Fluorimetric Flow-Through Sensing of Quinine and Quinidine

We describe a single continuous-flow method for the determination of Quinine (QN) and Quinidine (QD) based on the enhancement of their native fluorescence by on-line transitory retention on a solid support placed in a flow cell. KCl solution was used as carrier/self-eluting solution. The active solid surface is regenerated by the carrier itself which also acts as eluting solution, thus making the microsensing zone reusable for subsequent measurements.In the range of 40 to 1260µL, the response of the sensor (_exc/_em=250/450nm) was directly proportional to the sample volume injected. The sensor was calibrated for three injection volumes: 40, 600 and 1000µL, responding linearly in the range of 40–800, 2–40 and 0.4–20µgL^–1 of QN and 20–600, 5–40 and 0.9–20µgL^–1 of QD with detection limits of 2.2, 0.2 and 0.1µgL^–1 (QN) and 3.9, 0.4 and 0.2µgL^–1 (QD), respectively. The relative standard deviation for ten independent determinations is 1.0% (QN) and 3.9% (QD). The sampling frequency ranges between 40 and 22h^–1 depending on the sample volume injected. This sensor was satisfactorily applied to the determination of QN in soft drink samples and a shampoo, and to the determination of QD in pharmaceutical preparations with equally satisfactory results.