Table 2.

Tolerance limit of the foreign ions.

Foreign ions	Interference/Pb(II) ratio	Recovery (%)
H2PO4 −, HPO4 2−	7000	95
Na+, K+	5000	95
Ca2+, Mg2+	3000	105
Co2+	800	95
Cu2+, Mn2+	1000	105
Fe2+, Fe3+	400	95
Ni2+, Zn2+	1000	105
Al3+	100	95
Cr3+	800	95
Sn2+, Cd2+	600	105
Ag+	200	95
Sb3+, Cd2+	500	96

Conditions were the same as Figure 1.