Miniature fluorescent sensor for chloride ion concentration determination based on modified Stern–Volmer Equation

•A novel sensor of detecting Cl− accurately from a very small amount of sample.•A modified Stern–Volmer Equation for using the miniature fluorescent sensor system.•The predictability of this modified Stern–Volmer Equation is verified.•The novel sensor based on modified equation is of great potential for CF diagnosis.

Sweat test based on chloride ion selective electrode is the common method for the diagnosis of Cystic Fibrosis (CF). In our previous study, the possibility of using chloride ion sensitive fluorescent dye to determine the chloride ion concentration with a small volume of sample has been explored. However, we found the conventional Stern–Volmer Equation is applicable only for large systems such as a fluorescent microscope with a large volume of sample and dye solution; and it is not valid for portable devices using a small photo detector and a small volume of sample and dye solution. Therefore, in this paper, extensive experiments were performed by using a miniature fluorescent detection system; the effects of the parameters including the concentration and the volume of fluorescent dye solution, the coefficient of Stern–Volmer plot, and the volume ratio of the fluorescent dye solution and the chloride solution were studied; and a modified Stern–Volmer Equation was obtained. Using the modified Stern–Volmer correlation, the miniature fluorescent detection device can detect the chloride ion concentration correctly and rapidly.