Method-defined parameters: measurands sometimes forgotten

The main purpose of this article is to systematize and to describe method-defined parameters (MDPs) as non-conventional analytical results. MDPs depend on the methods that provide them, not on measurement standards. They are of great practical relevance because they are increasingly used in routine laboratories. There is a need to adapt the metrological approach in chemistry to their peculiar analytical characteristics. In this way, accreditation processes in analytical laboratories could be facilitated, taking into account the need for simple, reliable methods to process quickly large numbers of samples each day.