A chemical profiling technique for sub-lethal acetolactate synthase (ALS)-inhibitor herbicides (e.g., sulfonylureas, imidazolines, triazolopyrimidine sulfonanilides, and pyrimidyloxy salicylic) was developed using 2-aminobutyric acid, and was found to be directly proportional to application rates in field studies on two varieties of potato plants. An uncomplicated, benign-by-design analytical method for the determination of 2-aminobutyric acid in plant tissue was developed. The method is simple, fast, and automated, entailing a water-trichloroacetic acid extraction followed by precolumn on-line derivatization using o-phthalaldehyde (OPA) solution and liquid chromatographic analyses. Use of reagents and chlorinated organic solvents, and generation of waste, are minimized as compared to other ALS-inhibitor herbicide analytical techniques. Recoveries for a series of fortified plant tissues ranged from 82 to 103%. Two 20-day field trials on two potato varieties, Russet Burbank and Shepody, were conducted during the 2000 and 2001 growing seasons. The study demonstrated that the 2-aminobutyric acid method is an excellent, selective chemical marker technique for ALS-inhibitor herbicides for real world plant matrixes.