Table 1.

Effect of possible interfering ions on the SPE preconcentrations of Co(II) and Hg(II).

Recoverya (%)
Interferences	Interferic ion to metal ion ratio	Co(II)	Hg(II)
Na(I)	8000	98 ± 0.4	99 ± 0.2
K(I)	8000	97 ± 0.6	99 ± 0.7
Ca(II)	200	98 ± 1.4	100.1 ± 0.9
Mg(II)	200	98 ± 0.8	99 ± 0.5
Zn(II)	20	97 ± 1.4	98 ± 0.8
Fe(II)	20	97 ± 1.0	98 ± 0.9
Cd(II)	10	98 ± 1.3	99 ± 1.1
Cu(II)	10	97 ± 1.4	98 ± 0.7
Ni(II)	10	96 ± 0.9	97 ± 1.4
Al(III)	10	97 ± 0.7	97 ± 1.3

^aConcentrations of the heavy metal ions are 10 µg L⁻¹.