Full Description ADOPTED_FROM:EN ISO 21253-2:2019 This document specifies the criteria for developing an in-house mass spectrometry-based method for quantitative analysis of multiple subgroups of organic substances in the scope of physical-chemical analysis of water. This document supplements ISO/TS 13530 which provides guidance on the initial characterization of the measurement performances, by providing details to select the test matrix and internal standards and criteria for analyte and internal standard recoveries. This document is not intended as a substitute for the currently applicable analytical standards dedicated to organic compounds but as a resource bringing additional characterization elements.