Doping of PDMS-NQS Sensors to Modify Their Response and Sustainability: Ammonia Quantitation in Farm Atmospheres as a Case Study.

In this work, different passive solid composites of 1,2-naphthoquinone-4-sulfonic acid sodium salt (NQS) embedded in polydimethylsiloxane (PDMS) and tetraorthoethylsilicate (TEOS) doped with silica nanoparticles (SiO₂NPs) were obtained. New composites including deep eutectic solvent (DES) and choline chloride (ChCl) were synthetized and compared here vs. ionic liquid (IL) which was previously proposed, from their passive response with time. Monitoring and controlling of ammonia levels inside poultry and rabbit farming facilities are essential for animal welfare, workers' exposure assessment, and measurement of environmental emissions. Real poultry and rabbit farm atmosphere samples were analyzed at different sensor exposition times, obtaining results between two and eight ppmv of NH₃ in all cases. The results were compared by air sampling with Tedlar bags and analysis by UHPLC-QTOF from a miniaturized SPE supported derivatization that was developed. As primary amine group NH₃ was the major component in the farm atmosphere, the presence of methylamine was negligible. PDMS-based sensors with DES or ChCl add new potential for previously developed composites, improving the versatility for controlling ammonia by using new sustainable composites with different time responses.