Voltammetry Determination of Pb(II), Cd(II), and Zn(II) at Bismuth Film Electrode Combined with 8-Hydroxyquinoline as a Complexing Agent

Table 1

Factors in BBD and their levels.

	Bismuth concentration (X1, ppb)	pH (X2)	Oxine concentration (X3, ppb)
Central level (0)	600	6	581
High level (+1)	1000	8	1016
Low level (–1)	200	4	145