Aguiar, Juliana I. S.Ribeiro, Susana O.Leite, AndreiaRangel, MariaRangel, António O. S. S.Mesquita, Raquel B. R.2023-03-082023-03-082023-02-012227-9040http://hdl.handle.net/10400.14/40497This work describes the development of an iron sensor based on a microfluidic paper-based technique, to attain iron quantification in natural waters. A new water-soluble naphthalene-3-hydroxy-4-pyridione ligand was used as a colour reagent, as it formed an orange complex with iron. As a newly described ligand, several chemical and physical parameters, namely, the sample and reagent volumes and reagent concentrations, were studied related to the formation of the coloured complex. The microfluidic paper-based analytical device (μPAD) assembly, namely, the use of different types of filter paper and different numbers of layers, was developed to obtain the best performance. Under the optimal conditions, a linear correlation was obtained in the range of 0.25–2.00 mg/L of iron, with a minimum detectable value of 0.07 mg/L. The proposed μPAD method was validated by an analysis of the certified samples and by a comparison of the tested water samples with the inductively coupled plasma (ICP) results (RE < 10%). Then, the μPAD device was successfully applied to the determination of iron in tap water, well water, river water, and seawater, with no need for any prior sample pre-treatment; recovery studies were also performed (average = 100.3% with RSD = 4.2%).eng3-hydroxy-4-pyridinone ligandIn situ analysisIron quantification sensorMicrofluidic paper-based analytical deviceNatural watersjournal article10.3390/chemosensors1102010185148909018000938899100001