The ubiquity and importance of anions in many crucial roles accounts for the current high interest in the design and preparation of effective sensors for these species. Therefore, a tilted fiber Bragg grating sensor was fabricated to investigate individual detection of different anion concentrations in ethyl acetate, namely acetate, fluoride and chloride. The influence of the refractive index on the transmission spectrum of a tilted fiber Bragg grating was determined by developing a new demodulation method. This is based on the calculation of the standard deviation between the cladding modes of the transmission spectrum and its smoothing function. The standard deviation method was used to monitor concentrations of different anions. (...)

Agradecimentos: This research was partially funded by the São Paulo Research Foundation (FAPESP) (#2014/50632-6). J.H.O. gives thanks to CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico) for financial support