Simultaneous Determination of Zn(II), Cd(II), Pb(II), and Cu(II) Using Differential Pulse Anodic Stripping Voltammetry at a Bismuth Film-Modified Electrode

Table 2

Design matrix and responses for full factorial design.

Run	Coded variable levels				Anodic peak current, Ipa (µA)
	x1	x2	x3	x4	Cu	Pb	Cd	Zn
1	0	–1	0	–1	2.291	2.294	1.332	0.918
2	+1	0	–1	0	2.053	2.079	1.233	0.789
3	–1	–1	0	0	2.543	2.531	1.510	1.104
4	0	–1	–1	0	2.297	2.305	1.336	0.909
5	+1	0	+1	0	2.513	2.596	1.531	1.101
6	0	0	–1	–1	2.254	2.317	1.401	0.980
7	–1	0	–1	0	2.524	2.612	1.483	1.076
8	0	0	–1	+1	2.532	2.562	1.488	1.059
9	+1	0	0	–1	1.991	2.066	1.181	0.788
10	0	+1	–1	0	2.554	2.560	1.577	1.090
11	+1	–1	0	0	1.988	1.999	1.241	0.770
12	+1	+1	0	0	2.250	2.307	1.326	0.959
13	0	0	0	0	3.302	3.359	2.022	1.532
14	–1	+1	0	0	2.773	2.806	1.719	1.185
15	–1	0	0	+1	2.831	2.804	1.699	1.189
16	0	–1	0	+1	2.509	2.451	1.533	1.073
17	0	+1	0	–1	2.516	2.556	1.567	1.105
18	+1	0	0	+1	2.259	2.312	1.377	0.966
19	0	+1	+1	0	3.077	3.101	1.863	1.357
20	0	–1	+1	0	2.766	2.781	1.748	1.226
21	0	0	+1	–1	2.811	2.862	1.624	1.230
22	0	0	0	0	3.358	3.332	2.022	1.537
23	–1	0	0	–1	2.554	2.587	1.485	1.099
24	0	0	+1	+1	3.082	3.057	1.893	1.407
25	0	+1	0	+1	2.783	2.775	1.667	1.179
26	–1	0	+1	0	3.046	3.064	1.871	1.356
27	0	0	0	0	3.342	3.338	2.032	1.530