Table 2.

Resulting matrix of the factorial design and analytical response*.

Run	Ca2+	Mg2+	Na+	K+	Cd2+	Fe2+	Cu2+	Integrated absorbance
1	0	0	0	0	0	0	0	0.2802
2	500	0	0	0	500	0	500	0.2471
3	0	500	0	0	500	500	0	0.0689
4	500	500	0	0	500	500	500	0.1440
5	0	0	500	0	0	500	500	0.1385
6	500	0	500	0	0	500	0	0.0709
7	0	500	500	0	500	0	500	0.0980
8	500	500	500	0	0	0	0	0.0821
9	0	0	0	500	500	500	500	0.0779
10	500	0	0	500	500	500	0	0.0120
11	0	500	0	500	0	0	500	0.0509
12	500	500	0	500	0	0	0	0.0137
13	0	0	500	500	0	0	0	0.0000
14	500	0	500	500	0	0	500	0.1234
15	0	500	500	500	500	500	0	0.0000
16	500	500	500	500	500	500	500	0.0286
17	250	250	250	250	250	250	250	0.0000

*Concentration of each interfering ion is given in μg L⁻¹.