Fig. 7. (a) SWASV for simultaneous detection of Cd²⁺, Pb²⁺, Cu²⁺ and Hg²⁺ under optimized SWASV conditions (100 to 350 nM). (b) Interference study of PPy/MoS₂/GCE sensor with addition of equal concentrations (100 nM) of Pb²⁺, Cr³⁺, Fe²⁺, Fe³⁺, Ni²⁺, Co²⁺ and K⁺ for each trial. (c) SWASV reproducibility of the PPy/MoS₂/GCE sensor under self-storage conditions. (d) Stability of the PPy/MoS₂/GCE sensor for SWASV detection of 300 nM of Pb²⁺ in 0.1 M Na–Ac buffer solution, pH = 5.0, deposition potential = −0.9 V and deposition time = 9 min.