Pulse techniques in electron paramagnetic resonance (EPR) allow for a reduction in measurement times and increase in sensitivity but require the synthesis of paramagnetic probes with long relaxation times. Here it is shown that the recently synthesized phosphonated trityl radical possesses long relaxation times that are sensitive to probe the microenvironment, such as oxygenation and acidity of an aqueous solution. In principle, application of Fourier transform EPR (FT‐EPR) spectroscopy makes it possible to acquire the entire EPR spectrum of the trityl probe and assess these microenvironmental parameters within a few microseconds. The performed analysis of the FT‐EPR spectra takes into consideration oxygen‐, proton‐, buffer‐, and concentration‐induced contributions to the spectral shape, therefore enabling quantitative and discriminative assessment of pH, pO2, and concentrations of the probe and inorganic phosphate.

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This work presents the fabrication of Nafion (Nf) or Nafion/Multiwalled Carbon Nanotubes (Nf/MWCNTs) modified gold microarray (Au‐µA) and macro‐(Au‐M)electrode biosensors. The surface morphologies of the above electrodes were examined using SEM. The catalytic properties of the above electrodes towards dopamine were tested using square wave voltammetric technique. The Nf/MWCNT/Au‐µA electrode exhibited a wide range (0.1–1000 nM) of linearity among the other electrodes. The LOD of Nf/MWCNT/Au‐µA electrode was 50 pM for dopamine in the presence of 5000 µM ascorbic acid. Therefore, the Nf/MWCNT/Au‐µA biosensor was applied for the determination of dopamine in human serum.