Smart Sensor Based on Multiple Cascaded Michelson Interferometers with a Long-Period Fiber Grating for Recognition of Paracetamol Concentrations in Solutions

This work introduces a refractometric sensor based on multiple cascaded Michelson interferometers fabricated with long-period fiber gratings to classify different commercial brands of paracetamol as well as to measure solutions with different paracetamol concentrations. The operating principle is based on the interaction of light with the fiber–medium interface, such that variations in the refractive index provoke changes in the spectrum profile that can be measured at the output of the device. The brands used were Medley, Mejoral 500, Tempra, Tylenol, and excipient-free paracetamol (EFP). A support vector machine (SVM) classifier was used to recognize each brand with an F1-score of 92%. Also, using a projection to latent structures regression (PLSR), it was possible to quantify the paracetamol concentration with the best limit of detection (LOD) of 1.58 g/kg for the Mejoral brand.