ISO 15064:2010 specifies methods for the measurement of toluene-2,6‑diisocyanate in mixtures of the 2,4- and 2,6‑isomers. Two methods based on infrared spectroscopy are required to give accurate results over a broad range of isomer concentrations. Method A is applicable to TDI samples containing 5 % to 95 % of the 2,6‑isomer. Method B is applicable to TDI samples containing 0 % to 5 % of the 2,6‑isomer. Both methods are based on the quantitative measurement of absorption bands arising from out-of-plane C–H deformation vibrations of the aromatic ring at 810 cm–1 and 782 cm–1.