Ensuring the Validity of the Results by Participating in ILC Schemes—Case Study: The Determination of the Water-Soluble Chromium (VI) Content of Cement

The paper presents the mode in which an accredited laboratory, according to SR EN ISO/IEC 17025, monitors its performance by comparing the results with the results of other laboratories. This article aims to analyse the results of the participation of an accredited laboratory in two ILC schemes, one organized in France and the other in Romania, on cement, discussing only the results of the determinations of the water-soluble hexavalent chromium content. Although chromium (VI) is not present in large amounts in cement, it is responsible for allergic reactions on the skin of workers. Thus, in EU countries, the maximum amount of water-soluble Cr (VI) in bagged cement or in the products based on cement is limited to a maximum of 0.0002% by mass of cement. The Chromium (VI) results obtained by the lab must meet the requirements of the standard SR EN 196-10 for the repeatability and, where appropriate, the reproducibility. Questions about the validity of the results arise when the laboratory obtains satisfactory results in the ILC scheme, but the standard deviation of the scheme is higher than that recommended in the standard method. The elements of the novelty of this paper are the interpretation of water-soluble Cr (VI) results and the use of information obtained from participating in interlaboratory testing schemes tom improve the validity of laboratory results.