A novel chitosan-based resin functionalized with threonine moiety was synthesized, and applied to the collection/concentration of Mo, V, and Cu in environmental water samples, followed by their determination using inductively coupled plasma-atomic emission spectrometer (ICP-AES). The synthesized resin, crosslinked chitosan-threonine (CCTS-Thr), showed good adsorption behavior toward trace amounts of Mo, V, and Cu in a wide pH range.The adsorbed elements can be easily eluted using 2 mol L -1 of nitric acid, and their recoveries were found to be 90-100%. The CCTS-Thr was packed in a mini-column, which was then installed in a computer-controlled auto-pretreatment system (Auto-Pret System) for on-line trace-elements collection and determination by ICP-AES. Experimental parameters related to the improvement of sensitivity and reproducibility were optimized. The limits of detection (LODs) for target metals were found to be in sub-ppb level. The proposed method with L. Hakim et al. CCTS-Thr resin was successfully applied to the determination of Mo, V, and Cu in environmental water samples. The recovery test showed that common matrices which exist in environmental water samples did not interfere with the determination.