Table 6.2 Characteristics of some ion selective electrodes
Ion to be
monitored
Type of elctrode Concentration range,
MOptimum pH Approximate values of selectivity
constants for interfering ions, k1,2Na+ glass 100 – 105 > 7 H+ 102
Cs+, Li+ 0.002
K+ 0.001
Br– solid-state 100 – 5 × 10 –^62 –^12 S^2 – , I–, CN– ~ 106
Cl– sold-state 106 – 5 × 10 –^52 –^11 I–, CN– ~ 109
S^2 – ~^106
Br– ~^105
F– solid-state single
crystal
100 – 106 5 –^8 OH– ~ 104Ca2+ PVC-gel 100 – 5 × 10 –^76 –^8 Zn2+ 3.2
Pb2+ 0.063
Mg2+ 0.014
PVC-gel^100 –^7 ×^10 –^63 –^10 ~ 10^6I–^20
Br– 0.1
0.04
Cl– 0.004
CO 2 gas-sensing 10 –^2 – 10 –^4 — volatile, weak acids
interfere
NH 3 gas-sensing 100 – 10 –^6 — volatile amines
interfere
Figure 6.2
Glass electrode.