Handout14-pH&Ion

Handout14-pH&Ion - CEM 834 pH and ION SELECTIVE...

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CEM 834 pH and ION SELECTIVE ELECTRODES FALL 2005 FIGURE 1: Schematic representation of a typical glass membrane electrode for pH measurement. TABLE I: Properties of cation-selective glass membranes. Ion Glass Composition Selectivity Coefficient Remarks Li + 15 25 60 Li 2 O Al 2 O 3 SiO 2 Na + 11 18 71 Na 2 O Al 2 O 3 SiO 2 3 K , Li Na , Li 10 K 3 . 0 K , - < + + + + 11 pH at 10 x 4 K 4 K , Na - + + 7 pH at 10 x 3 K 3 K , Na - + + Best for Li + in presence of H + and Na + Nernst type of response to ~10 –5 M Na + 10.4 22.6 67 Li 2 O Al 2 O 3 SiO 2 5 K , Na 10 K - + + Highly Na + selective, but very time-dependent K + 27 5 68 Na 2 O Al 2 O 3 SiO 2 05 . 0 K Na , K + + Nernst type of response to <10 –4 M K + Ag + 28.8 19.1 52.1 Na 2 O Al 2 O 3 SiO 2 5 H , Ag 10 K - + + Highly sensitive and selective to Ag + , but poor stability 11 18 71 Na 2 O Al 2 O 3 SiO 2 3 Na , Ag 10 K - < + + Less selective for Ag + but more reliable
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FIGURE 2: Schematic representation of a liquid ion-exchange membrane electrode. TABLE II:
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This note was uploaded on 07/25/2008 for the course CEM 834 taught by Professor Mcguffin during the Fall '05 term at Michigan State University.

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Handout14-pH&amp;amp;Ion - CEM 834 pH and ION SELECTIVE...

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