/ Research / Experimental se... / Carboxyl Groups
Correlation between the amounts of carboxyl groups determined by chemical, titration methods and the surface charge/total charge
Team Leader: Paul Kosma (University of Natural Resources and Applied Life Sciences, Austria)
Abstract:
The aim of the round robin is to evaluate chemical and physical methods to determine acidic groups in cellulosic substrates. Such substrates may be cellulosic fibers and pulp (bleached and unbleached, paper and dissolving grade).
Within the chemical characterization different methods for the determination of carboxyl groups will be compared. Classical approaches, such as the methylene blue technique will be judged against novel approaches such as the FDAM technique of fluorescence labeling in combination with GPC. To obtain further details on the chemical nature of acidic groups hexenuronic acids in pulp samples can be determined. Different methods for HexA quantification are available (data from Round Robin carbohydrate composition in solid materials should be utilized here as well, possibly also one substrate used in this round robin).
The data are related to the results obtained by physical means such as zeta-potential measurements, electrokinetic potential and total and surface charge measurements.
Objectives:
Access to a reliable and advanced methodology for the determination of acidic groups is central to many EPNOE activities. So far most of the published methods lack sensitivity and reproducibility and are thus of limited use. In particular, characterization of raw materials, which contain acidic groups in small amounts is required to better understand and monitor process behavior. Moreover, functionalization of many polysaccharides involves the non-covalent or covalent incorporation of acidic groups which strongly contribute to the final product properties. Hence, projects in Fundamental Theme 3, Fundamental Theme 4 (explicitly describing synthesis of anionic polysaccharide derivatives), Fundamental Theme 5 and Fundamental Theme 6 can be directly linked to this tool.
Importance for EPNOE community and industrial partners:
For the first time chemical and physical methods for the determination of acidic groups will be compared. This will form the basis to evaluate the scope of available as well as novel methodologies and will also define the application fields of the individual techniques. A thorough analysis and cross-validation of the determination of acidic groups will be of prime interest to EPNOE and industrial partners working with various polysaccharides and polysaccharide derivatives (examples: analysis of acidic hemicellulose fractions contributing to paper fibre strength, ionic interactions to be used for reassembly of different polysaccharides or polysaccharide-polymer blends, surface modification of polysaccharides, carboxymethyl derivatives, oxidized polysaccharides for medical and other applications, selective derivatization for introduction of anchor groups to serve for tailor-made applications such as controlled-drug release or crosslinking of polysaccharides).
Importance for the characterisation of the polysaccharide raw materials:
Acid groups are a major characteristic of many different types of polysaccharides (cellulose associated. with hemicelluloses, hemicelluloses, pectins, chitosans). Comprehensive data on acidic groups provides better knowledge on structural characterization as well as processability.
Importance for the characterisation of polysaccharide processability:
Carboxyl groups contribute to various process-related properties such as alkali resistance, relationship with metal and water binding properties, aging, bleaching and dyeing chemistry.
Applicability to the different kind of polysaccharides:
Round robin study will be done on pulp and fiber, other polysaccharides are possible (e.g. hemicelluloses) as well as polysaccharide derivatives (e.g. TEMPO-oxidized polysaccharide)
Potentiality to transform them into marketable products:
The outcome of this project will be of importance towards a better understanding of charged groups in polysaccharides for multiple exploitation in product development. Analytical service can late on be offered to industrial partners.