This document specifies a method for determining the total content of the following cyclosiloxanes in waterproofing fatliquors and other silicone-based chemicals for the leather tanning industry: octamethylcyclotetrasiloxane (D4); decamethylcyclopentasiloxane (D5); dodecamethylcyclohexasiloxane (D6); This method requires the use of liquid chromatography (GC) equipped with a single quadrupole mass spectrometer (MS) to identify and quantify the cyclosiloxanes.