Omega Products ISE-8882 Installation Manual
OMEGA ENGINEERING
ISE-8882 ION SELECTIVE ELECTRODE FOR SURFACTANT
INSTRUCTION MANUAL
GENERAL INSTRUCTIONS
Introduction
The Omega ISE-8882 Surfactant Electrode indicates the potentiometric endpoint when titrating
anionic or
cationic
surfactants in solution. Titration procedures for manual titrations are discussed
in this manual, though adaptation to automatic titration techniques is quite simple. The electrode
0.05M
comes packaged with one 50 ml bottle of
O.OlM
one 50 ml bottle of
sodium lauryl sulfate (sodium dodecyl sulfate) titrant, and one 50 ml
Hyamine 1622 (benzethonium chloride) titrant,
bottle of sample additive, diluted Triton X- 100.
Required Equipment
1.
2.
3.
A
pH/mV meter, either line operated or portable.
A hand controlled delivery system, such as a 10 ml
ISE-8882 Surfactant Electrode (glass)
Required Solutions
1.
2.
Distilled or de-ionized water to prepare all solutions and standards.
Titrant for the titration of anionic surfactants is Hyamine 1622,
To prepare this titrant from your own laboratory stock, add 22.405 grams of
Hyamine 1622 and 5 ml of 1 M
de-ionized water. Swirl the flask to dissolve the solid and fill to the mark with
distilled water. Cap the flask and invert several times to mix the solution.
3.
Titrant for the titration of
(SLS) To prepare this titrant from your own laboratory stock, add 2.883 grams
sodium lauryl sulfate (SLS) to a one liter volumetric flask about half full of distilled
water. Swirl the flask to dissolve the solid and fill to the mark with distilled water.
Cap the flask and invert several times to mix the solution.
pipet
or burette.
0.05M
NaOH to a 1 liter volumetric flask about half full of
O.OlM
cationic
surfactants is
Sodium Lauryl Sulfate
3.
Sample Additive, diluted Triton X- 100, to keep electrodes clean when added to all
samples. To prepare, add 10 ml of reagent-grade Triton X-100 to a one liter volumetric
flask about half full of distilled water. Cap the flask and invert several times to mix the
solution.
4.
Electrode Filling Solution, 4M KC1 (with
Ag’), for filling the reference chamber of
the electrode.
5.
6.
(O.OlM
(O.lM HCl) and polyacrylates
NaOH).
Electrode Rinse Solutions consisting of about 50 ml 0.
for acidic rinse (anionic or
cationic
surfactant analysis) and 50 ml 0.
cationic
HCl diluted to 1000 ml
1M
1M
surfactantspH of both anionic and pH Adjuster Solutions for adjusting the
NaOH
diluted to 1000 ml for alkaline rinse (polyacrylate analysis).
GENERAL PREPARATION
Electrode Preparation
Remove the rubber cap(s) covering the electrode tip(s) and the rubber insert covering the filling
hole of the reference electrode. Fill the combination electrode or the reference electrode with the
filling solution shipped with the electrode to a level just below the fill hole. No preparation is
required with a sealed reference electrode. Gently shake the electrode downward in the same
manner as a clinical thermometer to remove any air bubbles which might be trapped behind the
surfactant membrane.
O.OlM
Prepare
O.OOOlM
SLS by diluting 1 ml of the
first usage, or after long-term storage, soak the tip of the surfactant electrode in
SLS to 100 ml with distilled water. Prior to
O.OOOlM
SLS for
10 minutes before using the electrode each day. Use fresh solution daily. The electrode is now
ready for use.
Connect the electrode(s) to the proper terminal(s) as recommended by the meter manufacturer.
If the stock solution becomes cloudy or contaminated in any way, discard it.
Titrant Preparation
Based on the recommendations found in
Required Solutions,
select an appropriate titrant.
Determine the concentration of titrant needed for the analysis from Table 1.
TABLE 1: Recommended Titrant Concentrations
Recommended Titrant
Concentration
(M)
Expected Sample
Concentration
(M)
0.05 0.050 to 0.001
0.005 0.001 to 0.0001
0.001
0.0001 to 0.00001
The titrant concentration may need to be adjusted depending on the concentration of the sample and
the method of titration in use. Use the formula:
~&_.Ys_
Vt
Ct
=
Ct
where:
= concentration of titrant
C,
= concentration of sample
V, = volume of sample
Vt
= volume of titrant
For example, for the titration of anionic surfactants, dilute the
0.05M Hyamine 1622 solution
provided to the appropriate concentration as calculated above.
Titrate against a known concentration of SLS to standardize the titrant. Calculate the exact
concentration of the titrant using the same formula given above.
Units of Measurement
Any convenient unit of measurement may be used for the result. Units may be chosen for samples
measured in volume or weight.
If doing the titrations with an automatic titrator, note whether specific units must be entered for the
titrant and/or specific units are required for the result.
Measuring Hints
The sensing membrane is normally subject to water uptake and might appear milky.This has no
effect on performance.
All samples and standard should be at ambient temperature for precise measurement.
3
Constant, but not violent, stirring is necessary for accurate measurement. Slow stirring is
recommended to avoid foaming.
Always rinse the electrode tip(s) with the slightly acidic (or alkaline) rinse solution described in
Required Solutions
and blot dry with a fresh tissue between titrations to prevent solution
carryover.
Check the electrode for air bubbles adhering to the membrane surface after immersion in solution.
Agitate the electrode gently to remove any air bubbles.
A slow or sluggish electrode response may indicate surface contamination of the electrode
membrane. Soak the electrode tip in distilled water for about 5 minutes to clean the membrane.
Rinse the membrane and soak in
O.OOOlM
SLS for about 5 minutes to restore performance.
The electrode should be reconditioned daily before storage as described in
Cleaning,
Reconditioning, and Storage.
Sample Requirements
To help keep the electrode clean and working properly, add sample additive, diluted Triton X- 100,
to all samples. For every 50 ml of sample, use 1 ml of sample additive.
Samples should be diluted to approximately
10m5
to
lOA
M to help preserve electrode life, help
avoid foaming during the titration, and help improve long term results.
pH
Adjust the
of the sample depending on the method being used.
Anionic surfactants, as well as sulfated and sulfonated surfactants, may be titrated with Hyamine
1622. Adjustment to
Polyacrylates should be adjusted to
Cationic
acidification to
surfactants should be titrated with an anionic reagent, such as sodium lauryl sulfate,
O.OlM
HCl.
pH 3 with
pH
1 O-l 1 with 0.
O.OlM
1M
NaOH before analysis.
HCl.
pH 2.5-4.5 should be done by addition of
after
ANALYTICAL PROCEDURES
Sample Analysis
For potentiometric endpoint determination, the surfactant electrode is used as an endpoint indicator.
An example of the titration procedure is illustrated using the analysis of an anionic surfactant as an
example.
2.
3.
1.
Using the acid rinse solution, rinse the surfactant electrode and blot dry with a soft,
lint-free tissue before the titration. Fill the single junction reference electrode, or the
reference chamber of the combination electrode with fresh filling solution to a level
just below the fill hole.
Assure that the electrodes are plugged into the
mV mode. To prevent air entrapment, mount the electrode at a 20 ” angle from
the
pipet,
the vertical. Using a
O.OlM
Add 3 ml of
HCl
add 50 ml of the unknown sample to a 150 ml beaker.
and 1 ml of the sample additive, diluted Triton X-100.
pH/mV meter and that the meter is in
Place the beaker on a magnetic stirrer, and start stirring at a constant, but moderate,
rate.
Lower the electrodes into the solution so that the tips are completely covered
+l
and wait until the
to 2 drift is mV reading is stable,
mV/minute, before adding
any titrant. Remove any bubbles by re-dipping electrode.
Add
0.05M Hyamine 1622 titrant to a 10 ml buret until filled. Once
t&rant
has been reached, add the
in 0.5-l .O ml increments at the beginning of the
titration, and in increments of 0.1-0.25 ml in the region of the endpoint.
mV stability
The
endpoint is at that volume of titrant where the potential changes dramatically with
the slightest addition of titrant. The electrode potential should be recorded after
each addition of titrant. Continue titrating until 1 or 2 ml past the endpoint. On
standard coordinate graph paper, plot milliliters of titrant added versus
mV reading.
The endpoint is the point of greatest inflection. Calculate the unknown surfactant
concentration:
Vtitrant
X
unknown
Of
theunknown
where:
C
unknown
=
&horn
Ctibant
Vtibant
Vunknown
=COnCenkitiOn
=
concentration of the titrant
=
volume of the titrant in milliliters
= volume of the unknown in milliliters
Ctitmt
V
Depending on sample concentration and method used, this basic procedure may need modification
Loading...