New matrix-free reference material for ethene in the form of optical fibres.

Reference materials are indispensable in the quality control and quality assurance of analytical measurements. One novel approach to the generation of standard gaseous mixtures of toxic, reactive, volatile, labile, and malodorous substances involves thermal decomposition or rearrangement, under defined temperature conditions, of compounds immobilized, by chemical bonding, on the surface of an appropriate carrier to release specific amounts of a volatile compound. In this technique the type of support used to immobilize the compound is extremely important, because the amount of analyte released depends directly on the choice of material. In this paper we report the novel preparation of a matrix-free ethene standard in the form of glass fibres coated with a thin layer of aluminium, the surface of which is modified by reaction with a specific compound. As a result of thermal decomposition of this compound, gaseous ethene is formed. In this paper we present the results obtained from tests of stability and homogeneity, two properties of crucial importance in the preparation of reference materials, by comparison of a series of results obtained for randomly chosen samples of the reference material. Interlaboratory comparative studies resulted in determination of a reference value for the ethene formed after thermal decomposition of the surface compound ((2.12 ± 0.14) ng per fibre).