The effect of the hydronium concentration on the accumulation
process is investigated in the pH range 3–12 (ESM Fig. 2(a)). The
stripping peak current gradually increases up to pH 7 and remains
almost same till pH 10 thereafter it decreases. The lesser stripping
current at lower pH is attributed to the less effective complexation
reaction between mercury ions and the modifier due to protonation of
organic ligand/indicator molecule. Whereas, at higher pH values the
hydrolysis of mercury ions interferes with the accumulation which
leads to the saturation of modified interface, hence current response
remains same [15].