Construção de um fotômetro portátil com aquisição de dados via smartphone para determinação de oxalato em infusões

Abstract

Internet of Things (IoT) is a term that includes the set of electronic devices connected to the Internet and interconnected in order to positively impact different aspects of everyday life. Internet of Things (IoAT) is the term designated to the said set of electronic devices in the field of Analytical Chemistry. There are several studies in the literature about the creation of photometers using Light Emitting Diode (LED) as a source of radiation and a possibility of application of these devices in the determination of oxalate in tea samples. Tea is the most consumed flavored beverage in the world today and is rich in oxalate. This study consists in the creation of an IoT device for oxalate determination in tea samples using the SPADNS method. This method is based on the absorption difference of Zr(IV)-SPADNS and SPADNS compounds in the interval of 580-600 nm. The photometer construction was performed using an LED with maximum emission of 590 nm as a light source and the TSL2591 sensor was used as a light detector. The physical support for adjustment and accommodation of the components was printed on a 3D printer. A Bluetooth HC-05 module for remote data acquisition was added to the system. The developed procedure based on the formation and breakage of the SPADNS-Zr complex showed a linear range of 0.3 to 10 mg L-1 with coefficient R = 0.996, Limit of Detection (LOD) = 0.2 mg L-1 and Limit of Quantification (LOQ) = 0.7 mg L-1. Were analyzed 10 infusion samples acquired in local trade and the oxalate values obtained were between 21.4±0.8 and 141.7±0.6 mg L-1. The addition and recovery studies showed satisfactory results between 96.6 and 109.7%. The proposed procedure presents anaytical characteristcs comparable to other established methods in literature and the absence of previous sample treatment makes the device a great alternative for point-of-care analysis.