An IoT optical sensor for photometric determination of oxalate in infusions

Abstract

A new device exploiting an optical sensor and a remote-controlled IoT-Bluetooth acquisition board has been proposed for photometric measurements. A visible light-to-digital sensor (TSL2591) was connected to a microcontroller and the response signals were sent wirelessly over the Bluetooth connection. A LED was used as a light source for absorbance measurements. The point-of-care device was designed and fabricated using an FDM-based 3D printer with ABS thermoplastic filament, providing low-cost housing for the optoelectronics and the sample cell. To demonstrate the applicability effectiveness of our new device, an oxalate photometric smart sensor has been development. The quantification method exploited the reaction between oxalate and the red-colored complex Zr(IV)–SPADNS, leading to the decrease of color intensity associated with 590 nm. The analytical performance of the optical sensor obtained a linear range of 0.3–10 mg L−1, with limit of detection (LOD) and limit of quantification (LOQ) values of 0.2 mg L−1 and 0.7 mg L−1, respectively. The method was applied for the determination of oxalate in some infusions samples with satisfactory results and recoveries in the range of 96.6–109.7%. Miniaturized LED-based photometer approaches for oxalate determination presented an analytical performance similar to those obtained with the commercial spectrophotometer. However, the marriage of LED-based photometer with optical sensor enables the development of powerful IoT platforms for many important applications including food samples.