Cost-effective smartphone-based method for low range chemical oxygen demand analysis
Inalmar D. Barbosa Segundo,
Jussara C. Cardozo,
Pollyana Souza Castro,
Amanda D. Gondim,
Elisama V. dos Santos,
Carlos A. Martínez-Huitle
Affiliations
Inalmar D. Barbosa Segundo
Renewable Energies and Environmental Sustainability Research Group, Institute of Chemistry, Federal University of Rio Grande do Norte, Campus Universitário, Av. Salgado Filho 3000, Lagoa Nova, Natal, RN CEP 59078-970, Brazil
Jussara C. Cardozo
Renewable Energies and Environmental Sustainability Research Group, Institute of Chemistry, Federal University of Rio Grande do Norte, Campus Universitário, Av. Salgado Filho 3000, Lagoa Nova, Natal, RN CEP 59078-970, Brazil
Pollyana Souza Castro
Institute of Chemistry, Federal University of Rio Grande do Norte, Av. Salgado Filho 3000, Lagoa Nova, Natal, RN CEP 59078-970, Brazil
Amanda D. Gondim
Renewable Energies and Environmental Sustainability Research Group, Institute of Chemistry, Federal University of Rio Grande do Norte, Campus Universitário, Av. Salgado Filho 3000, Lagoa Nova, Natal, RN CEP 59078-970, Brazil; Institute of Chemistry, Federal University of Rio Grande do Norte, Av. Salgado Filho 3000, Lagoa Nova, Natal, RN CEP 59078-970, Brazil
Elisama V. dos Santos
Renewable Energies and Environmental Sustainability Research Group, Institute of Chemistry, Federal University of Rio Grande do Norte, Campus Universitário, Av. Salgado Filho 3000, Lagoa Nova, Natal, RN CEP 59078-970, Brazil; National Institute for Alternative Technologies of Detection, Toxicological Evaluation and Removal of Mi-cropollutants and Radioactives (INCT–DATREM), Institute of Chemistry, UNESP, P.O. Box 355, Araraquara, SP 14800-900, Brazil
Carlos A. Martínez-Huitle
Renewable Energies and Environmental Sustainability Research Group, Institute of Chemistry, Federal University of Rio Grande do Norte, Campus Universitário, Av. Salgado Filho 3000, Lagoa Nova, Natal, RN CEP 59078-970, Brazil; Institute of Chemistry, Federal University of Rio Grande do Norte, Av. Salgado Filho 3000, Lagoa Nova, Natal, RN CEP 59078-970, Brazil; National Institute for Alternative Technologies of Detection, Toxicological Evaluation and Removal of Mi-cropollutants and Radioactives (INCT–DATREM), Institute of Chemistry, UNESP, P.O. Box 355, Araraquara, SP 14800-900, Brazil; Corresponding author at: Renewable Energies and Environmental Sustainability Research Group, Institute of Chemistry, Federal University of Rio Grande do Norte, Campus Universitário, Av. Salgado Filho 3000, Lagoa Nova, Natal, RN CEP 59078-970, Brazil.
Aiming the decentralization of monitoring policies and to facilitate the work of researchers, mainly in developing countries, the present method deals with the explanation of a simple and rapid protocol for chemical oxygen demand (COD) analysis through the use of digital smartphone devices coupled with a camera and a free app available for Android operating system that recognizes HSV (hue, saturation, value). The calibration of the method is done based on the theoretical values of potassium hydrogen phthalate for a proper and reliable build of the calibration curve by using the smartphone-based technique and the digested samples of COD. The coefficient of determination (R2) attained a value upper than 0.99, providing a high confidence levels, and the method achieved 97% of average accuracy in samples with COD values ranging from 0 to 150 mg L−1. Finally, the procedure here presented can be a great support for scientific laboratories and monitoring policies, once it can efficiently substitute expensive spectrophotometers and can improve and ensure the sustainable management of water sanitation, which is one of the sustainable goals proposed by the United Nations. • COD measurements, based on the use of a simple smartphone with a camera, can be a promising way for environmental analysis when spectrophotometers are not available, such as decentralized approaches. • The use of smartphone protocol is a novel initiative to fulfill sustainable development goal 6 on clean water and sanitation. • The smartphone is capable to read the difference of HSV values efficiently and can substitute the use of expensive spectrophotometers.
