Lawrence K. Wang, Mu-Hao Sung Wang, Nazih K. Shammas, Valerie Renak and Yung-Tse Hung (2020). Cationic surfactant analysis with good laboratory practice. In: “Environmental Science, Technology, Engineering, Arts, and Mathematics (STEM)”, Lawrence K. Wang, Mu-Hao Sung Wang and Nazih K. Shammas (editors). Volume 2020, Number 4, April 2020; 42 pages. Lenox Institute Press, Newtonville, NY, 12128-0405, USA. No. STEM-VOL2020-NUM4-APR2020. ………….ABSTRACT: The objectives of this research are to: (a) demonstrate how to select an organic solvent (such as 1,1,1-trichloroethane) for spectrophotometric determination of cationic surfactant in water and wastewater, (b) investigate and recommend possible better organic solvents for surfactant analysis; and (c) introduce good laboratory practice for personal protection, laboratory protection and hazardous waste management. Specifically this research involves selection of alternate less toxic and greener organic solvent for use in a methyl orange method for colorimetric determination of cationic surfactants in the 0.2 to 2.0 mg/L range. The principles, steps and management of the methyl orange method include: (a) complexation of cationic surfactant with methyl orange at acidic pH condition forming a methyl orange-surfactant complex; (b) organic solvent extraction; (c) water-solvent phase separation; (d) spectrophotometric measurement and (e) good laboratory practice and laboratory hazardous waste management.