This document is a method for determining ethoxylated alkylphenols (nonyphenol ethoxylate [NPEOn with 1 d" n d" 16] and octylphenol ethoxylate [OPEOn with 1 d" n d" 16]) in leather. This direct method is especially suitable where a larger number of leather samples are to be checked for the presence of ethoxylated alkylphenols. This method requires the use of high-performance liquid chromatography (HPLC) with triple quadrupole mass spectrometer (MSMS) to identify and quantify the ethoxylated alkylphenols. NOTE 1 In the leather industry, the most commonly used commercial ethoxylated alkylphenol has been the NPEO with an average of 9 EO. It has an optimum cloud point in water for the typical leather processing temperatures of 40 °C to 55 °C. NOTE 2 ISO 18218-1 and ISO 18218-2[1] use different solvents for the extraction of the ethoxylated alkylphenols from leather. Consequently, the two analytical methods are expected to give similar trends but not necessarily the same absolute result for the ethoxylated alkylphenol content in leather.