14
15
XII.
XII.
XII.
XII.
XII. Other Measurement T
Other Measurement T
Other Measurement T
Other Measurement T
Other Measurement Techniques
echniques
echniques
echniques
echniques
Known addition (for F
-
)
An unknown concentration can be determined by adding a
known amount (volume and concentration) of measured
ion to a known volume of the sample. This technique is
useful for very low F
-
concentration samples. It can use an
ideal sensor slope, but actual determined slopes at the
temperature of measurement should be used if known.
This method is preprogrammed in the Hanna HI 4222 pH/
ISE/mV meter, which simplifies the method greatly.
Example: Fluoride ion determination with known addition.
1. A 50 mL sample of unknown (Vsample) is placed in
a clean plastic beaker with cleaned electrodes. The
mV 1 is recorded. If fluoride metal complexes are
present add 50 mL TISAB II (V
TISAB
). Mix well then
take mV value.
2. 5 mL (Vstd) of 10
-3
M (Cstd) standard is added to the
beaker and the mV value decreases. The unknown
fluoride concentration in the original sample
(Csample) can then be determined by the following
equation.
3. The procedure can be repeated with a second stan-
dard addition to verify slope and operation of the
method.
Five mL acetate buffer (3.7 M HOAC/0.76M 0AC
-
in
composition) is added to 100 mL of sample. A standard
aluminum solution is first titrated with a fluoride solution
to determine the endpoint value. Measurements may be
automated by use of the Hanna Titrator HI 901 or titrated
manually.
XIII.
XIII.
XIII.
XIII.
XIII.
The HI 4110 and HI 4010 sensors measure fluoride ions
between 5 and 8 pH.
XIV.
XIV.
XIV.
XIV.
XIV. Storage and Care of the HI 4010 and
Storage and Care of the HI 4010 and
Storage and Care of the HI 4010 and
Storage and Care of the HI 4010 and
Storage and Care of the HI 4010 and
HI 4110 sensors
HI 4110 sensors
HI 4110 sensors
HI 4110 sensors
HI 4110 sensors
The HI 4010 sensor can be stored in standards near
measured values for short periods of time and should be
stored dry with the protective cap on when not in use for
long periods of time. The model HI 4110 combination
electrode can be left in standards that were used for
calibration for short time periods. If the electrode will be
used frequently and needs to be ready for use, take measures
to prevent evaporation of fill solution. Top off fill solution,
and replace o-ring and plug on fill hole opening. Place
sensor tip in a dilute fluoride standard, positioned upright.
Prior to use, drain electolyte chamber and refill with fresh
fill solution.
For long term storage, the electrode should be drained,
disassembled and washed of salts with deionized water.
Wrap the ceramic junction in Parafilm
®
or other sealing
wrap. Unscrew the fluoride module and store dry in the
shipping vial. Store disassembled electrode in storage box
provided with electrode.
XV.
XV.
XV.
XV.
XV.
For F
For F
For F
For F
For F
-----
Multiply by
Multiply by
Multiply by
Multiply by
Multiply by
Moles/Liter (M) to ppm (mg/L)
1.900 x 10
4
ppm (mg/L) to M (Moles/Liter)
5.263 x 10
-5
(
V
sample
+
V
standard
+
V
ISA
)=
V
T
(
V
sample
+
V
ISA
)=
V
S
’
C
sample
=
(
V
T
)10
∆
E/S
- (
V
S
’
)
C
standard
V
standard
V
sample
V
S
’
Titration
Titration can be used to measure an ion that doesn
’
t
have an ion selective sensor. An example of this is the use
of the Hanna HI 4110 or HI 4010 fluoride electrode for
aluminum (Al
3+
)
determination. Because the
stoichiometry between the two species is variable fixing
the pH and titrating to a fixed endpoint is advised.
pH
pH
pH
pH
pH
Conversion tables
Conversion tables
Conversion tables
Conversion tables
Conversion tables
