GB/T 32718-2024 "Determination of defoliant residues in cotton fibers" standard describes the use of high performance liquid chromatograph - Tandom mass spectrometer (HPLC-MS/MS) for the determination of defoliant residues in cotton fibers such as tiphenolone, thiotein, diuron, defoliant phosphorus, ethephon, amide cyclopropionate. This standard applies to the accurate determination of defoliant residues in cotton fibers. The standard cites GB/T 6682 "Specifications and test methods for water used in analytical laboratories" as a normative reference document. The term definition includes the description of defoliant, that is, a chemical substance used to spray before cotton harvest to induce peeling of cotton leaves. The determination principle includes ultrasonic extraction of defoliant in samples with acetonitrile and water mixed solvent, and quantitative determination by HPLC-MS/MS analysis technology.