Hanna Instruments HI 4101 Instruction Manual
HI 4101
AMMONIA
Instruction Manual
HI 4101HI 4101
HI 4101
HI 4101HI 4101
Ammonia
Ion
Selective Electrode
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HI 4101 Ammonia ElectrodeHI 4101 Ammonia Electrode
HI 4101 Ammonia Electrode
HI 4101 Ammonia ElectrodeHI 4101 Ammonia Electrode
I. I.
Introduction:Introduction:
I.
Introduction:
I. I.
Introduction:Introduction:
The Hanna HI 4101 Ammonia gas selective electrode is a
combination electrode designed for the measurement of
ammonia in aqueous solutions such as waste water samples,
wine, beer. Ammonium ions are also measured by conversion to ammonia gas upon ISA addition.
II.II.
SpecificationsSpecifications
II.
Specifications
II.II.
SpecificationsSpecifications
Type: NH3 gas sensing
electrode with glass pH
internal, Ag/ AgCl
reference and gas
permeable PTFE
membrane.
Species Measured: NH
+
, NH
4
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Measurement Range: 1.0 M to 1x 10-6M
17000 to 0.02 ppm
Interfering ions: Surfactants, wetting
agents, volatile amines.
Operating Temperature: 0 to 40°C
Operating pH: >11 pH
Dimensions: 12 mm (OD) X 120
mm (insertion)
0.47”x 4.72”
Wetted materials: Delrin®, body and cap
PTFE gas membrane
Connection: BNC
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III.III.
Theory of OperationTheory of Operation
III.
Theory of Operation
III.III.
Theory of OperationTheory of Operation
::
:
::
The ammonia 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 ion-containing electrolyte, and are isolated from the sample by a
gas permeable membrane made of polytetrafluoroethylene
(PTFE).
Dissolved gas in the sample solution diffuses into the membrane and changes the pH in the thin film of electrolyte on
the surface of the pH glass. Diffusion continues until the
partial pressures of the gas in the sample and thin film are
equal. The change in pH is proportional to the concentration of dissolved gas in the sample solution.
The Nernst expression for an ammonia sensor is expressed
in the equation below. Note that the potential is a function
of the ammonia gas, which in turn is related to the hydroxyl
ion concentration. The glass internal, Ag/AgCl reference,
and Henry’s law constant are rolled into the E’ and E
constants. The Nernst equation for the sensor becomes the
equation noted below:
o
E = E’–2.3RT/nF log [A]= Eo–0.059 log [OH-]
E = observed potential
E’ = Reference and fixed internal voltages
R = gas constant (8.314 J/K Mol)
n= Charge on ion (equivalents/mol)
A
= ion activity in sample
ion
T = absolute temperature in K
F = Faraday constant (9.648 x 104 C/equivalent)
The mV should decrease in a Nernstian manner as the
ammonia partial pressure increases in the sample.
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IV.IV.
Design ElementsDesign Elements
IV.
Design Elements
IV.IV.
Design ElementsDesign Elements
The Hanna HI 4101 ammonia 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
pH
sensitive
membrane
membrane/membrane cap
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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): HI 4001-00
Hanna 0.1 M standard: HI 4001-01
Hanna 100 ppm N standard: HI 4001-02*
Hanna 1000 ppm N standard: HI 4001-03*
*Please Note: These calibration standards are ppm as
NH3-N.
See Section XVII for additional solutions used for maintenance.
Using volumetric pipettes and glassware make dilutions of
the standard to bracket the concentration of the samples.
Standards with concentrations less than 10-3M should be
prepared fresh daily. Store solution in a tightly sealed
bottle without ISA added. 2 mL of HI 4001-00 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 11 thus converting ammonium ion
to ammonia. It also provides samples and standards a
constant ionic strength background that stabilizes the solutions activity coefficient and permits concentration to be
measured directly. The ISA provides color indication to verify
it has been added to the solution and a complexing agent
to remove metal ions (i.e copper, zinc) from solution. These
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