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Evaluation of charge measurements using streaming potential titration
Team Leader: Simona Strnad (University of Maribor, Slovenia)
Abstract:
The charge of cellulosic materials gained through dissociation of surface groups (mainly carboxyl and hydroxyl functions) is an essential feature of their chemical and physical properties. The dissociated groups have a strong influence on the nature of adsorption (chemical or physical) as well as on the adsorption kinetics of components present in the liquid phase, such as surfactants, dyes, polyelectrolytes, proteins, coating materials etc. One important method for charge evaluation, coming from the field of colloid chemistry, is particle charge titration using streaming potential measurement for end point determination.
Aim of this round robin test is the introduction and evaluation of standardised methods for the charge determination of soluble polyelectrolytes and solid cellulosic material using particle charge titration. The evaluated method then will serve as a standard tool for charge determination within the research network, providing fully comparable results coming from different laboratories.
Objectives:
Selection of cationic and anionic surfactants/polyelectrolytes serving as standard titration substances.
Selection of samples from polyelectrolytes and cellulosic fibres for titration.
Preparation of procedures for sample preparation, titration and cleaning procedures.
Evaluation of the procedures regarding practicability.
Distribution of samples and standard substances to the participating partner institutions.
Statistical assessment and comparison of the results.
Based on the results, setup of reproducible standard methods for charge determination, revision of current methods to reach best comparability.
Considerations on further advanced charge determination procedures.
One of the main tasks, which have to be fulfilled in the frame of the Fundamental Theme 5 is the characterisation of the surface properties of modified polysaccharide surfaces. The presented standardisation project will provide important information about the measuring and characterisation procedures of surface charge determination for fibre samples. Measuring protocols will allow comparable monitoring as also high level of reproducibility of measuring results. This standardisation project provides the basis for the unambiguous determination and interpretation of polysaccharide surface properties.
Importance for EPNOE community and industrial partners:
A standardised method for charge determination of polysaccharide materials will provide a tool for the characterisation of polysaccharide materials useful for all EPNOE Partners. The determination of accessible surface charges and the total charge of the polysaccharide material is an inevitable parameter for the steering and understanding of polysaccharide interactions with charged molecules. These Coulomb interactions become more and more important in the processing of polysaccharide materials, regarding the preferential reduction of salt and additives in the processing baths due to environmental reasons. This directly addresses the needs of industrial partners in an effective and reliable control of interaction parameters occurring in modern wet-state processing of polysaccharide materials. Charge determination is one of the methods of choice concerning these requirements.
Importance for the characterisation of the polysaccharide raw materials:
The charge of raw materials can serve on one hand as a factor for the quality assurance in production processes. On the other hand, fundamental interaction properties of the material can be elucidated by the determination of the surface and total charge of polysaccharide materials.
Importance for the characterisation of polysaccharide processability:
In many wet-state processing steps of polysaccharides, the material has to interact with charged molecules in the surrounding solution, e.g. surfactants, polyelectrolytes, dyes. The electrostatic interactions in these processing steps become of more importance, especially in solutions with reduced ionic strength. Therefore, for accurate control of the processability, parameters like charge and charge distribution within the polysaccharide material have to be known. This has to be considered in the design and conduction of polysaccharide processing methods.
Applicability to the different kind of polysaccharides:
The method of charge titration is in principle applicable to all kinds of polysaccharide materials, directly for soluble systems and using an indirect approach, also for non-soluble polysaccharide materials.
Potentiality to transform them into marketable products:
The standardised method of charge determination can in future be offered as a service to companies and research groups working in the field of processing polysaccharide materials.