The spin-coating-based immobilization of ZnTPP-dyed cation exchange resin microbeads for reversible ammonia detection

Abstract

During the fabrication of a microfluidic chip for reversible ammonia detection, we applied a spin-coating-based method to immobilize cation exchange resin microbeads on which zinc tetraphenylporphyrin was dyed as an indicator material. The 4-layered microfluidic chip and a portable spectrometer constituted the core part of the integrated system. The results obtained for various wavelengths were compared, and the spectral intensity change at 450 nm was selected. The PDMS films at 2000–5000 rpm were investigated at ammonia concentrations ranging from 0.5 to 50 mg L⁻¹. The reversibility of zinc tetraphenylporphyrin was assessed by the results obtained after each cycle. After conducting the tests 75 times for various microfluidic chips, the stability of the method was confirmed with the maximal relative deviation being less than 10%. The introduced method exhibited significant potential for the detection of ammonia.