Effect of foreign metal ions on the determination of Co(ii) by the proposed method.

Foreign metal ion	Tolerance limit (mg L−1)
Cu(ii)	10.1
Fe(ii)	10.2
Zn(ii)	11.1
Ni(ii)	12.4
Cd(ii)	13.2
Mg(ii)	31.0
Mn(ii)	31.2
Al(iii)	32.0
Fe(iii)	34.1
Sn(ii)	35.2
Sb(iii)	35.4