Instruction Manual
HI 4114
POTASSIUM
COMBINATION
HI
4000-50
SENSOR HANDLE
HI 4014HI 4014
HI 4014
HI 4014HI 4014
HI 4114HI 4114
HI 4114
HI 4114HI 4114
Potassium Ion
Selective Electrode
Half-cell
Combination
1
HI 4014 PHI 4014 P
HI 4014 P
HI 4014 PHI 4014 P
HI 4114 PHI 4114 P
HI 4114 P
HI 4114 PHI 4114 P
I.I.
I.
I.I.
The Hanna HI 4014 and HI4114 are ion selective elec-
otassium half-cellotassium half-cell
otassium half-cell
otassium half-cellotassium half-cell
otassium combination electrodeotassium combination electrode
otassium combination electrode
otassium combination electrodeotassium combination electrode
IntroductionIntroduction
Introduction
IntroductionIntroduction
trodes designed for the measurement of potassium ions in
aqueous solutions. They utilize a replaceable sensing module that contains an organic polymer membrane that is
sensitive to potassium. HI 4014 is a half-cell electrode that
requires a separate reference.
HI 4114 is a combination ion selective electrode.
IIII
SpecificationsSpecifications
II.
Specifications
IIII
SpecificationsSpecifications
Type: PVC membrane with
organic ion exchanger
Ion measured: Potassium (K+)
Measurement range: 1M to 1X 10-6M
39100 to 0.039ppm
Interference:
Organic solvents andcationic detergents must be absent.
Ratio of interfering ion to K+ must be below
10 for NH
300 for Li
2000 for Na
2000 for Ca
+
4
+
+
2+
Operating Temperature: 0-40°C
III.III.
Theory of Operation:Theory of Operation:
III.
Theory of Operation:
III.III.
Theory of Operation:Theory of Operation:
The HI 4014 and HI 4114 potassium electrodes are potentiometric devices used for the rapid determination of free
potassium ions in water, soft drinks, wine, and soils. The
electrode functions as a sensor or ionic conductor. HI 4014
requires a separate reference electrode to complete its electrolytic circuit. HI 4114 is a combination electrode with a
reference electrode incorporated in its design. The PVC membrane used on the sensor is impregnated with the organic
ion exchanger valinomycin. This carrier ionophore encloses
the ion like a cage. The outside of the ionophore molecule
is uncharged and it can freely diffuse through the lipid
layers of the membrane producing a charge imbalance
between the test solution and internal cell of the sensor.
This produces a voltage that changes in response to the
sample’s ion activity. When the ionic strength of the sample
is fixed, the voltage is proportional to the concentration of
potassium ions in solution. The sensor follows the Nernst
Equation:
E = E
+ 2.3 RT/nF log A
a
ion
E = observed potential
Ea = Reference and fixed internal voltages
R = gas constant (8.314 J/K Mol)
n= Charge on ion (equivalents/mol) (1+)
Operating pH: 1.5 to 12.0 pH
Dimensions: 12 mm (OD)(0.47”) X
120 mm (4.72”)
(insertion)
Connection: BNC
2
A
= ion activity in sample
ion
T = absolute temperature in K
F = Faraday constant (9.648 x 104 C/equivalent)
3
IV. IV.
Design elements of the HI 4014 and HI 4114Design elements of the HI 4014 and HI 4114
IV.
Design elements of the HI 4014 and HI 4114
IV. IV.
Design elements of the HI 4014 and HI 4114Design elements of the HI 4014 and HI 4114
electrodeselectrodes
electrodes
electrodeselectrodes
Cap
HI
4000-50
HANDLE
R
SENSO
Sensor
Handle
O-Ring
V. V.
Equipment Required:Equipment Required:
V.
Equipment Required:
V. V.
Equipment Required:Equipment Required:
• HI 4014 requires the Hanna HI 5315 Double Junction
reference electrode with HI 7076 as external electrolyte.
• 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 (ion) meter is not available).
• Hanna HI 180 magnetic stirrer or equivalent with
magnetic stirring bars (Note: Isolate beakers from stirrer motor heat by placing insulating material such as
foam or cork between them).
• Hanna HI 76404 electrode holder or equivalent.
• Plastic beakers ( HI 740036P) or other suitable mea-
surement vessel.
Sensing
module
Upper Cap
Upper
Threads
O-Ring
Ceramic Junction
on Inner Stem
Liquid junction
Spring
Fill Hole
O-Ring and
Plug
Outer Sleeve
Sensing Module
VI. VI.
Solutions Required for PSolutions Required for P
VI.
Solutions Required for P
VI. VI.
Solutions Required for PSolutions Required for P
mentsments
ments
mentsments
0.1 M potassium standard, 500 mL
Ionic Strength Adjuster, 500 mL
otassium Measure-otassium Measure-
otassium Measure-
otassium Measure-otassium Measure-
HI 4014-01HI 4014-01
HI 4014-01
HI 4014-01HI 4014-01
HI 4014-00HI 4014-00
HI 4014-00
HI 4014-00HI 4014-00
Using volumetric pipettes and glassware make dilutions to
bracket the concentration of the samples. Standards with
concentrations <10
-3
M should be prepared daily.
Store standards in plastic bottles. Add 2 mL of Hanna ISA
HI 4014-00 to 100 mL sample or standard.
4
5
VIIVII
General GuidelinesGeneral Guidelines
VII.
General Guidelines
VIIVII
General GuidelinesGeneral Guidelines
• Ensure the o-ring is installed on modules before screw-
ing into the sensor handle or inner stem.
O-Ring
• Due to shipping or storage the internal solution inside
the sensing modules may have developed an air
pocket near the membrane. Gently shaking the sensor
down (like the old style mercury thermometers) will
place the internal solution next to the membrane.
• Presoaking the potassium sensor in a 10
-2
M standard
for at least half-hour before calibration will help to
optimize the sensor response.
• Calibration standards and sample solutions should
have the same ionic strength. ISA should be added to
both samples and standards in the same ratios.
• Calibration standards and sample solutions should
be at the same temperature.
• Thermally insulate solution vessel from magnetic stir-
rer.
• Calibration standards and sample solutions should
be stirred at the same rate using identically sized TFE
coated stir bars.
• Rinse electrode pair with distilled or deionized water
between samples and dab dry with lab wipe or other
soft disposable absorbent toweling. Do not rub membranes.
• Check for gas bubbles that may form near the sensing
surface (due to temperature changes). Tap off gently.
• Avoid large changes in temperature (thermal shock)
as it may damage the sensor.
Additional HI 4114 Guidelines
• Remove the protective plastic wrap that covers the
ceramic junction before assembling sensor for the first
time.
• Add reference fill solution HI 7076 to bottom of fill
hole or empty and refill solution daily before using.
• During measurement always operate electrode with
the fill hole open.
• During normal use, fill solution will slowly drain out
of the tapered cone junction at the lower portion of the
electrode. Excessive loss (>4 cm drop within 24 hours)
is not normal. If this occurs verify cap is tightened and
the interface between the internal cone and outer
body is free of debris.
• Add filling solution daily to maintain a good head
pressure. For optimum response, this level should be
maintained and not be allowed to drop more than 2
-3 cm (1-inch) below fill hole.
• Do not use an electrode if crystallized salts are visible
inside the electrode. Drain electrode, disassemble and
rinse internal body with deionized water. Reassemble
and refill with fresh fill solution.
• If an erratic measurement occurs, check to see if for-
eign matter is seen trapped near the internal cone.
Drain by depressing the electrode cap then refill with
fresh fill solution.
VIII.VIII.
Electrode PreparationElectrode Preparation
VIII.
Electrode Preparation
VIII.VIII.
Electrode PreparationElectrode Preparation
HI 4014
The Hanna HI 4014 is a 2 piece design comprised of a
sensor handle (HI 4050) and a sensing module (HI 4014-
51).
1) Remove sensing module from shipping vial. Do not
touch the sensing membrane with the “H” hole pattern on it.
2) Screw the module into the sensor handle finger tight.
Do not over tighten.
6
7
HI
4000-50
E
L
D
N
A
H
R
O
S
N
E
S
3) Holding the assembled electrode at the cable end,
shake the sensor to ensure internal fill solution that
may have separated during shipping is in contact
with inner membrane surface.
4) Prepare reference electrode by filling outer electrolyte
reservoir with fill solution HI 7076.
5) Place sensor (and reference) electrodes into electrode
holder and connect cable connectors to meter.
6) Soak the potassium membrane in a potassium containing standard for a hour before calibration.
Remove
Water
Deionized
Parafilm
®
4. Rinse inner stem with deionized water making certain
to wet o-ring found on the inner stem.
5. Reassemble electrode by gently pushing the inner
assembly into the outer body, sliding spring down
cable, and screwing cap into place.
6. Remove fill hole cover and o-ring on fill hole spout.
Using the dropper pipette provided, add a few drops
HI 7076 fill solution to the electrode, wetting the oring and rinsing out the fill solution chamber.
HI 4114
The Hanna HI 4114 is shipped dissembled.
1. Unwrap Parafilm® seal found over ceramic junction
on inner stem and discard. This is only used for shipping and long term storage.
2. Open the glass vial (HI 4114-51) and remove the
potassium sensing cone. Do not touch the sensing
membrane with the “H” hole pattern on it.
3. Ensure o-ring is installed on module before screwing
the cone into the inner stem finger tight. Do not over
tighten.
8
9
7.
Holding the body of the electrode gently press the
upper cap with your thumb. This permits the fill solu-
tion to drain out of the body.
8.
Release the cap and verify electrode returns to its
original position. (You may need to gently assist for
this to occur).
COMBINATION
POTASSIUM
HI 4114
9. Tighten the electrode cap onto the body and fill electrode body until fill solution volume is just below fill
hole.
10. Position electrode in a Hanna HI 76404 electrode
holder (or equivalent) and connect BNC connector to
meter.
IX. IX.
Quick Check of Electrode SlopeQuick Check of Electrode Slope
IX.
Quick Check of Electrode Slope
IX. IX.
Quick Check of Electrode SlopeQuick Check of Electrode Slope
• Connect electrode(s) to pH/mV/ISE meter.
• Place meter in mV mode.
• Place 100 mL of deionized water into a beaker with
stir bar.
• Place reference and measuring half-cell or combina-
tion electrode into prepared sample.
• Add 1 mL of a standard to beaker. Record the mV
value when stable.
• Add an additional 10 mL of standard to the solution.
Record the mV when reading has stabilized. This
10
value should be more than the previous value noted
(more positive).
• Determine the difference between the two mV values.
An acceptable value for this slope is
56 ± 4 mV at typical room temperatures
(20-25°C).
X. X.
Corrective ActionCorrective Action
X.
Corrective Action
X. X.
Corrective ActionCorrective Action
• Verify module has been screwed into sensor handle or
inner stem.
• Verify seal has been removed from ceramic junction
(HI 4114) or HI 5315 reference electrode.
• Verify electrodes are connected properly to meter and
meter is powered.
• Verify dilute standards are freshly made and stored.
Remake solutions if appropriate. Store in plastic
bottles.
• If the reading is unstable, shake sensor down (see
Section VII).
• If the sensor slope just misses the suggested slope
window, soaking the sensor in a standard may solve
the problem.
• If the membrane is damaged, the response becomes
extremely sluggish, or the slope of the electrode has
decreased significantly, and procedures above have
not helped, the modules should be replaced.
Module replacement for HI 4014
1. Dry off module and sensor handle.
2. Unscrew sensing module and replace with a new one.
(HI 4014-51).
3. Soak new assembled module in potassium solution
to condition it before calibration.
Module replacement for HI 4114
1. Drain the fill solution by depressing cap. Rinse electrode with distilled or deionized water. Drain.
2.
Unscrew upper cap and slide down cable toward
connector.
3. Move spring and outer body down cable also.
4. Dry off inner stem and module with a soft tissue.
11
5. Hold inner stem and unscrew module and replace
V
with a new one. (HI 4114-51).
6. Reassemble electrode (see section VII), and refill with
electrolyte. Soak new membrane in potassium solution to condition before calibration.
XIXI
Direct Calibration and MeasurementDirect Calibration and Measurement
XI.
Direct Calibration and Measurement
XIXI
Direct Calibration and MeasurementDirect Calibration and Measurement
This method is a simple procedure for measuring many
samples. A direct reading ISE meter (HI 4222 or equivalent) determines concentration of the unknown by a direct
reading after calibrating the meter with the standards. HI
4014-00 ISE is added to both samples and standards to
adjust the ionic strength of the solutions at a dose of 2 mL
per 100 mL standard or sample. The meter is calibrated
with freshly made standards that are in the measurement
range of the unknowns. Unknowns are then read directly.
In the non-linear region, more calibration standards are
required and more frequent calibrations are advised.
A pH/mV meter in mV mode and semi log graph paper
may also be used. Two or more freshly prepared standards
that are in the measurement range of the unknowns (with
ISA added), are measured in mV mode on the meter.
These values are plotted on semi-log paper and the points
are connected to form a straight-line curve. When samples
are measured, their mV values are converted to concentration by following the mV to the concentration axis on the
semi-log plot.
Procedure:
Follow sections VIII and IX to prepare electrodes for measurement.
1) Follow section VI to prepare standards/ solution. Stan-
dards should bracket and fall within the range of
interest. Standards and solutions should be at the
same temperature.
2 mL of HI 4014-00 is added to 100 mL of
both samples and standards. Add stir bar and mix
before taking measurements.
2) Follow section VII; General Guidelines to optimize test
set-up.
3) During calibration it is best to start with lower concentration samples first. Wait for a stable reading before
reading/ recording values. Permit longer equilibration at these levels (3 or 4 minutes).
4) To prevent carry over and contamination of samples,
rinse sensors with deionized water and dab dry between samples. Do not rub membrane.
Typical HI 4014 and HI 4114 Linearity
90
40
-10
m
-60
-110
-160
123456
-Log of Concentration
12
13
XII. XII.
Other Measurement TOther Measurement T
XII.
Other Measurement T
XII. XII.
Other Measurement TOther Measurement T
Known additionKnown addition
Known addition
Known additionKnown addition
echniquesechniques
echniques
echniquesechniques
An unknown concentration can be determined by adding a
known amount (volume and concentration) of K+ standard
to the sample. mV values are noted before and after the
addition of standard (∆E). An ideal sensor slope can be
used in the equation but actual determined slopes at the
temperature of measurement should be used if known (S).
This method is preprogrammed in the Hanna HI 4222 pH/
ISE/mV meter, which greatly simplifies the method .
Example:
Potassium ion determination with known addition.
1. A 50 mL sample of unknown (V
) is placed in an
SAMPLE
clean plastic beaker with a thoroughly cleaned electrode (s). Add 1 mL of ISA to sample. Mix. The mV1 is
recorded.
2. 5 mL (V
) of 10-1M (C
STD
) standard is added to the
STD
beaker and the mV value increases. (Note: for other
concentration samples, add a known volume and
concentration of standard to produce approximately
30 mV change).
3. The unknown potassium concentration in the original
sample (C
) can then be determined by using the
SAMPLE
equation that follows.
The procedure can be repeated with a second standard
addition to verify slope and operation of the method.
C
sample
=
C
standardVstandard
(V
)10
T
∆E/ S
- (VS’)
V
V
S’
sample
XIII. XIII.
pHpH
XIII.
pH
XIII. XIII.
pHpH
HI 4014/ HI 4114 potassium electrodes operate over a wide
pH range. The pH range 1.5 - 12 is acceptable for
measurements. Samples and standards can be adjusted to
be within the working pH range.
XIV. XIV.
Storage and Care of the HI 4014 sensor andStorage and Care of the HI 4014 sensor and
XIV.
Storage and Care of the HI 4014 sensor and
XIV. XIV.
Storage and Care of the HI 4014 sensor andStorage and Care of the HI 4014 sensor and
HI 4114 electrodeHI 4114 electrode
HI 4114 electrode
HI 4114 electrodeHI 4114 electrode
HI 4014 sensor can be stored in dilute standards near the
sample concentration for short periods of time and should
be disassembled and stored dry in the shipping vial when
not in use for long periods of time. Do not expose module to
elevated temperatures. Refrigeration of module will extend
life time.
HI 4114 combination electrode can be left in dilute standards near the sample concentration for short periods of
time. 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, replace o-ring, fill hole
cover on the fill hole opening, and place in dilute potassium solution. Store electrode upright. Before using, flush
junction once and top off fill solution.
For long-term storage, disassemble electrode and wash all
salts from assembly with deionized water. Wrap ceramic
junction on inner stem in Parafilm® or other sealing film.
Unscrew module from the inner stem and blot dry. Store
module in shipping vial. Store electrode assembly disassembled. Do not expose module to elevated temperatures.
Refrigeration of module will extend its life.
(V
sampl e+Vstandar d+VISA
(V
sampl e+VISA
14
)= V
)= V
S’
T
XVXV
. .
Conversion TConversion T
XV
.
Conversion T
XVXV
. .
Conversion TConversion T
ablesables
ables
ablesables
Multiply by Multiply by
Multiply by
Multiply by Multiply by
Moles/L (M) K+ to ppm K+ (mg/L) 39100
-5-5
-5
ppm K+ (mg/L) to M K+(Moles/L) 2.56 X 10
15
-5-5
MAN4114 07/06 REV3
WARRANTY WARRANTY
WARRANTY
WARRANTY WARRANTY
Hanna Instruments Ion Selective Electrodes are warranted
to be free of defects in material and workmanship for 6
months from date of purchase when used for their intended
purpose and maintained according to instructions. If they
fail to work when first used contact your dealer immediately.
Damage due to accidents, misuse, misapplication, tampering
or lack of prescribed maintenance is not covered.
Hanna Instruments reserves the right to modify the design,
construction or appearance of its products without advance
notice.
16
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