Water Content Determination of the Candidate Reference Material for Gliadin from European Wheat (IRMM-480)

The candidate reference material IRMM-480 was produced in co-operation with the Working Group on Prolamin Analysis and Toxicity (WGPAT) and is currently being investigated within the framework of certification involving homogeneity, stability and value assignment studies. The material was prepared as an extract from 28 selected, representative wheat varieties and underwent two freeze-drying steps in order to reduce its water content and to stabilise the material. In former studies the material was found to be very hygroscopic (1-3). Rapid uptake of water made it important to introduce an appropriate handling procedure as dry mass correction is practically ruled out due to low total mass and the use of this RM by laboratories, which specialize in immunoassay procedures. As the water content is of pivotal importance for the characterisation, monitoring and the use of the material, as well as for its suitability for the testing purpose, an appropriate, quantitative method for water determination is required, which is rapid and precludes further water uptake during sample preparation. The application of common methods such as direct oven drying was not feasible due to the small quantities of gliadin per vial (~ 100 mg) and the low water content of approximately 1 g/100 g. Direct volumetric and direct coulometric Karl Fischer titration (C-KFT) also did not lead to useful results, due to precipitation of the material on the electrodes. Therefore, our strategy was to develop a new method for water content determination, using an oven sample processor (OSP) connected to a titration cell of a Karl-Fischer coulometer, which would be appropriate for low sample amounts of crystalline dry powders combined with suitable sensitivity. In this publication, the new method is described and results from the water content determination of IRMM-480 are presented. Further, a procedure for the proper handling of this material is also given.

BERNREUTHER Alexander;  KLEIN Christoph; 

2006-01-19

Verlag Wissenschaftliche Scripten 2005

JRC30284