This document specifies a method for the quantitative determination of monomeric diisocyanate content in coating materials, adhesives and other liquid or pasty materials. This method is suitable for the quantification of the following monomeric diisocyanates: methylene diphenyl diisocyanate (MDI, 2,4 -MDI and 4,4 -MDI), toluene diisocyanate (TDI, 2,6-TDI, 2,4-TDI), (cis/trans) isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI,1,6-HDI) in various matrices for concentrations ranging from 0,01 % to 2,0 % mass fraction. For higher concentrations, a suitable dilution before the derivatization with p-nitrobenzyl-N-propylamine (PNBPA) is performed. The measurements are carried out using ultra high performance liquid chromatography (UHPLC) with a multiple wavelength detector.