Using
the latest pulse current technology and our patented
“ACE” control system, (Patent No.GB2370641), the
Aquamax KF automatically selects the appropriate titration speed
dependent upon the amount of water present in the sample. The titration
speed is reduced as the end point is
approached, and when the titration is completed the instrument prints
out and displays the results.
What
are the advantages of
Coulometric Karl Fischer?
Combining coulometry with the Karl Fischer titration can provide many
advantages over the volumetric technique. The main benefits that this
coulometric technique offers include higher sensitivity, faster
titrations, no reagent calibration required and economical operation.
Indeed, unlike volumetric instruments where the solvent mixture is
normally replaced after each titration, coulometers can determine the
water content of multiple samples on one single charge of reagent.
The criteria governing reagent life are threefold:
The physical size of the titration cell usually allows for 50
– 60 ml of sample to be added. Sample volumes of 0.1
– 2.0 ml are typical for most oil and petroleum products
therefore the maximum volume of 50-60 ml is not usually a limiting
factor.
The second criteria governing reagent lifetime is the total amount of
water that can be analysed before saturation. A standard charge of
100ml anode reagent can usually analyse upto 1 gram of water.
Considering that the injected sample volume is normally quite small,
and that usually the analysis is for the determination of low levels of
water, then this water capacity should not become a limiting factor
either.
Similar to all other Karl Fischer reagents, coulometric reagents
deteriorate when left out in sunlight and with increases in
temperature. Life expectancy for one charge of reagents when left in
the titration cell can be 2-3 weeks although this is also dependent on
the total amount of sample injected and the amount of water titrated.
What
is a coulomb?
Coulombs are a measurement of current multiplied by time.
Does
sample pH have an effect?
The optimum pH range for Karl Fischer titrations is 5 – 7.
This will allow the reaction to run quickly and stoichiometrically.
Acids are produced during the titration of water and these are
neutralised by the base present in the coulometric reagent.
What
is drift?
The term Drift refers to the background moisture in the titration
vessel. This could be caused by ingress of atmospheric moisture,
chemical reactions between different samples or gradual breakdown of
the reagents. Vast majority of high drift values are caused by the
titration cell walls and generator electrodes not being cleaned and
dried sufficiently. The drift value is normally displayed in micrograms
of water per minute. This additional count is automatically subtracted
and is assumed to be constant for the duration of the titration. For
this reason, the rate of change of the drift value is more important
than the actual value itself. Although it is possible for the titrator
to be used at high drift values, it is advisable to wait until the
drift value is below 20 mg/minute, and stable, before commencing,
especially for low water content samples in the ppm ranges. The lower,
and more stable the drift – the more accurate
the result.
Must
I keep it in a fume
cupboard?
Although it is recommended that reagents are changed either in a fume
cupboard or a well ventilated area, for routine operation it is not
necessary to keep the titrator in a fume cupboard. The titration vessel
design seals the unit from ingress of atmospheric moisture.
Do
I need to be a chemist to
use one?
Many of the commercially available coulometric Karl Fischer titrators
are now becoming so complicated that a considerable skill level is
often required. However, the Aquamax KF titrators, although extremely
versatile and suitable for laboratory use, have been designed with
non-laboratory personnel in mind. Simple single button operation, easy
to assemble glassware, pre-mixed reagents, all make these titrators
suitable for almost anyone to use.
What
routine maintenance is
required? How often do I change the
septa or desiccant?
Coulometers, such as the Aquamax KF, require very little maintenance.
Ideally, the glassware should be cleaned and dried each time the
reagents are replaced but this is not always possible. Likewise, the
injection septa and possibly the desiccant should be changed
periodically. The required frequency depends on the volume of testing.
For example, a program running 100 samples per week will spend about 30
minutes per month cleaning the glassware. Otherwise there is very
little to be done.
Calibration
& overhaul
service – is this possible?
In the U.K., G.R. Scientific offer both in-house and on-site
calibration / validation services for almost all makes and models of
coulometric Karl Fischer titrators. For USA users, Penn Hills Lab
Supply offer an in-house service at their premises in Pittsburgh. This
service includes complete overhaul / cleaning of the glassware,
checking all electronic settings using calibrated equipment and
adjusting as required, replacing consumables such as septa, paper
rolls, etc, running water standards and providing a comprehensive
calibration certificate.
How
do I calibrate titrator?
You can check the performance of your titrator by periodically running
water standards such as those supplied with Cou-Lo Formula reagents.
Although in principle standardisation of a coulometer is not necessary
since the water “titrated” is a direct function of
the coulombs of electricity consumed, the ASTM methods for measuring
water content of crude oil and petroleum products stipulate that the
performance of the coulometer be regularly monitored by injecting 10
microlitre of pure water. The suggested interval is after every 10
determinations and the result obtained should be 10,000 +/- 200
microgram. The reagent should be changed if the result is outside
these limits.
Generator
electrodes
– with or without frit – which is better?
Most manufacturers use a similar configuration of titration cell in
which the anode and cathode compartments are separated by a frit
(diaphragm) and each compartment is charged with different reagents.
Some companies now offer fritless generator electrodes for use with
single solution coulometric reagents.
This combination, at first sight, seems to offer several advantages for
the operator. There is only the one reagent to be handles, easier to
charge and empty the titration vessel. Unfortunately the formulation of
single coulometric reagents are not as suitable for oil and petroleum
products as the two reagent methodology. Contact G.R. Scientific for
full information.
How
does the Aquamax deal with
interference from ambient
humidity?
This problem is effectively minimized through the Aquamax’s
unique titration vessel design and patented ACE control system
(automatically compensated errors).
What
spare parts and
accessories do
you recommend?
Reagents, sample port septa and desiccant are the only consumables.
Septa and desiccant cost very little and are replaced about once or
twice per month. It may be helpful to keep a spare set of glassware on
hand for breakage replacement.
How
does one transport the Aquamax KF
for field work?
The Aquamax KF has a built in battery, an in-car power adaptor and an
optional carry case is available. Many Aquamax KF users carry their
unit for use on the tailgate of a truck. The carry case also has a
compartment for carrying the power pack, syringes, etc.
Can I include on-site training with my Aquamax KF purchase?
Although the Aquamax KF is simple to setup and operate, some customers
choose to arrange for installation and training assistance. Our field
specialists can help create a simple and efficient moisture testing
program. Training of personnel
includes instrument setup, theory,
operation, maintenance and performance verification
techniques.
Can
I include on-site training with my Aquamax KF purchase?
Although the Aquamax KF is simple to setup and operate, some customers
choose to arrange for installation and training assistance. Our field
specialists can help create a simple and efficient moisture testing
program. Training of personnel includes instrument setup, theory,
operation, maintenance and performance verification techniques.
Do
I need to change the stirrer speed?
The toggle switch on front of the Aquamax KF enables stirrer speed to
be adjusted. However, the speed that it starts at when first switched
on is an optimum default value which we have found to be suitable for
virtually all sample types. It should not be necessary for operator to
change this setting.
Should
I turn the unit off when not in use?
It is not necessary to switch the unit off overnight but, if it is not
going to be used for several days then we suggest that it is switched
off. If it is not going to be used for two or three weeks then we
suggest emptying the titration vessel, cleaning and drying it and
assembling without replacing the reagents. On the day that you wish to
start using titrator again you can simply add the new reagent and allow
it to stabilise.
How
long will the Aquamax KF last?
Most coulometric Karl Fischer titrator manufacturers only provide a 1
or 2 year warranty. At G.R. Scientific we are extremely proud of our
manufacturing quality and workmanship, so much so that we now provide a
full 5 years parts and labour warranty totally free of charge. A
warranty certificate is enclosed with each Aquamax KF titrator.
What
are the costs for repairs?
With proper maintenance and careful handling of the glassware, repairs
are rarely necessary. Electronic and software failure occurs in less
than one instrument per 1000.
Can
I print duplicate copy of the test results?
If you are out “on-site” and wish to leave a hard
print copy of results with your customer whilst also bringing original
hard copy back to your depot, simple hold down the Start key for three
seconds and a duplicate print will be
made.
How
do I change time and date
on my unit?
This is extract from the Aquamax KF user manual;
SETTING
THE DATE AND TIME
1. Switch on the Aquamax KF and wait
for it to display the following:
2. Hold down the

key until the Aquamax KF
displays:-
3. Use the

decimal point key to move
the cursor across the screen.
4. Use the numerical keys to set / alter the required
number
5. When completed press the key to save the changes and
exit.
How
do I clean the
glassware?
Which chemicals should I / shouldn’t I use?
Under normal circumstances the titration cell can be used for a large
number of samples before having to replenish the reagents. Once the
reagents have been exhausted, or when the titration cell maximum volume
has been reached, it should simply be necessary to:-
1. DISASSEMBLE titration cell (disconnect leads from titrator)
2. EMPTY the titration cell and generator electrode
3. RINSE all parts with methanol. Do not use brush on electrodes.
4. DRY all parts
5. REASSEMBLE glassware
6. RECHARGE with fresh reagents
If the cell is heavily contaminated then it may be necessary to clean
it more thoroughly. For oil samples, cleaning with chloroform or xylene
is suggested, whilst for salt deposits a water wash may be required.
Use whichever solvent is most suited for the sample type. The titration
vessel (not the electrodes) can even be cleaned with hot soapy water
and a bottle-brush. However, after cleaning with suitable solvent, all
glassware parts, should be rinsed inside and out with methanol. They
can then be dried with a warm air blower, such as a domestic hair
dryer, placed in a low temperature oven at 40 – 50 °
C, or
left in a desiccator.
After being fully dried, reassemble the titration cell and charge with
fresh reagents.
THE MORE THOROUGHLY THAT THE TITRATION CELL IS CLEANED AND DRIED, THE
FASTER THE INSTRUMENT WILL STABILISE READY FOR OPERATION AFTER
RECHARGING REAGENTS.
Under normal conditions, the Aquamax KF should be ready for operation
within 5 – 10 minutes after reassembly, however it could take
considerably longer to completely stabilise if the drying procedure has
not been properly carried out.
What
is
maximum
oven temperature
to dry glassware?
After cleaning the glassware with suitable solvent, all glassware
parts, should be rinsed inside and out with methanol. They can then be
dried with a warm air blower, such as a domestic hair dryer, placed in
a low temperature oven at 40
– 50 ° C, or left in a
desiccator.
What
if I am “on-site” and can’t clean the
glassware, what should I do?
Although it is highly recommended that the glassware be cleaned and
dried before replacing reagents, it is not always possible to achieve
this, especially when away from the laboratory or workshop. In these
circumstances we suggest emptying the reagents into a suitable
container and re-assembling the glassware as quickly as possible. The
least time that the generator electrode is exposed to atmospheric
moisture then the faster the titration vessel will stabilise again
after replacing reagents.
Which
reagents should I use?
“Cou-Lo Formula” reagents offer optimum performance
with almost all models of coulometric Karl Fischer titrators. Our
packaging concept has been based on advice from the HSE (Health
& Safety Executive) to enable non-laboratory personnel to work
more safely.
Cou-Lo Formula “A” anode reagents is suitable for
most routine applications and is especially useful for water content
determination of oil samples.
The anode reagent, which contains the required amount of xylene and
other solubilizers, is supplied in 100ml “single
shot” bottles, no volume measurement or mixing with other
solvents is required. The cathode reagent, Formula
“C”, is supplied in “single
shot” 5ml ampoules which have “safety
snappers” pre-fitted thereby educing risk to the operator.
Each pack contains 8 x 100ml bottles of anode reagent plus 8 x 5ml
ampoules of cathode reagent plus two water standards. Weighing only 3
kilo, the total pack volume is less than one litre so they can be
shipped
as limited quantity.
How
do I change the reagents?
This is extract from the Aquamax KF user manual;
For most routine applications 100ml of Formula “A”
(anode reagent) and 5ml of Formula “C” (cathode
reagent) are used. When analysing Transformer oils, Crude oils and
other petroleum products Formula “A” is especially
suited as it contains other solvents to improve sample miscibility and
solubility.
(When analysing samples of Ketones, amines or others which may
interfere with the reaction it is advisable to use specialised reagents
which can be obtained from various suppliers).
 |
Although
reagents can be poured into the titration vessel whilst it is located
on the titrator, we recommend that the vessel and electrodes are
removed from the instrument whilst this procedure is performed to avoid
reagent spillage onto the instrument casing. (Any spillage onto the
instrument casing should be wiped off
immediately to avoid damage or staining). |
 |
Remove
the drying tube and injection septa. Using the funnel supplied, charge
the titration vessel upto the lower line with Formula
“A” reagent. For your convenience these reagents
are supplied in “single shot” bottles which contain
100ml so it is not necessary to measure any volumes – simply
pour in the complete bottle |
 |
Also
using the funnel, charge the inner chamber of the generator electrode
with Formula “C” reagent which are supplied in
“single shot” 5 ml vials which havce
“safety snappers” pre-fitted thereby reducing risk
to the operator.(It is not necessary to clean the funnel between
reagents.) |
 |
Reconnect
the drying tube and injection septa so that the titration vessel is
sealed from ingress of atmospheric moisture.
Locate the complete titration vessel
onto the titrator and connect the
electrode leads onto the appropriate sockets
|
How
often must I change
reagents?
This
depends on the type and number of samples. Average reagent change
is about once every two weeks. Talk with our experts about ways to
optimize reagent use.
Coulometers can determine the water content of multiple samples on one
single charge of reagent. The criteria governing reagent life are
threefold:
The physical size of the titration cell usually allows for 50
– 60 ml of sample to be added. Sample volumes of 0.1
– 2.0 ml are typical for most oil and petroleum products
therefore the maximum volume of 50-60 ml is not usually a limiting
factor.
The second criteria governing reagent lifetime is the total amount of
water that can be analysed before saturation. A standard charge of
100ml anode reagent can usually analyse upto 1 gram of water.
Considering that the injected sample volume is normally quite small,
and that usually the analysis is for the determination of low levels of
water, then this water capacity should not become a limiting factor
either.
Similar to all other Karl Fischer reagents, coulometric reagents
deteriorate when left out in sunlight and with increases in
temperature. Life expectancy for one charge of reagents when left in
the titration cell can be 2-3 weeks although this is also dependent on
the total amount of sample injected and the amount of water titrated.
How
do I calculate reagent
requirements and cost?
The
reagent will typically have to be replaced every two - three weeks.
A reagent change uses 100 ml of anode reagent and one vial of cathode
reagent. Divide the price of the reagent by the number of samples
analysed to determine the cost per analysis.
How
do I know when the
chemicals need to be changed?
Three
factors govern reagent life as explained in another section.
Usual indications that reagents are in need of being replaced are,
darkening of the cathode reagent, progressively higher background drift
values, slower titrations, unstable baseline as end point approached.
Are
all reagents the same?
Although
any Coulometric Karl Fischer reagent can be used with the
Aquamax KF, the Cou-lo brand is formulated to promote optimal results.
This is especially the case with oil samples due to the excellent
dissolution of sample
and reagent.
Are
reagents dangerous?
Coulometric reagents are generally classed as hazardous and / or toxic.
Each pack of Cou-Lo Formula reagents contains MSDS data sheet and
copies of these can also be downloaded from the G.R. Scientific
website.
Can
I use an oil evaporator with the Aquamax?
Some oils contain additives that can interfere with water measurements
and therefore require a secondary technique employing an evaporator.
Most commercially available evaporators can be easily interfaced with
the Aquamax KF.
Can
KF titration be used for predictive maintenance?
Water, acid and fine particulates in EHC (electrohydraulic control)
fluids are the primary causes of failures. Water is the simplest of
these to measure. Monitoring water content can provide major financial
savings in fluid replacement and equipment failure.
Is
KF titration more reliable than the “crackle test”
or distillation technique?
Both of these techniques are semi-quantitative at best and are
sensitive to only large amounts of water. The Aquamax KF is reliable
and accurate down to 1 ppm of water.
Is
the syringe that I use important?
If samples are being analysed by W/w then the accuracy of the syringe
is less important. However, if analysing by V/SG method, whereby a
measured volume of sample is injected into the titration vessel, then
the syringe and syringe technique of the operator, are of great
importance. A good quality gas tight syringe with luer lock needle is
recommended.
Why
does the needle have to go into the reagent?
For samples such as transformer /insulating oils, which are viscous and
contain low levels of moisture, we recommend inserting the syringe
needle below the surface of the anode reagent before injecting the
sample. This ensures that the sample is given enough time to disperse
in the reagent and for the detector electrode to see any signal change.
Please remember that no titration
takes place until after the detector
electrode has seen a signal change caused by the presence of water.
What
is the sample injection technique for transformer oil samples?
This is extract from the Aquamax KF user manual;
Program the Aquamax KF with parameters for the analysis. For
Transformer Oil samples, these parameters are usually:-
Result Format = mg/kg or ppm
Calculation Mode = V/SG
Sample Volume = 1.0 ml
Sample SG = 0.875
ANALYSIS METHOD
1. Confirm that Aquamax KF is in “Ready” mode
2. Flush 1.0ml syringe several times (minimum 6 times) with sample
3. Fit luer needle and flush through with sample
4. Draw sample into syringe beyond the 1.0ml marking
5. Invert syringe so that any air bubbles can be ejected through the
needle and adjust syringe plunger to the 1.0 ml mark
6. Wipe off excess sample from outside of needle using a clean, dry
tissue or paper towel
7. Pierce needle through injection septa of titration vessel (1
– 2 cm)
8. Press START
9. Push needle into anode reagent and inject sample
10. Withdraw needle from titration vessel
11. Read result, in mg/kg (ppm) water, on display and printout
12. Repeat steps 2 – 11 if duplicate result required
What
results am I looking for when using standards?
There are various commercial water standards available, including our
own Cou-Lo Formula standards. Some standards provide results as water
content by weight, others by volume. As many Aquamax KF users require
on-site operation of the titrator they do not always have a balance
available. As such we decided to provide water standards based on 0.1
milligram per millilitre and 1.0 milligram per millilitre. This means
that the operator, even when out from the laboratory, can check that
his titrator is operating correctly by simply injecting 1.0 ml of
standard which will give results
of 100 or 1000 microgram counts
Can
display show calculated ppm / % water whilst running titration?
The Aquamax KF is programmed so that the calculated amount of water
(ppm or percentage) can be displayed live during the titration. It is
not necessary to wait until the end point has been reached to see if
water content is going to be above specification.
Can
I enter sample data, e.g. weight, during titration?
The Aquamax KF is programmed so that the sample data required for the
calculation can be entered during the titration. This is particularly
useful when analysing samples by W/w calculation (Weight) as the Tare
weight can be entered whilst titration
is still in progress.
What
are delay times for? When would I use them?
The Aquamax KF has two different delay times which are operator
programmable. Start Delay enables additional time to be added before
electrolysis current is applied and the titration starts to count. This
is useful if the sample is very viscous or is slow to release water
Minimum Titration Time allows the titration to commence and to count as
normal but does not enable the end point to be reached until at least
the programmed minimum time has elapsed. This is useful when using a
vaporiser or sometimes when analysing gas samples which have very low
water content.
Can
I upgrade my unit to add new features or fix problems?
Older Aquamax KF units can be re-programmed with our latest versions of
software for very little cost. Alternatively, we can also offer
substantial trade-in discounts if your old titrator, regardless of make
or model, is given in part exchange. Contact us for details.
I
need replacement glassware for other manufacturers’ titrator
– can you help?
Our glassblowers have specialised in manufacturing coulometric Karl
Fischer electrodes, vessels, etc, for many years. We can provide
equivalent glassware for almost all makes and models of coulometric
Karl Fischer units at a very competitive price. Contact us for details
I
have a question not listed, where can I get more information?
Our specialists and consultants have spent many years on Karl Fischer
titrations – let them help you. Call us at 412-841-6988 or email us at If you have a sample analysis
problem, or if you are not sure if Karl Fischer titration would be
suitable, contact us for free technical and application advice.