Chemistry Reference
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differences in the effective mobilities of the anions of interest, as the concentration of
nitrite, fluoride and phosphate in river water are usually too low to be detected in the first
stage.
Both the cross sectional area of the capillary tube and the concentration of the leading
constituent used in the second stage were optimised with
Table 14.2
Operational systems
Leading electrolytes
System No
.
Parameter
1st stage
2nd stage
Terminating electrolyte
Cl
−
Cl
−
CITR
b
1
Anion
Concentration (mmol L
−1
)
8
1
2
BALA
a
BALA
a
H
+
Counter ion
Co-counter ion
BTPc
-
-
Concentration (mmol L
−1
)
3
-
-
0.1%HEC
d
0.1%HEC
d
Additive to the leading
electrolyte
-
pH
3.55
3.55
ca.3
Cl
−
Cl
−
CITR
b
2
Anion
Concentration (mmol L
−1
)
1
1
1
H
+
H
+
H
+
Counter ion
0.1%HEC
d
0.1%HEC
d
Additive to the leading
electrolyte
pH
3.0
3.0
ca.3
a
β-alanine
b
Citric acid
c
Abbreviations: BALA=β-alanine; CITR=citric acid; BTP=aminopropane, 1, 3-bis-tris(hydroxy-
methyl)methyl-aminopropane
d
HEC=Hydroxyethylcellulose
Source: Reproduced with permission from Elsevier Science [47]
respect to the determinations of micro constituents. In a search for optimal separating
conditions, operational system No.2 (Table 14.2) was used for the determinations of
microconstituents.
As only anionic constituents of relatively strong acids can achieve the effective
mobilities within the chloride phosphate mobility interval at low pH, the number of
possible interfering constituents (eg organic anions associated with biological processes
in water) is also reduced using the proposed operational systems.
Some typical results obtained by applying the isotachophoretic technique to river water
samples are shown in Tables 14.3 and 14.4.
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