Fabrication, characterisation and optimisation of novel salicylic acid sensors using different reagents and artificial neural network

Two optical fiber chemical sensors for salicylic acid (SA) have been fabricated using ferric(III) nitrate and copper(II) nitrate as reagent. Ion exchange resin, Dowex 50×8 had been used as solid support and optimisation was done by using artificial neural network (ANN). SA sensor using immobilised Fe(III) gave maximum reflectance at wavelength of 786 nm and pH 2.1. Dynamic range of SA concentration had been extended using ANN (15 hidden neurons) from 0.02 - 0.50 g/L to 0.02 - 2.00 g/L. SA sensor based on immobilised Cu(II) showed maximum reflectance at pH 6.5 and wavelength of 725 nm. ANN with 5 hidden neurons was able to extend dynamic range of SA concentration from 0.40 - 1.40 g/L to 0.05 - 2.00 g/L. Sum-squared error (SSE) for SA sensor based on Fe(III) and Cu(II) were 0.0140 g/L and 0.0310 g/L, respectively. These two sensors were stable for a period of more than 24 hours.