Biomedical Engineering Reference
In-Depth Information
cobalt [32], manganese [33], and palladium [21] hexacyanoferrates on aluminum have
been reported.
13.3 AMPEROMETRIC SENSORS FOR REDOX-INACTIVE
CATIONS AND ELECTROACTIVE COMPOUNDS
13.3.1 Sensors for redox-inactive cations
Redox-inactive cations attract a particular interest for analytical chemists because of
their importance in environmental control, industry, and medicine. For instance, in
clinical diagnostics, tests for blood electrolytes (Na
, K
) are routine, because devia-
tion of cation content from their normal values indicates a number of pathologies.
The participation of cations in redox reactions of metal hexacyanoferrates provides a
unique opportunity for the development of chemical sensors for non-electroactive ions.
The development of sensors for thallium (Tl
) [15], cesium (Cs
) [34], and potassium
(K
) [35, 36] pioneered analytical applications of metal hexacyanoferrates (Table 13.1).
Later, a number of cationic analytes were enlarged, including ammonium (NH
4
) [37],
rubidium (Rb
) [38], and even other mono- and divalent cations [39]. In most cases
the electrochemical techniques used were potentiometry and amperometry either under
constant potential or in cyclic voltammetric regime. More recently, sensors for silver
[29] and arsenite [40] on the basis of transition metal hexacyanoferrates were proposed.
An apparent list of sensors for non-electroactive ions is presented in Table 13.1.
Some monovalent ions promote the electroactivity of metal hexacyanoferrates
rather similarly, which affects selectivity of the corresponding sensors. In particular, it
TABLE 13.1
Sensors for redox inactive cations
Analyte
Me-hexacyanoferate, Me:
Ref.
Cs
Cu
[34, 47]
K
Cu, Ag
I
[Mo(CN)
8
]
4
, Fe, Co, Ni, Zn
[36, 48], [35], [49-51], [41],
[42], [24]
NH
4
Cu
[52]
Tl
Cu, Fe
[15, 53], [54, 55]
Ag
Ag
[29]
As
3
Fe
[40]
K
, Cs
Fe, Cu, Ag, Ni, Cd
[56]
K
, NH
4
Cu
[37]
K
, Rb
, Cs
, NH
4
Cu, Ni, Fe
[38], [57, 58]
Cs
, K
, Na
, Li
Ni
[59]
Li
, Na
, K
, Rb
, Cs
, H
, Tl
Tl
[30]
Mono- and divalent cations
Cu, Ni
[39]
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