Ratiometric Methods For Optical Fiber Instrumentation Based On Luminescence Sensors

The optical fiber instruments in analytical applications are usually based on a luminescence chemical sensor. Direct intensity measurements of the luminescence emission are, due to their simplicity, a very common measuring principle. Consequently, many optical fiber devices are based on the intensity measurement of the luminescence emission. Unfortunately, direct luminescent intensity measurements suffer from a series of non-analyte fluctuations, which make them inappropriate for the development of precise instrumentation. An alternative for solvents this trouble is to measure the lifetime of luminescence emission. In that case the drawback is an increase in the complexity of the measurement. A ratiometric measurement can solve many of the trouble previously exposed. When the excitation light interacts with a luminescence chemical sensor different optical emissions take place. Some of these emissions are analyte dependent and they are employed to extract the quantitative information required. The rest of emissions are usually considered like noise that can reduce the accuracy. With a ratiometric scheme this noise, or background light, is converted in a useful signal that can improve the accuracy of the measurement. In this paper we proposed two new ratiometric methods specially designed to be implemented with optical fiber instrumentation. The potential of our proposed ratiometric methods to overcome such problems of accuracy in luminescent sensing will be evaluated. The correct election of the methodologies with respect to the analytical performance of the chemical sensor will be also analyzed.