The voltammetric assay of Cu(II) was investigated using a carbon nanotube electrode (CNE) and fluorine immobilized onto a carbon nanotube electrode (FCNE) in cyclic voltammetry (CV), square-wave (SW) stripping voltammetry, and chronoamperometry. Optimum SW conditions were attained at working ranges of 0.01-0.11ngL(-1) Cu(II) (11 points), and a relative standard deviation of 1.68% (RSD, n=15) was observed at 10.0 microgL(-1) Cu(II). Within a 200s accumulation time, detection limit of 0.006 microgL(-1) was attained. The life span of each electrode was more than 1 month. The sensor was applied to tap water, blood, and rat tail vascular (in vivo). It was found that the sensor could be used with an interface system in the assay of live cells and non-treated blood.