This document is a method for determining ethoxylated alkylphenols (APEO) [nonyphenol ethoxylate (NPEO_n, where 2 ≤ n ≤ 16) and octylphenol ethoxylate (OPEO_n, where 2 ≤ n ≤ 16)] in leather. This direct method is especially suitable when a larger number of leather samples are to be checked for the presence of ethoxylated alkylphenols.

This method requires the use of liquid chromatography (LC) with a triple quadrupole mass spectrometer (MS/MS) to identify and quantify the ethoxylated alkylphenols.

NOTE 1        In the leather industry, the most commonly used ethoxylated alkylphenol is 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        This document and ISO 18218-2 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.