Silicone oil is made by catalytic polymerization of siloxane rings. Incomplete reaction will cause the silicone oil product to contain residual siloxane ring raw materials from the polymerization process. There is obvious controversy among countries on whether silicone rings belong to PBT substances. In June 2018, they were included in the SVHC list of substances of very high concern (also known as the candidate authorization list); in 2020, the EU restricted the use of D4 and D5 in rinse-off cosmetics according to the REACH regulation. Rinse-off cosmetics containing a concentration equal to or greater than 0.1% (w/w) of D4 or D5 shall not be put on the market. This regulation added restrictions on the listing of rinse-off cosmetics containing D6 and resident cosmetics containing these three substances in 2023. At the same time, the European Commission also intends to include D4 in the list of persistent organic pollutants (POPs) under the Stockholm Convention. If successful, it means that its existence in the polymer field and nature will be subject to more stringent restrictions.

Silicone oil has a large solubility in common organic solvents. When using solvent extraction gas chromatography or gas chromatography-mass spectrometry to analyze the residual D4, D5, and D6 in silicone oil, it is inevitable that a large amount of silicone oil will accumulate in the vaporization chamber, which will seriously affect the reproducibility and accuracy of the analysis results. At the same time, in order to reduce the volatility loss of D4, D5, and D6 during the experiment, the sealing of the test system must be ensured during the analysis process, and the intermediate links of sample processing need to be reduced. Therefore, headspace gas chromatography analysis technology is used to determine the residual amount of D4, D5, and D6 in silicone oil.

The main content of "Determination of the Residual Amount of Octamethylcyclotetrasiloxane (D4), Decamethylcyclopentasiloxane (D5), and Dodecamethylcyclohexasiloxane (D6) in Silicone Oil: Headspace Gas Chromatography" stipulates the test method for the residual amount of D4, D5, and D6 in silicone oil. The instrument equipment, reagents and materials, instrument analysis conditions, accuracy, precision, test report, etc. of the test method are specified in detail.