similar to the mercury electrode and it is more environmentally
friendly [14]. The bismuth (Bi) can be constructed by electrodeposition
on substrates including glassy carbon [15], screen-printed
carbon ink (SPCE) [16]. Carbon nanotubes (CNTs) have been proven
to possess potential for heavy metals analysis due to their high
electrical conductivity, high surface area, significant mechanical
strength, and good chemical stability. Therefore, the fabrication of
screen-printed carbon nanotubes electrode (SPCNTE) is attractive.
In effort to improve the sensitivity of heavy metals by electrochemical
analysis, Bi-SPCNTE was used as the working electrode [17,18]
in batch analysis.