A hybrid method combining an electrochemical technique and fluorescence measurement for the highly selective and sensitive detection of Cd²⁺

We developed a hybrid method combining an electrochemical technique and fluorescence measurement to detect Cd²⁺ in water samples. The electrochemical deposition and stripping technique provided a clean and selective pretreatment for transferring and concentrating Cd²⁺ from original turbid samples to blank buffer, followed by fluorescence quantification. Cd²⁺ in the original samples was co-deposited with Bi³⁺, which could provide a fresh bismuth film and concentrate a higher amount of Cd²⁺ onto a portable screen-printed electrode. The water-soluble compound Fura-2 was introduced as the fluorescent indicator for Cd²⁺ quantification, with the purpose of eliminating the error caused by the transfer to buffer. The detection results using real samples exhibited an excellent anti-interference ability, and showed a good linear correlation (correlation coefficient of R = 0.993). Moreover, the system was highly sensitive as a detection limit of 1.0 nmol L^-1 could be achieved through a repeated electrochemical pretreatment process. This hybrid method is selective, sensitive, convenient and portable. It is promising for in field heavy metal ion determination in remote environments.