10,12-Pentacosadiynoic Acid Ethyl-d5 Ester is the labeled analogue of 10,12-Pentacosadiynoic Acid Ethyl Ester (P267990), the ethyl ester analogue of 10,12-Pentacosadiynoic Acid (P267985), which is used in the preparation of colorimetric and fluorescence sensors for cationic surfactants.