Dye concentration determination with cross-sensitivity compensation

Cross sensitivity due to temperature variation and the presence of other contaminants in an analyte could affect the accuracy of concentration measurement made by a sensor. In this study, a miniaturized non-adiabatic interferometer fiber optic sensor (NAIFOS) is used to monitor the Remazol Black B (RBB) dye concentration in the presence of other contaminants, pH adjustment and temperature variation. The objective of this experiment is to investigate the ability and accuracy of the sensor to monitor RBB concentration under the influence of cross-sensitivity from a single spectrum, which is considered as an advantage over traditional sensing techniques. The developed sensor shows a dye concentration sensitivity of 0.0013 nm/ppm between 0 and 800 ppm when conducted room temperature without the presence of other contaminants. The influence of pH, suspended solids in the sample and temperature variation on the accuracy of the measurement is also examined. The results show that the sensor could still provide an accurate measurement if the pH value falls between 3.07 and 10.09 with very low concentration of suspended solids (approximately 1 mg/L). In addition, a corrective measure for temperature bias is carried out by compensating the cross-sensitivity effect and a model for temperature compensation is established. To the best of our knowledge, this might well be the first attempt to establish temperature correction and compensation for optical fiber sensing using non-adiabatic tapered fiber sensor. In extended experiments involving many concentration levels, the results obtained are encouraging.