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Applied Colloids Surfactants
ACHEMA 2006 - Exhibition and Presentations
PARTEC 2004/2007 - International Conference for Particle Technology
CESIO 2004 - 6th World Surfactants Congress
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PARTEC 2007 - International Conference for Particle Technology
27-29 March Nuremberg, Germany
Conference Contributions
Particle interactions in dispersions of micro and nanoparticles / Sedimentation of Colloidal Particles
Characterization of liquid nanoparticle dispersions by multisample analytical centrifugation
Characterization of carbon black dispersions by multisample analytical centrifugation
Separation behaviour and dispersion properties of clay suspensions traced by multisample analytical centrifugation
Evaluation of Particle Size Analysis by Novel
Centrifugal Sedimentation Method
A Novel Simulation Method for Separation Processes in Gravitational and Centrifugal Field
ACHEMA 2006
15 - 19 May 2003 Frankfurt am Main
for general information see
ACHEMA 2006 - 28. Internationaler Ausstellungskongreß
Multisample Instruments for characterization of dispersions - for further information see
http://www.lum-gmbh.com
PARTEC 2004 - International Conference for Particle Technology
16 - 18 March Nuremberg, Germany
Thank you for fruitful discussions at POWTECH/PARTEC
CESIO 2004 - 6th World Surfactants Congress
20 - 23 June Berlin, Germany
Analytical centrifugation for emulsion characterization and additive selection
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Papers presented at ACHEMA 2006
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T. Sobisch* and D. Lerche, Berlin/Germany
Application of multisample analytical centrifugation for evaluation of stability of cosmetic products
The development of personal care products as well as process development/monitoring and quality assurance require efficient and objective analytical tools for shelf life prediction and stability determination. To this end the potential of multisample analytical centrifugation was evaluated as an accelerated test procedure.
A new multisample approach is presented using analytical centrifugation (STEP-Technology), which allows for an accelerated characterization of destabilization processes (creaming, sedimentation, coalescence, phase separation). The kinetics of these destabilizing processes can be traced simultaneously for up-to 12 different samples with temperature control in the range between 4 and 45 °C.
Analytical centrifugation measures in a rapid way the inherent stability of the samples. Alterations due to chemical reactions or similar processes may be investigated, combining first a shorted common accelerated stability test and second a rapid evaluation by analytical centrifugation.
The wide application potential of this approach is demonstrated by examples of measurements on lotions, shampoos, sun creams, creams of oil-in-water and water-in-oil type. Results will be compared with common accelerated aging tests and long term stability.
Keywords
Analytical Centrifugation; Dispersions; Emulsions; Separation Stability; Destabilization Kinetics, Accelerated Aging
Lerche, D.; Sobisch, T.; Küchler, S.; Uhl, A.
Rapid stability assessment for liquid and semi-liquid foods with multisample analytical centrifugation
A considerable fraction of food products are dispersions (emulsions, suspensions, suspoemulsions). Therefore not only the microbiological and chemical stability matters, but the demixing and structural stability has to be taken into account for the formulation of new products as well as in process monitoring and quality assurance of the production process. These requires efficient and objective analytical tools for shelf life prediction and stability determination.
A new multisample approach is presented using analytical centrifugation, which allows for an accelerated and rapid characterization of the demixing behaviour (creaming, sedimentation, coalescence, phase separation) of dispersions without dilution. By means of a STEP-technology, space and time resolved extinction profiles quantify the alteration of particle concentration due to the demixing phenomena over the entire sample height during the centrifugation. The kinetics can be traced simultaneously for up-to 12 different samples in a temperature-controlled way between 4 °C and 45 °C.
The wide application potential of this approach is demonstrated on typical food dispersions like milk and milk based products. We present results of the influence of the homogenisation process and the fat content on demixing stability and shelf life as well as on the water/whey retention of semi-liquid products like curd and yoghurt.
Supported by a grant of the BMWA (INNO-Watt)
Rapid evaluation of emulsion stability and demulsifier selection by analytical centrifugation
Chemistry Preprint Archive, Volume 2002, Issue 6, June 2002, Pages 195-201, Chemistry Preprint Archive, Volume 2004, Issue 5, May 2004, Pages 7-18
Rapid characterization of emulsions for emulsifier selection, quality control and evaluation of stability using multisample analytical centrifugation
recommended link
Emulsion Stability
Oral presentation at PARTEC 2004
Characterization of interparticle forces in dispersions by analytical centrifugation
Sobisch T.* and Lerche D., L.U.M. GmbH Berlin
The behaviour of dispersions in liquid media, i.e. dispersion stability, flow and packing behaviour and processes at the solid-liquid interface, is determined by the nature and degree of interparticle forces. This is of fundamental importance for their application in diverse fields such as nanomaterials, coating, paper making, ceramics, sludge dewatering, to name just a few.
The present work reports on the use of analytical centrifugation for investigation of the packing and compression behaviour to characterize the colloidal stability and microstructure in aqueous dispersed systems. To this end interactions have been studied in monodisperse silica dispersions and in dispersions of cellulose fibres.
Packing density, obtained after compression, is related to the total interparticle potential energy. By using different additives interaction between particles can be shifted from nearly hard sphere behaviour to strong attraction which results in flocculated systems. Both substrates differ in particle shape, swelling properties and surface charge density and exhibit therefore different packing behaviour. Additional information could be obtained about the strength and elasticity of particle networks by analysing the relative change in sediment volume after increasing/decreasing the excess pressure.
The multisample technique applied implies the potential for more systematic studies for targeted colloidal stability.
Papers presented at CESIO 2004
Analytical centrifugation as efficient tool for selection of additives, their optimum concentration and composition
D. Lerche, T. Sobisch
Surface active additives are often applied to stabilize dispersions (emulsions, suspensions) and to modify surface properties. Selection of optimum additive concentration and composition is a crucial step in formulation and in design of technical applications. To this end, a lot of different laboratory methods have been developed, which are in part very sophisticated or on the other end may be very simple but strongly based on individual judgement and experience.
Up-to-date related investigations often require a lot of manpower without delivering clear-cut results.
A multisample technique based on analytical centrifugation is presented which allows for an accelerated study of dispersion stability, separation velocity and packing density without dilution, thus avoiding changes of dispersion properties. The kinetics of separation are measured directly in-situ with high time and space resolution. The latter is of great practical importance for estimation of shelf life and in relation to the engineering of separation processes. Results measured are definitely related to the functional properties to obtain.
Several examples are compiled which demonstrate the efficiency of the method proposed for screening and in-depth studies.
These include additive selection for soil dispersion, lime stabilization und surface modification. Results are compared with investigations at normal gravity using a device with photometric detection.
Supported by BMWT: Grant 1049/02
Lumifuge-Application Testing Stabilization of carbon black dispersions Part I
Lumifuge-Application Testing Stabilization of carbon black dispersions Part II
Selection of lime dispersing agents by multisample analytical centrifugation
Rapid emulsifier selection and evaluation of emulsion stability by analytical centrifugation
T. Sobisch, D. Lerche
Selection of emulsifiers and evaluation of emulsion stability is a frequent task. This relates to practical issues like formulation of emulsions, optimization of preparation conditions, quality control, shelf life estimation and breaking of emulsions.
A multisample technique based on analytical centrifugation is presented which allows for an accelerated study of creaming and of separation of oil and water phases. Not only information on the extent of phase separation is provided but also the kinetics are directly measured in-situ. The latter is of great practical importance for estimation of shelf life and in relation to the engineering of separation processes.
Results of investigations on emulsion stability behaviour as function of polarity of nonionic emulsifiers, polarity of the oil phase, preparation conditions and of temperature are presented.
The investigations revealed that the method applied is very suitable for screening purposes and that time of investigation and centrifugal acceleration can be adapted to avoid conditions were centrifugal forces are the determining factor for phase separation.
Supported by BMWT: Grant 1049/02
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