Preparation and certification of three new aluminum alloy reference materials using inter-laboratory comparison approach

Abstract

Accuracy and comparability of measurement results are vital to guarantee correct controlled measurement process and operational conditions. All of these require reliable measurements based on reference materials whose certified values must be gotten by dependable metrological approaches agreeing to the requirements of ISO/ICE 17034 and ISO guide 35 (ISO, 2016; Guide, 2017).The metrological characteristics of certified reference materials (CRMs), especially the uncertainty of their properties, and the position within the traceability hierarchy are items of interest for quality assurance. CRMs play a key role in the quality control, precision studies, verification and validation of test methods. Comparability and the accuracy of the measurement results depend strongly on the availability of certified reference materials appropriate for a specific application. Within the present work, different aluminum alloys reference materials were produced by the National Institute of Standards (NIS), Egypt. Homogeneity of the produced reference materials (RMs) was studied by spark emission spectrometer (AES) and therefore, the results revealed that the produced RMs were homogeneous to disseminate the traceability through the calibration process. Also, they are useful to be used as internal quality control samples to evolve that different products meet required specification. The characterization process of the produced reference materials composition was performed by different independent analytical methods; XRF, Atomic emission spectrometer, inductively coupled plasma- optical emission spectrometer and atomic absorption spectrometry in several laboratories. The statistical data processing, and the data combining in the characterization step is the most important step of reference materials production process. Several methods are used to assign the certified value and its uncertainty such as the robust mean, the weighted mean approaches. The use of inter-laboratory comparison results for reference material certification is very common. In the present study, the assigned values of the mass fractions of the varied elements of the alloys and their uncertainty were calculated by applying the weighted mean approach to inter-laboratory comparison results collected.