H+-selective microelectrodes with optimized measuring range for corrosion studies

• Two newly synthesized amines with tailored basicity were tested as H+-ionophores.
• Nitrophenyl octyl ether as membrane solvent provides the best H+-SE working range.
• Benzyldioctadecylamine-based H+-SE responses linear at pH 2.6–12.3 in 0.05 M NaCl.
• New H+-microelectrode was applied for pH scanning over corroding steel.

Two newly synthesized H+-selective ionophores: 2,3,4-tris(dodecyloxy)benzyldihexylamine and benzyldioctadecylamine, and six nitro-group containing solvents (2-nitrophenyl octyl ether, 2-nitrophenyl pentyl ether, 2-nitrophenyl phenyl ether, 1,2-dimethyl-3-nitrobenzene, 2-fluorophenyl 2-nitrophenyl ether, benzyl 2-nitrophenyl ether) were investigated to develop a membrane for glass-capillary H+-selective microelectrode with optimized measuring range for corrosion studies. It was shown that the microelectrode based on benzyldioctadecylamine and potassium tetrakis(4-chlorophenyl) borate as anionic site dissolved in 2-nitrophenyl octyl ether possessed the best working pH range (2.6–12.3), Nernstian slope (55.0 mV decade−1) and good time-related characteristics (potential drift 0.06 mV h−1, potential reproducibility ±0.1 mV and response time). It was successfully applied for pH measurements over corroding cut-edge samples of metallic coated steel using scanning ion-selective electrode technique.