The analytical measurement of fluorescein, quinine and trace metal concentrations in solution using single bubble sonoluminescence

A single bubble was generated and levitated in a high-intensity sound field within a spherical flask excited in its fundamental mode. Under optimum experimental conditions the bubble was observed to emit light in the form of short flashes. This phenomenon is known as single bubble sonoluminescence (SBSL). Using this process, the emitted light from the bubble was monitored when solutions containing fluorescein, quinine and sodium, potassium and copper salts were placed in the cell. The results obtained indicated that reproducible signals related directly to the concentration of the species present in solution could be achieved using single bubble sonoluminescence. The results for the molecular species were compared with those obtained by fluorescence spectroscopy and, in the case of quinine, parallel determinations of concentration in a test solution were performed with consistent results. SBSL signals were also observed to exhibit a linear correlation with the concentration of several trace metal salts introduced to the solution in the measurement cell. However, it was not possible to demonstrate that the SBSL signals were derived from stimulated atomic emission or fluorescence, and it was concluded that the effect may result from an indirect effect involving the bubble excitation mechanism.