Bio-Rad Chelex® 100 Resin - Manual (Page 4)

Table 1. Selectivity for Divalent Cations
Hg +2 1060 Fe +2 0.130
Cu +2 126 Mn +2 0.024
UO +2 5.70 Ba +2 0.016
Ni +2 4.40 Ca +2 0.013
Pb +2 3.88 Sr +2 0.013
Zn +2 1.00 Mg +2 0.009
Co +2 0.615 Na +1 0.0000001
Cd +2 0.390
Actual selectivity values for any particular system
depend on the pH, ionic strength, and the presence of
other complex-forming species. Thus Hg
+2 appears
high in the selectivity series in the presence of nitrate
ions, but low in the series in the presence of chloride
ions, with which it forms a complex. The approximate
order of selectivity for cations in nitrate or chloride
solutions is:
Cu +2 >>Pb +2 >Fe +3 >Al +3 >Cr +3 >Ni +2 >Zn +2 >Ag +
>Co +2 >Cd +2 >Fe +2 >Mn +2 >Ba +2 >Ca +2 >>>Na +
A selectivity series for cations in an acetate buffer
system at pH 5 is:
Pd +2 >Cu +2 >>Fe +2 >Ni +2 >Pb +2 >Mn +2 >>
Ca +2 = Mg +2 >>> Na +
The selectivity for various cations in aqueous
solutions at pH 4 is:
Hg +2 >Cu +2 >Pb +2 >>>Ni +2 >Zn +2 >Cd +2 >Co +2 >Fe +2 >
Mn +2 >Ca +2 >>>Na +
The selectivity at pH 9 in the presence of 1.5 M
(NH
4
)
2
SO
4
is:
Co +2 >Ni +2 >Cd +2 >Cu +2 >Zn +2 >Ca +2 >>>Na +
4 5
LIT200B 6/17/98 11:49 AM Page 4