A cost-effective microfluidic device for determination of biodiesel content in diesel blends Soares, Samara Ramos Lorente, Celia Esperanza Rocha, Fabio R.P. Erenas Rodríguez, Miguel María Orbe Payá, Ignacio De López Ruiz, Nuria Capitán Vallvey, Luis Fermín Microfluidics Digital image colorimetry Quality control Alkyl esters content Renewable fuel Diesel blends The increasing production and extensive use of biodiesel in the latest years call for the development of fast and cost-effective procedures for point-of-care analysis. One of the main quality parameters is the biodiesel content in diesel blends, which needs to conform to regional legislations. In this work, a microfluidic device exploiting chemical derivatization of alkyl esters and detection by smartphone-based digital-image colorimetry was developed. It was designed to ensure proper experimental conditions for chemical derivatization, including re- agent release, and photometric measurements. Analytes reacted with alkaline hydroxylamine yielding the cor- responding alkyl hydroxamates, measured as colored Fe(III) complexes. Analytical response was based on the measurement of the G (green) channel from RGB color system. By taking methyl linoleate as a model compound, a linear response was obtained from 0.1% to 0.6%(v/v) (Analytical signal = 69.6 +2.1 C, r = 0.999), coefficient of variation (n = 10) of 4.0% and limit of detection (99.7% confidence) of 0.04%(v/v). Procedure consumes 1.2 µL of sample, 230 µg of hydroxylamine, 480 µg of NaOH, 14 µg of Fe(III) and equivalent to 1.2 µL of 69%(v/v) HNO3. Accurate results were achieved in relation to the MIR reference method, with agreement at the 95% confidence level 2023-06-12T09:11:58Z 2023-06-12T09:11:58Z 2023-05-27 journal article Sensors & Actuators: B. Chemical 390 (2023) 134033 https://hdl.handle.net/10481/82334 10.1016/j.snb.2023.134033 eng http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional