Miniaturized setup for fluorescence sensing with optodes: Characterization of a new hemicyanine ion-selective-based membrane

A miniaturized and robust optical fluorosensor, designed as a portable instrumentation for the in situ analysis of ions in water samples by using optodes has been constructed with low cost discrete optical components. The chemical recognition element of the device consists of a plasticized PVC-based fluorescent optode, which includes a new hexamethine–hemicyanine dye as a fluorophore. The signal can be attributed to a certain analyte depending on the ionophore employed. In this work, a commercial potassium ionophore (valinomycin) has been used to formulate a model membrane selective to potassium. The sensor has been fully characterized using a simple flow injection analysis (FIA) system and analytical parameters such as sensitivity (0.71 mV dec−1), limit of detection (2.2 × 10−5 M K+), repeatability (R.S.D. = 4.2%), reproducibility, lifetime and ionic interferences have been determined. The developed miniaturized system has been applied to the potassium concentration determination in spiked tap water samples. The obtained results have been compared to those acquired by the ICP-OES reference method and the suitability of the experimental setup for the determination of ions in water samples by the miniaturized fluorescence proposal has been demonstrated.