Inexpensive Bismuth-Film Electrode Supported on Pencil-Lead Graphite for Determination of Pb(II) and Cd(II) Ions by Anodic Stripping Voltammetry

Table 1

Factors and respective lower and superior levels values.

Factors	Lower level (-)	Superior level (+)
Bi(III) concentration (mg L^−1)	150	250
Deposition potential (V)	-1.50	-1.10
Deposition time (s)	100	250