GB/T 40323
Determination of octamethylcyclotetrasiloxane(D4), decamethylcyclopentasiloxane(D5) and dodecamethylcyclohexasiloxane(D6) in textile dyeing and finishing auxiliaries
A Chinese national standard test method. China produces more textiles than any other country, and a specification written there cites GB designations rather than ISO or ASTM ones.