In the present study, a simple and inexpensive method has been presented for on-site determination of iodide ions in various aqueous samples. The proposed method is based on the fluorescence quenching process of rhodamine B and the use of a home-made portable fluorimete
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In the present study, a simple and inexpensive method has been presented for on-site determination of iodide ions in various aqueous samples. The proposed method is based on the fluorescence quenching process of rhodamine B and the use of a home-made portable fluorimeter. In the fluorimeter, light-emitting diodes with emission wavelength of 530 nm (as the excitation source) and a mobile phone (as the detector and data processing unit) have been used. Experiments showed that in the presence of iodide ions, the fluorescence intensity of rhodamine B decreases. The fluorescence intensity changes of rhodamine B was determined by taking digital images of rhodamine B solutions and analyzing these images. Digital image analysis showed when the fluorescence intensity of rhodamine B changes, the values of the G and R channels change, too. Therefore, the values of these two channels were used as analytical signals for determination of the concentration of iodide ions. After investigating experimental parameters affecting the quenching process of rhodamine B by iodide ions and selection of optimal conditions, based on ∆G as analytical signal, limit of detection was obtained 1.26 × 10⁻⁵ mol L⁻¹ and the calibration graph was linear in the range of 2.1 × 10⁻⁵ - 2.3 × 10⁻³ mol L⁻¹ with a correlation coefficient of 0.996. The relative standard deviation for 5 iodide solution with concentration of 1.57 × 10⁻⁵ mol L-1 was 0.83 %. The proposed method was successfully applied to determine iodide in water samples with satisfactory recovery ranged from 98.62% to 108.65%.
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