L-Thiazolidine-4-carboxylic acid monolayer was prepared on gold electrodes through the self-assembly approach. Such novel thioether-based monolayer could efficiently preconcentrate Cu 2+ , which provided a simple, stable and reproducible method for the determination of Cu 2+ . The modified electrodes were stable enough to be continuously used for one week (more than 30 times regeneration) with lower than 10% decrease in the response. They retained their initial activity for more than one month if used once a day. The calibration curve was linear for Cu 2+ from 0.6 to 158.8 μg L −1 with a detection limit of 0.38 μg L −1 . The relative standard deviation was 3.2% for a series of six successive measurements. The proposed method was applied in the determination of Cu 2+ in mineral water and human hair samples.L-thiazolidine-4-carboxylic acid, copper ions, gold electrode, thioether monolayer