GB/T 37363.1-2019 "Determination of Biocides in Coatings - Part 1: Determination of Isothiazolinone Content" is applicable to the detection of isothiazolinone-based biocides in coatings and related products. The sample is treated with a suitable extraction solvent, and after separation and purification, it is analyzed using appropriate analytical instruments (such as a high-performance liquid chromatograph). The method employs retention time for qualitative analysis and an external standard method for quantitative analysis. It specifies the sample pretreatment process, chromatographic conditions, and result calculation requirements, providing a standardized approach for controlling the content of such biocides in coatings and ensuring the accuracy and comparability of test results.