Uncertainty and traceability in an assay method (ascorbic acid in juices)

We discus two of the most important aspects for ensuring the quality of the measurements in an assay method. These parameters are: measurement uncertainty and traceability of the measuring method. To be able to exemplify these parameters, we took as an example the measuring of ascorbic acid in commercial juices to clearly understand all the implicit metrological requirements in an assay method. To do this, it was necessary to meticulously analyze every step of the ascorbic acid measuring process via implementation of the practical application of the AOAC 967.21 Official Method for determining ascorbic acid, which is a titrimetric method based on the ISO 10012 norm. The uncertainty and traceability were studied and applied to control the process variability on the assay method. All this allows us to show the importance of implementing a measurement control system on an assay method, thus guaranteeing repeatable and traceable measurements, and ensuring that the measurements have been done accurately.