Introduction to Soil Chemistry

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Table 5.1. Ion-Selective Electrodes and Their Characteristics
Electrode/Ion a Type Molar Range a Interferences a
Ammonia Gas sensing/combination 1.0–5 ¥ 10-7 Volatile amines, Hg +
Bromide Solid state 1.0–5 ¥ 10-5 S2- must not be present; CN- ,
I- ,NH3,Cl- ,HO- Cadmium Solid state/combination 10-1 –10-7 Pb2+ ,Hg2+ ,Cu2+ Calcium Half-cell 1.0–5 ¥ 10-7 Na + ,Pb2+ ,Fe2+ ,Cu2+ , H +
Carbon dioxide Gas sensing 3 ¥ 10-2 –10-5 Volatile organic acids
Lead Solid state/half-cell 0.1–10-6 Cu2+ ,Ag + ,Fe3+ ,Cd2+ ,Ag +
Nitrate Half-cell 1.0–7 ¥ 10-6 - - - - - ClO4,I, ClO3,CN,Br, - - 2- - -
NO2,HS,CO3, HCO3,Cl Nitrogen oxide Gas sensing/combination 5 ¥ 10-3 –3.6 ¥ 10-6 CO2, volatile weak acids
Oxygen Gas sensing/combination 0–20ppm —
Perchlorate Half-cell 1.0–7 ¥ 10-6 I- - - - - ,NO3, ClO3,NO2,CN, - - 2- -
NO2, HCO3,CO3,Cl Potassium Half-cell 1.0–10-6 Cs + ,Na + + + ,NH4 ,H
Redox/ORP Combination — —
Sodium Half-cell Saturated to 10-6 Ag + ,K + ,H + ,Li + ,Cs + ,Tl +
a This is not an exhaustive list of ISE electrodes or number of interferences. Also, manufacturers’ specifications must be consulted as different materials
and construction may result in different interferences and sensitivities.