Biomedical Engineering Reference
In-Depth Information
TABLE 4.1
Concentration range of the most important ions in blood and compositions of the corre-
sponding polymeric membrane sensors and their selectivities
Concentration
Selectivity, log
K
pot
IJ
Ion I
range, mM
Membrane composition
Na
10.4 K
:
H
pH:
Tri-
n
-dodecylamine, KTpClPB, PVC/DOS
9.8 Ca
2
:
11.1
7.35-7.45
Li
0.5-1.5
a
7-tetradecyl-2,6,9,13-tetraoxatricyclo[12.4.4.0
1.14
]
Na
:
3.1 K
:
3.6 Ca
2
:
5.0
docosane, KTpClPB, PVC/DBPA
Na
Li
:
2.8 K
:
136-145
Calix[4]arenecrown-4 ionophore, KTpClPB,
5.0 Mg
2
:
PVC/NPOE
4.5 Ca
2
:
4.4
K
Na
:
4.5 Mg
2
:
3.5-5.0
Valinomycin, NaTFPB, PVC/DOS
7.5 Ca
2
:
6.9
Ca
2
2.2-2.6
N,N,N
,N
-tetracyclohexyl-3-oxapentanediamide
Na
:
8.3 K
:
(ETH 129), KTpClPB, PVC/NPOE
10.1 Mg
2
:
9.3
Mg
2
Li
:
3.7 Na
:
3.2 K
:
0.8-1.3
Tetraamide ionophore, KTpClPB, PVC/NPOE
1.4 Ca
2
:
2.5
Cl
2,7-di-
tert
-butyl-9,9-dimethyl-4,5-xanthenediamine, Sal
:
1.8 NO
3
:
98-106
0.7 HCO
3
:
2.6
TDDMACl, PVC/NPOE
CO
2
35-40
b
Cl
:
6.0 Sal
:
0.8
Tweezer-type carbonate ionophore, TDMACl,
NO
3
:
3.4
PVC/DOA
Cl
:
2.5 NO
3
:
1.7
Phosphates 0.7-1.4
Uranyl salophene, PVC/NPOE
1-2
c
Cl
:
4.8 OAc
:
3.4
Salicylate
Sn(II) phthalocyanine
a
For patients under treatment with lithium salts.
b
Total carbon dioxide concentration.
c
For patients under treatment with aspirin.
clinical chemistry and ion-selective electrodes are implemented in all commercially
available clinical analyzers, large and small (Fig. 4.2). As the blood electrolyte activity
usually varies in a narrow range, a 10-100 microvolt precision of the potential meas-
urements is required, which is achieved by temperature-controlled fl ow-through cells
and frequent automated recalibrations. The use of disposable probes or cartridges with
precalibrated sensors is another option, simplifying analysis for an end-user.
Pharmaceutical analysis is another important area for ISEs [19]. A large number
of drugs were reported to be detectable by ISEs in pharmaceutical formulations and
during manufacturing processes. The concentration of drugs and their metabolites can
be measured in real biological fl uids. Although ISEs are currently not widely used in
pharmaceutical chemistry, they have a great potential and a number of ISE applications
have been developed in the last years [20]. Most drug-selective electrodes are based on
ion exchangers and exploit commonly high lipophilicities of drugs and metabolites.
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