phase was obvious. Increasing the hydrocarbon chain length of the oil phase increased gamma(cmc) and cmc values while pi(cmc) and A(cmc) were decreased. As the length of the hydrocarbon chain of the oil phase was increased, DeltaG degrees (mic) and DeltaG degrees (ad) became less negative, which means a less spontaneous reaction. Copyright 2001 Academic Press.
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the behavior of Sorbitan surfactants at the water oil interface straight chained hydrocarbons from pentane to dodecane as an oil phase
Journal of Colloid and Interface Science, 2001Co-Authors: Leena Peltone, Jouni Hirvone, Jouko YliruusiAbstract:Abstract The interfacial tension of four Sorbitan surfactants (Span 20, Sorbitan monolaurate; Span 40, Sorbitan monopalmitate; Span 60, Sorbitan monostearate; and Span 80, Sorbitan monooleate) was determined at the water–oil interface. Seven straight-chained hydrocarbons from pentane to dodecane were used as an oil phase. From the interfacial tension measurements the following values were calculated: critical micelle concentration (cmc), the interfacial tension at the cmc (γcmc), surface pressure at the cmc (πcmc), area per molecule at the cmc (Acmc), standard free energy of micellization (ΔG°mic), and standard free energy of adsorption (ΔG°ad). The shorter chained Span 20 and unsaturated Span 80 had higher cmc values and Span 80 had a larger molecular area than the other surfactants. With the same oil phase, differences between πcmc values of the four Sorbitan monoesters were small, but the γcmc was slightly lowered as the hydrophobicity of the surfactant was increased. ΔG°mic was less negative for Span 20 and the ΔG°ad value was slightly more negative for Span 80. The effect of the oil phase was obvious. Increasing the hydrocarbon chain length of the oil phase increased γcmc and cmc values while πcmc and Acmc were decreased. As the length of the hydrocarbon chain of the oil phase was increased, ΔG°mic and ΔG°ad became less negative, which means a less spontaneous reaction.
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surface pressure hysteresis interfacial tension and cmc of four Sorbitan monoesters at water air water hexane and hexane air interfaces
Journal of Colloid and Interface Science, 2000Co-Authors: Leena Peltonen, Jouko YliruusiAbstract:Abstract The purpose of this study was to investigate the interfacial properties of Sorbitan monoesters (Span 20, 40, 60, and 80). The surface pressure was investigated at the water–air interface using a Langmuir–Blodgett apparatus. Interfacial tensions at n -hexane–air and water– n –hexane interfaces were measured by a du Nouy tensiometer. The effects of different surface-active agents and their concentrations on the interfacial properties of surfactant films were determined. With saturated Sorbitan monoesters the lengthening of the hydrocarbon chain increases the collapse pressure and molecular area at the water–air interface. Unsaturated Span 80 had a lower collapse pressure and a larger molecular area than its saturated counterpart Span 60. Under compression–expansion cycles, all Sorbitan monoesters showed hysteresis effects. At the n -hexane–air interface there were no differences in the interfacial tension between different Sorbitan monoesters. At the water– n -hexane interface, differences in CMCs were small, but the surface excess of Span 80 was markedly smaller and the molecular area larger than the corresponding values of other Sorbitan monoesters.
Leena Peltonen - One of the best experts on this subject based on the ideXlab platform.
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Opponent:
2014Co-Authors: Leena Peltonen, Professor Jouko YliruusiAbstract:the bulk properties of these surfactants as a function of temperature. Dissertationes Biocentri Viikki Universitatis Helsingiensis 8/2001, pp. 42. ISBN 952-10-0005-8 (print) ISBN 952-10-0006-6 (pdf) ISSN 1239-9469 The aims of this study were to determine the structural effects of both the hydrocarbon chain structure of the Sorbitan surfactants and of the oil phase hydrocarbon on the interfacial behaviour of these surfactants. The effect of molecular structure of surface-active agents on the interfacial phenomena in emulsions and other pharmaceuticals is an area of current interest. Many important processes and products are based on the fundamental interactions occurring in this interfacial area. For example, the stability of particle dispersions, emulsions, and a number of other pharmaceutical product forms depend on the stability of the interfacial films within these systems. In this study, the interfacial behaviour of Sorbitan surfactants with different alkyl chain structures (Sorbitan monolaurate, Span 20, Sorbitan monopalmitate, Span 40, Sorbitan monostearate, Span 60, and Sorbitan monooleate, Span 80) at liquid-air
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the behavior of Sorbitan surfactants at the water oil interface straight chained hydrocarbons from pentane to dodecane as an oil phase
Journal of Colloid and Interface Science, 2001Co-Authors: Leena Peltonen, Jouni Hirvonen, Jouko YliruusiAbstract:The interfacial tension of four Sorbitan surfactants (Span 20, Sorbitan monolaurate; Span 40, Sorbitan monopalmitate; Span 60, Sorbitan monostearate; and Span 80, Sorbitan monooleate) was determined at the water-oil interface. Seven straight-chained hydrocarbons from pentane to dodecane were used as an oil phase. From the interfacial tension measurements the following values were calculated: critical micelle concentration (cmc), the interfacial tension at the cmc (gamma(cmc)), surface pressure at the cmc (pi(cmc)), area per molecule at the cmc (A(cmc)), standard free energy of micellization (DeltaG degrees (mic)), and standard free energy of adsorption (DeltaG degrees (ad)). The shorter chained Span 20 and unsaturated Span 80 had higher cmc values and Span 80 had a larger molecular area than the other surfactants. With the same oil phase, differences between pi(cmc) values of the four Sorbitan monoesters were small, but the gamma(cmc) was slightly lowered as the hydrophobicity of the surfactant was increased. DeltaG degrees (mic) was less negative for Span 20 and the DeltaG degrees (ad) value was slightly more negative for Span 80. The effect of the oil phase was obvious. Increasing the hydrocarbon chain length of the oil phase increased gamma(cmc) and cmc values while pi(cmc) and A(cmc) were decreased. As the length of the hydrocarbon chain of the oil phase was increased, DeltaG degrees (mic) and DeltaG degrees (ad) became less negative, which means a less spontaneous reaction. Copyright 2001 Academic Press.
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surface pressure hysteresis interfacial tension and cmc of four Sorbitan monoesters at water air water hexane and hexane air interfaces
Journal of Colloid and Interface Science, 2000Co-Authors: Leena Peltonen, Jouko YliruusiAbstract:Abstract The purpose of this study was to investigate the interfacial properties of Sorbitan monoesters (Span 20, 40, 60, and 80). The surface pressure was investigated at the water–air interface using a Langmuir–Blodgett apparatus. Interfacial tensions at n -hexane–air and water– n –hexane interfaces were measured by a du Nouy tensiometer. The effects of different surface-active agents and their concentrations on the interfacial properties of surfactant films were determined. With saturated Sorbitan monoesters the lengthening of the hydrocarbon chain increases the collapse pressure and molecular area at the water–air interface. Unsaturated Span 80 had a lower collapse pressure and a larger molecular area than its saturated counterpart Span 60. Under compression–expansion cycles, all Sorbitan monoesters showed hysteresis effects. At the n -hexane–air interface there were no differences in the interfacial tension between different Sorbitan monoesters. At the water– n -hexane interface, differences in CMCs were small, but the surface excess of Span 80 was markedly smaller and the molecular area larger than the corresponding values of other Sorbitan monoesters.
Marian Wlodzimierz Sulek - One of the best experts on this subject based on the ideXlab platform.
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paraffin oil solutions of the mixture of Sorbitan monolaurate ethoxylated Sorbitan monolaurate as lubricants
Wear, 2006Co-Authors: Tomasz Wasilewski, Marian Wlodzimierz SulekAbstract:Abstract Paraffin mixtures of Sorbitan monolaurate (SML)–ethoxylated Sorbitan monolaurate (ESML) were applied as lubricant additives. The esters tested can be obtained from natural resources. They are environment-friendly. Tests under steady load conditions were performed to assess their tribological properties. The friction coefficient and wear scar diameter were measured. On the basis of the results obtained one can conclude that the mixtures tested significantly reduce motion resistance and wear. As compared to paraffin oil, wear scar diameter was reduced four times, while friction coefficient—even six times. The influence of total concentration and SML:ESML ratio on tribological properties was analyzed. The synergistic effect, attaining its optimum for comparable mole fraction of both esters, was observed. The results can be interpreted in terms of creation of micellar solutions and interaction of these structures with friction surface.
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paraffin oil solutions of the mixture of Sorbitan monolaurate ethoxylated Sorbitan monolaurate as lubricants
Wear, 2006Co-Authors: Tomasz Wasilewski, Marian Wlodzimierz SulekAbstract:Abstract Paraffin mixtures of Sorbitan monolaurate (SML)–ethoxylated Sorbitan monolaurate (ESML) were applied as lubricant additives. The esters tested can be obtained from natural resources. They are environment-friendly. Tests under steady load conditions were performed to assess their tribological properties. The friction coefficient and wear scar diameter were measured. On the basis of the results obtained one can conclude that the mixtures tested significantly reduce motion resistance and wear. As compared to paraffin oil, wear scar diameter was reduced four times, while friction coefficient—even six times. The influence of total concentration and SML:ESML ratio on tribological properties was analyzed. The synergistic effect, attaining its optimum for comparable mole fraction of both esters, was observed. The results can be interpreted in terms of creation of micellar solutions and interaction of these structures with friction surface.
Alexander T. Florence - One of the best experts on this subject based on the ideXlab platform.
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inverse toroidal vesicles precursors of tubules in Sorbitan monostearate organogels
International Journal of Pharmaceutics, 1999Co-Authors: Sudaxshina Murda, Gregory Gregoriadis, Alexander T. FlorenceAbstract:Sorbitan monostearate organogels are opaque, thermoreversible semi-solids whose microstructure consists of surfactant tubules dispersed in the organic continuous phase. Inverse toroidal vesicles are the precursors of the surfactant tubules. The gelation process was observed as an isotropic sol phase of Sorbitan monostearate in isopropyl myristate was cooled using hot-stage light microscopy. At the gelation temperature, inverse toroidal vesicular structures were seen to grow in the organic phase. These toroids are thought to be analogous to other well-known vesicles, liposomes and niosomes, except for their toroidal (rather than spherical) shape and their inverse nature. They are rather short-lived structures: on further cooling of the sol phase, tubules form in the organic medium: it is speculated that the toroids elongate into tubular shapes or split into rod-shaped segments.
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novel Sorbitan monostearate organogels
Journal of Pharmaceutical Sciences, 1999Co-Authors: Sudaxshina Murda, Gregory Gregoriadis, Alexander T. FlorenceAbstract:Sorbitan monostearate, a hydrophobic nonionic surfactant, gels a number of organic solvents such as hexadecane, isopropyl myristate, and a range of vegetable oils. Gelation is achieved by dissolving/dispersing the organogelator in hot solvent to produce an organic solution/dispersion, which, on cooling sets to the gel state. Cooling the solution/dispersion causes a decrease in the solvent–gelator affinities, such that at the gelation temperature, the surfactant molecules self-assemble into toroidal inverse vesicles. Further cooling results in the conversion of the toroids into rod-shaped tubules. Once formed, the tubules associate with others, and a three-dimensional network is formed which immobilizes the solvent. An organogel is thus formed. Sorbitan monostearate gels are opaque, thermoreversible semisolids, and they are stable at room temperature for weeks. The gels are affected by the presence of additives such as the hydrophilic surfactant, polysorbate 20, which improves gel stability and alters the gel microstructure from a network of individual tubules to star-shaped “clusters” of tubules in the liquid continuous phase. Another solid monoester in the Sorbitan ester family, Sorbitan monopalmitate, also gels organic solvents to give opaque, thermoreversible semisolids. Like Sorbitan monostearate gels, the microstructure of the palmitate gels comprise an interconnected network of rodlike tubules. Unlike the stearate gels, however, the addition of small amounts of a polysorbate monoester causes a large increase in tubular length instead of the “clustering effect” seen in stearate gels. The Sorbitan stearate and palmitate organogels may have potential applications as delivery vehicles for drugs and antigens.
Taylor Zhang - One of the best experts on this subject based on the ideXlab platform.
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Mixed-mode and reversed-phase liquid chromatography-tandem mass spectrometry methodologies to study composition and base hydrolysis of polysorbate 20 and 80.
Journal of Chromatography A, 2010Co-Authors: Daniel Hewitt, Melissa Alvarez, Kathryn Robinson, Junyan Ji, Y. John Wang, Taylor ZhangAbstract:Abstract Polysorbate 20 (polyoxyethyleneSorbitan monolaurate) and polysorbate 80 (polyoxyethyleneSorbitan monooleate) used in protein drug formulations are complex mixtures that have been difficult to characterize. Here, two HPLC methods are used with evaporative light scattering detection (ELSD) and mass spectrometry (MS) to characterize polysorbate from commercial vendors. The first HPLC method used a mixed-mode stationary phase (Waters Oasis MAX, mixed-mode anion exchange and reversed-phase sorbent) with a step gradient to quantify both the total polyoxyethylene Sorbitan ester and polyoxyethylene Sorbitan (POE Sorbitan, a non-surfactant) in polysorbate. The results indicated POE Sorbitan was present from 16.0 to 27.6 and 11.1 to 14.5% (w/w) in polysorbate 20 and 80, respectively. The second HPLC method used a reversed-phase stationary phase (Zorbax SB-300 C8) with a shallow gradient to separate, identify, and quantify the multiple ester species present in polysorbate. For all lots of polysorbate 20 analyzed, only 18–23% of the material was the expected structure, polyoxyethyleneSorbitan monolaurate. Up to 40% and 70% (w/w) di- and triesters were found in polysorbate 20 and polysorbate 80 respectively. Likewise, polyoxyethyleneSorbitan monooleate accounted for only 20% of polysorbate 80. A variability of 3–5% was observed for each ester species between multiple lots of polysorbate 20. The reversed-phase method was then used to determine the rate of hydrolysis for each polyoxyethylene Sorbitan ester of polysorbate 20 in basic solution at room temperature. Increasing rates of hydrolysis were observed with decreasing aliphatic chain lengths in polysorbate 20.
