Hanna Instruments HI4105 User Manual
HI 4105
DIOXIDE
CARBON
Instruction Manual
HI 4105HI 4105
HI 4105
HI 4105HI 4105
Carbon Dioxide
Ion
Selective Electrode
1
2
HI 4105 Carbon Dioxide ElectrodeHI 4105 Carbon Dioxide Electrode
HI 4105 Carbon Dioxide Electrode
HI 4105 Carbon Dioxide ElectrodeHI 4105 Carbon Dioxide Electrode
I. I.
Introduction:Introduction:
I.
Introduction:
I. I.
Introduction:Introduction:
The Hanna HI 4105 Carbon Dioxide gas sensing electrode
is a combination electrode designed for the measurement
of Carbon Dioxide in aqueous solutions such as water, soft
drinks or wine, samples. Carbonate and Bicarbonate ions
are also measured by conversion to Carbon Dioxide gas
upon ISA addition.
II.II.
SpecificationsSpecifications
II.
Specifications
II.II.
SpecificationsSpecifications
Type: CO2 gas sensing
electrode with glass pH
internal, Ag/ AgCl
reference and gas
permeable membrane.
2-
Species detected: CO
-
,HCO
, CO
3
3
2
CO2 Measurement Range: 0.02 M to 4 x 10-4M
880 to 17.6 ppm
2-
Interfering ions: SO2/SO
3
, H2S/S
2-
Operating Temperature: 0 to 40°C
Operating pH: 4-5 pH
Dimensions: 12 mm (OD) X 120
mm (insertion)
0.47”x 4.72”
Wetted materials: Delrin®, body and cap
with PTFE membrane
Connection: BNC
3
III.III.
Theory of OperationTheory of Operation
III.
Theory of Operation
III.III.
Theory of OperationTheory of Operation
::
:
::
The Carbon Dioxide electrode is a complete potentiometric
cell that contains both a silver/silver chloride (Ag/AgCl)
reference and a pH measurement element. These elements
are housed within a thermoplastic body in a chloride ioncontaining electrolyte, and are isolated from the sample by
a PTFE membrane.
ISA addition changes the pH of the sample to approximately 4.7 pH and Bicarbonate (HCO
2-
(CO
) ions in the sample are converted to carbon dioxide
3
-
) and carbonate
3
(CO2). The CO2 in the sample solution diffuses through the
PTFE membrane where it dissolves into the thin film of fill
solution found between the membrane and the internal pH
membrane. Here it converts back into bicarbonate and
hydrogen ions. The pH changes proportionally with the
concentration of dissolved gas in the sample solution. Diffusion of CO2 continues until the partial pressures of the gas
in the sample and thin film are equal.
The Nernst expression for an Carbon Dioxide sensor is expressed in the equation below. Note that the potential is a
function of the Carbon Dioxide gas, which in turn is related
to the hydrogen ion concentration. The glass internal,
Ag/AgCl reference, equilibrium constant and Henry’s law
constant are rolled into the E’ and Eo terms. The Nernst
equation for the sensor becomes the equation noted below:
E = E’+2.3RT/nF log [CO2]= Eo+0.059 log [H+]
E = observed potential
E’ = Reference and fixed internal voltages
R = gas constant (8.314 J/K Mol)
n= Charge on ion (equivalents/mol)
T = absolute temperature in K
4
F = Faraday constant (9.648 x 10
C/equivalent)
The mV should increase in a Nernstian manner as the
carbon dioxide partial pressure increases in the sample.
4
IV.IV.
Design ElementsDesign Elements
IV.
Design Elements
IV.IV.
Design ElementsDesign Elements
The Hanna HI 4105 Carbon Dioxide gas sensor has 3 main
parts. These are the membrane/membrane cap, outer probe
body with antirotation key and the pH/reference assembly
which includes the outer electrode cap, spring, inner cap
and pH/reference electrode assembly.
pH/reference electrode assembly
cable
outer electrode
cap
spring
antirotation key inner cap
Outer probe body
Reference
electrode
O-ring
pH
sensitive
membrane
Membrane/membrane cap
5
V.V.
Equipment Required:Equipment Required:
V.
Equipment Required:
V.V.
Equipment Required:Equipment Required:
• Hanna HI 4222 pH/ISE/mV meter or other suitable
ion or pH/mV meter. (Note: log/linear graph paper is
useful if an ISE meter is not available).
• Hanna HI 180 magnetic stirrer or equivalent with
stirring bars. (Note: Isolate beakers from stirrer motor
heat by placing insulating material such as foam or
cork between them).
• Hanna HI 4000-71 gas sensor test vessel or
Hanna HI 76404 electrode holder or equivalent with
Beakers or other suitable measurement vessel with
plastic sealing film or wrap.
VI. VI.
Solutions Required for Calibration:Solutions Required for Calibration:
VI.
Solutions Required for Calibration:
VI. VI.
Solutions Required for Calibration:Solutions Required for Calibration:
Ionic Strength Adjuster (ISA), 500 mL: HI 4005-00
Hanna 0.1 M standard, 500 mL: HI 4005-01
Hanna 1000 ppm CO2 standard, 500 mL: HI 4005-03*
*Please Note: This calibration standards is ppm as CaCO
See Section XVII for additional solutions and accessories
used for maintenance.
3
Using volumetric pipettes and glassware prepare serial
dilutions of the standard. Select concentrations that will
approximately bracket the concentration of the samples to
be measured. Standards with concentrations less than
10-3M should be prepared fresh daily. Store solution in a
tightly sealed bottle without ISA added. 10 mL of HI 400500 ISA should be added to each 100 mL sample of standard and samples just prior to measurement. ISA adjusts
the pH of the sample or standard to about pH 4.7 thus
converting carbonate and bicarbonate ion to carbon dioxide. It also provides samples and standards a constant
ionic strength background that stabilizes the solutions activity coefficient and permits concentration to be measured
directly.
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