Fluorescent Hydrophobic Test Strips with Sterically Integrated Molecular Rotors for the Detection of Hydrocarbons in Water and Soil with an Embedded Optical Read-Out

Contamination of natural bodies of water or soil withoils andlubricants (or generally, hydrocarbon derivatives such as petrol,fuels, and others) is a commonly found phenomenon around the worlddue to the extensive production, transfer, and use of fossil fuels.In this work, we develop a simple system for the on-field detectionof total petroleum hydrocarbons (TPHs) in water and soil. The testis based on the measurement of the fluorescence signal emitted bythe molecular rotor 2-[ethyl[4-[2-(4-nitrophenyl)ethenyl]phenyl]amino]ethanol(4-DNS-OH). This dye is embedded in a hydrophobic polymericmatrix (polyvinylidene fluoride), avoiding interactions with waterand providing a robust support for use in a test strip fashion. Togetherwith the strips, an embedded optical system was designed for fluorescencesignal read-out, featuring a Bluetooth low-energy connection to acommercial tablet device for data processing and analysis. This systemworks for the detection and quantification of TPHs in water and soilthrough a simple extraction protocol using a cycloalkane solvent witha limit of detection of 6 ppm. Assays in surface and sea waters wereconclusive, proving the feasibility of the method for in-the-fieldoperation.