A single-droplet-based electrochemical fluorescence method for the determination of aluminum at the nanomolar level

This paper combines a single-droplet-based electrochemical system with an optical fiber fluorescence spectrometer to develop an electrochemical fluorescence method for determining the nanomolar level of aluminum. Al3+ ions were preconcentrated on a glassy carbon rotating disk electrode (RDE) at -2.0 V. After preconcentration, the RDE was rinsed and a droplet (80 mu L) of solution containing 0.2 mM 8-hydroxyquinoline-5-sulfonic acid (HQS) was sandwiched between the RDE (above) and the reference/counter integrated electrode (below). Subsequently, the RDE was rotated and aluminum was stripped into the droplet at -1.4 V; the fluorescence intensity was then measured using a 395 nm LED excitation source. The fluorescence intensity at 515 nm is positively correlated with Al3+ concentration, allowing the determination of aluminum. This method exhibits high selectivity and sensitivity with a detection limit of 7.6 nM. Trace aluminum in real samples was determined by this method and satisfactory results were obtained.