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Article

Optical Sensing of Nitrogen, Phosphorus and Potassium: A Spectrophotometrical Approach toward Smart Nutrient Deployment

1
Centre for Applied Photonics, INESC TEC, Faculty of Sciences of the University of Porto, Rua do Campo Alegre, s/n, 4169-007 Porto, Portugal
2
Physics and Astronomy Department, Faculty of Sciences of the University of Porto, Rua do Campo Alegre, s/n, 4169-007 Porto, Portugal
*
Authors to whom correspondence should be addressed.
Chemosensors 2019, 7(4), 51; https://doi.org/10.3390/chemosensors7040051
Received: 2 August 2019 / Revised: 8 October 2019 / Accepted: 22 October 2019 / Published: 29 October 2019
(This article belongs to the Special Issue Optical Chemosensors and Biosensors)
The feasibility of a compact, modular sensing system able to quantify the presence of nitrogen, phosphorus and potassium (NPK) in nutrient-containing fertilizer water was investigated. Direct UV-Vis spectroscopy combined with optical fibers were employed to design modular compact sensing systems able to record absorption spectra of nutrient solutions resulting from local producer samples. N, P, and K spectral interference was studied by mixtures of commercial fertilizer solutions to simulate real conditions in hydroponic productions. This study demonstrates that the use of bands for the quantification of nitrogen with linear or logarithmic regression models does not produce analytical grade calibrations. Furthermore, multivariate regression models, i.e., Partial Least Squares (PLS), which consider specimens interference, perform poorly for low absorbance nutrients. The high interference present in the spectra has proven to be solved by an innovative self-learning artificial intelligence algorithm that is able to find interference modes among a spectral database to produce consistent predictions. By correctly modeling the existing interferences, analytical grade quantification of N, P, and K has proven feasible. The results of this work open the possibility of real-time NPK monitoring in Micro-Irrigation Systems. View Full-Text
Keywords: nitrogen; phosphorus; potassium; nutrient; spectrophotometry; optical sensor; artificial intelligence; optical fiber nitrogen; phosphorus; potassium; nutrient; spectrophotometry; optical sensor; artificial intelligence; optical fiber
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MDPI and ACS Style

Monteiro-Silva, F.; Jorge, P.A.S.; Martins, R.C. Optical Sensing of Nitrogen, Phosphorus and Potassium: A Spectrophotometrical Approach toward Smart Nutrient Deployment. Chemosensors 2019, 7, 51. https://doi.org/10.3390/chemosensors7040051

AMA Style

Monteiro-Silva F, Jorge PAS, Martins RC. Optical Sensing of Nitrogen, Phosphorus and Potassium: A Spectrophotometrical Approach toward Smart Nutrient Deployment. Chemosensors. 2019; 7(4):51. https://doi.org/10.3390/chemosensors7040051

Chicago/Turabian Style

Monteiro-Silva, Filipe; Jorge, Pedro A.S.; Martins, Rui C. 2019. "Optical Sensing of Nitrogen, Phosphorus and Potassium: A Spectrophotometrical Approach toward Smart Nutrient Deployment" Chemosensors 7, no. 4: 51. https://doi.org/10.3390/chemosensors7040051

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