The CCQM-K78.b comparison was coordinated by the BIPM on behalf of the CCQM Organic Analysis Working Group (OAWG) for NMIs and DIs which provide measurement services in organic analysis under the CIPM MRA. The key comparison forms part of the current OAWG 10-year strategic plan of comparisons. CCQM-K78.b underpins capabilities for value assignment of calibration solutions consisting of low polarity/non-polar organic analytes in organic solvent. The model system selected was a two component pesticide solution in acetonitrile. Participants were required to assign the mass fractions, expressed in units of μg/g, of methoxychlor (M) and trifluralin (T) in solution in acetonitrile (ACN). The content and analytical challenges of the selected analytes are representative of those for calibration solutions for non-polar organic analytes in solution. Participation in CCQM-K78.b benchmarked capability for assigning the content of non-polar organic compounds (pKow < -2) in solution at a mass fraction range above 5 μg/g in an organic solvent. It also tested capabilities for the quantitative assignment of thermally labile compounds.