Method validation by collaborative trial for the quantification of binary mixtures containing polyamide and a novel polypropylene/polyamide bicomponent fibre

Abstract

A method for the quantification of a novel polypropylene/polyamide bicomponent fibre in binary mixtures with polyamide was subjected to validation by collaborative trial. Considering the probable acceptance of the novel fibre in Europe, this method would allow market surveillance and antifraud controls needed for consumer protection. The aim of the study was to extend the scope of application of method 11 of Directive 96/73/EC. The method foresaw selective dissolution of the polyamide component using 75% m/m sulfuric acid at room temperature for 1 h. In order to ensure accurate quantification of the blends, two additional rinsings of the residue with the reagent used for the dissolution had to be included in the washing procedure of method 11. Following ISO 5725, a balanced uniform level test was performed, with the participation of seventeen European laboratories, on loop twisted carpet samples of three levels of concentration. The trueness was evaluated considering, as reference, data values obtained from manual separation. The bias varied from 0.06 to 0.49%. Repeatability and reproducibility limits were in the range 0.70–1.04% and 0.97–1.87%, respectively. In agreement with the members of the European Network of National Experts on Textile Labelling, the optimized method was judged fit-for-purpose and the reproducibility limit was established at 2%. Based on this study, the novel fibre can be inserted in the scope of application of method 11 as the insoluble component ( d factor 1.005) and polyamide as the soluble one, provided that modifications are adopted.