Electrode Shower Cleaning for Auto Titrator Sample Changers

By Hank Levi on Thu, Feb 25, 2016 @ 12:04 PM


ELECTRODE RINSE WITH SHOWER ACCESSORY:

Sample changers that are connected with automatic titrators generally are there for a reason.  Efficiency. From an operators point of view getting multiple tests done quickly while being able to take on other tasks in the lab is a key productivity booster.  Sample changers offer various sizes ranging from as few as 6 positions for samples up to some of the largest exceeding 50 sample positions.  Sample changers either have rotating carousels or an arm that moves electrodes and nozzles from sample to sample.  Each time a sample test is completed the electrode must be cleaned before moving on to the next test.  Many sample changers offer as standard a dip rinse between sample testing and as the name suggests it's really nothing more then dipping the electrode in clean water or solution.  For some samples this process is sufficent but for others it is not enough to effectively clean the electrode before the next test.  Luckily most manufacturers of sample changers offer additional cleaning power with the use of a shower rinse system.   Below is a video showing how a shower rinse process works.   Water is stored in a container and then is flushd and rinsed in one of the sample positions designated as the cleaning station.  Water is evacuated via tubes to a drain or sink.  


 
 
 
 
 
 
 
 

 

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Automatic Titrator with Mini Sample Changer Video

By Hank Levi on Tue, Nov 20, 2012 @ 11:11 AM

AT-700 Automatic Titrator

The AT-700 automatic titrator provides operators a variety of choices including the use of an Mini Sample Changer CHA-700integrated mini sample changer.  The mini sample changer can hold up to 6 samples.  The design utilizes a rotating arm that holds the electrode(s), dispensing nozzle(s), and propeller stirrer above each sample and maneuvers from sample to sample.  The compact design allows a small footprint on the bench because the titrator sits on top of the sample changer.  Watch the short demo video to learn more about this titration system.

 

        Get more information here 

 

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Automatic Titrator AT-700

By Hank Levi on Mon, Nov 05, 2012 @ 02:31 PM

Automatic Titrator AT-700

The AT-700 automatic titrator is a new compact potentiometric titrator.  The unit is ideal for conducting basic end-point titrations all the way up to more complex configurations that can include a sample changer, an additional permanent burette, to a chain of 8 automatic piston burettes (APBs).  The titrator can work stand alone or pair with advanced computer controlled software. 

Watch the video to learn and see more.

 

 

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Titration: Bromine number vs. Bromine Index

By Hank Levi on Mon, Aug 27, 2012 @ 12:09 PM

BROMINE TITLEDon’t know whether you need to run a Bromine Number or Bromine Index?  Not sure what the difference is between Electrometric or Coulometric?  And just how many approved ASTM methods are there, anyway? 

Well, a good place to start is to check out the comparison table below and evaluate your sample(s) with respect to the scope & limits of products listed for each method.

If you’re trying to decide which of the last two Bromine Index methods to use, remember that the D1492 Coulometric method is most often employed for materials having very low expected values ( > ~20).

Be careful about converting back and forth between the two using that factor of 1000.  You can safely convert a Bromine Index to a Bromine Number by dividing it by 1000, but it’s not OK to derive a Bromine Index from a Bromine Number by multiplying the Number by 1000.

                                         DOWNLOAD A COPY

 


 

Interested in getting more detailed information on how to do Bromine using your Karl Fischer titrator? 

              Get the complete Karl Fischer method here

  Bromine Chart

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Karl Fischer Over Titration and 7 things you should know about it

By Hank Levi on Wed, May 02, 2012 @ 06:30 PM

We have all seen it.  We’re running a test to see how much moisture is in our sample when inexplicably the liquid inside the Karl Fischer vessel starts to turn from a normal light-yellow color to a dark burnt-red looking color.  Sometimes the titrator screen will inform us of the problem with a digital readout stating the dreaded

OVER-TITRATION!” 

kfbeforestart resized 600describe the imagedescribe the imagedescribe the image

 

Sometimes the digital readout says nothing at all.  In either case the operator knows something has gone wrong because the Karl Fischer Titrator is no longer giving moisture results.  A panic to figure out the problem and get testing underway again becomes the immediate priority. 

But where do you start?  

As it turns out “over-titration” is probably one of the top 2 or 3 complaints or issues we hear about from operators.    So what is causing this problem to occur?  How can we determine the source of this problem, fix it, and more importantly how can we avoid it?

 
This is a critical question for operators and managers working in a production or QC environment who are concerned with keeping their Karl Fischer Titrator 100% “in-service”, day-in and day-out.   Having the ability to identify the problem correctly so appropriate measures can be taken quickly is very important.

 
So how do we approach the problem of “over-titration”?   By knowing the facts.  Having a clear understanding of the process can help operators correct the problem faster when time is of the essence.  

Important facts you should know about over-titration:  
  1. Over-titration is a state where there is more iodine present in the vessel than water (general definition).
  2. When over-titration occurs the vessel will become very dark as a result of the abundance of iodine present inside the vessel.
  3. The reagent inside the vessel should normally have a light-yellow color absent a very dark sample such as oil.
  4. The Karl Fischer Titrator always attempts to maintain an equilibrium where only enough iodine is introduced to counter and neutralize the water present inside the vessel.
  5. During a single titration test there should only be enough iodine introduced to counter and neutralize the amount of water present inside the titration vessel during that test – no more, no less.
  6. Any incident that interferes with the final amount of iodine introduced during the titration test can lead to dis-equilibrium and result in more iodine being introduced than necessary.
    Important facts you should know about Karl Fischer Titrator Glassware:  
  1. The Karl Fischer Vessel and Glassware is composed of the following
    1. Vessel (coulometric and volumetric)
    2. Generator Electrode (coulometric only) - The Generator Electrode is a precision electrode designed to deliver an electrical current inside the vessel to the reagent – causing the reagent to produce iodine
    3. Titration nozzle (volumetric only) - The titration nozzle delivers precise amounts of iodine (composite or titrant) via a burette driven mechanism using a piston
    4. Detector Electrode (coulometric and volumetric) - The detector electrode has a sole purpose and probably the most important role in continuously monitoring and determining the conductivity levels within the titration vessel.
  So what are the causes that can lead to over-titration? 

✓ A damaged Detector Electrode

✓ A "Tricked" or "Fooled" Detector Electrode (no joke)

 

Since coulometric and volumetric Karl Fischer Titrators handle the delivery of iodine differently it’s worth describing the two methods separately.  

A Word About Coulometric Karl Fischer Titration:

In a coulometric system the reagent is a complete system where it is designed to release iodine when the generator electrode delivers an electrical current to it.  So what causes the generator electrode to deliver too much current causing the over production of iodine?  Another way to say it is, “who or what” is telling the generator electrode to continue to generate a current when it’s not needed?  

   
The detector electrode!  So why would the detector electrode do this?   describe the image
Without getting into too much of the electronics the detector electrode is designed to “detect” conductivity in the vessel.  Depending on the amount of conductivity detected the detector electrode will send a message to the titrator telling it to continue producing a current - enough to release the appropriate amount of iodine to counter and neutralize the water present in the vessel.  As long as this process is working during a titration an eventual endpoint will be found and a result will be produced.  


So it’s really a problem of misinformation. If the Karl Fischer Titrator is not getting the right information from the detector electrode then over-titration is possible. 

The problems we see that can effect the proper functioning of the detector electrode include:  
  1. The electrode cable.  If the cable becomes cracked or breaks it can cause a situation where the message to the titrator is to continue producing a current – continually.  In this case the vessel will become very dark and in most cases the titrator will not even know it is in an over-titration state.  The generator electrode will simply continue to produce a current, turning the vessel very dark.  There will be no other warning or notice from the titrator for the operator to see.
  2. Cracked electrode.  Sometimes mishandling or even a stirrer bar bouncing around inside the vessel can cause a tiny crack near the bottom of the detector electrode that cannot be seen with the naked eye.  These cracks can allow small amounts of reagent inside the electrode enough where errors in detection will begin to occur.  What ensues is an unstable drift that jumps around giving the titrator a misreading. The jumping around and unstable drift may be picked up by the titrator and an error stating “OVER TITRATION” may be seen on the screen of the titrator.
  3. Cable connectors.  Sometimes the connectors on the titrator itself can become dirty, wet and corroded.  Also, some electrodes use multi-plug designs that can also become dirty, wet and corroded.   These connectors if not clean and dry can lead to a similar misreading similar to a cracked electrode where the drift begins to jump around and become unstable.  The titrator may also state that there is “OVER TITRATION” when this occurs.
A "Tricked" or "Fooled" Detector Electrode you say?describe the image

If it’s determined that the problem is not the detector electrode then we need to look at the stirring action inside the vessel.  If the iodine being released is not mixing well because the stirrer is off or set too low, then the detector electrode will not realize there is iodine already released inside the vessel.  This will cause the detector electrode to continue telling the titrator to produce more current via the generator electrode up to the point where the detector electrode senses a reduction in the conductivity level inside the vessel.  Conductivity only reduces as the iodine interacts with the water.  So it is important for the detector electrode to sense the true and most accurate “mix or state” of iodine and water during the titration process.  If it does not know the true state of the mix it will be fooled into telling the titrator to keep going – causing OVER TITRATION.        

A Word About Volumetric Karl Fischer Titration:

   
describe the imageIn a volumetric system the reagent setup is different where a composite or titrant is introduced via a burette piston through a titration nozzle.  The amount of composite or titrant delivered is based upon the commands of the titrator.  The command from the titrator to the burette and piston that push out the “iodine” through the titration nozzle is, yes, given by the detector electrode.  For the purposes of this discussion the difference between the coulometric and volumetric setup is that the delivery of iodine is different.   But the same problem can occur where the iodine does not mix well and therefore trick the detector electrode in to thinking there is not enough iodine present inside the vessel to counter and neutralize the water.  Since both coulometric and volumetric Karl Fischer Titrators use detector electrodes the problems mentioned earlier about the detector electrode will hold true with volumetric titrators also.  

 

 

  7 Thoughts (DOs and DON'Ts) on Problem Solving and Prevention:  

1.  Don’t abuse the detector electrode!  Be very careful with the detector electrode and do not handle it unnecessarily.  Small bumps (clanks) here and there can lead to a crack.   Do you really need to remove the detector thinking dragonelectrode from the vessel all the time?
2.  Don’t turn up the titrator’s stirrer speed to high.  This will only cause the stirrer bar to bounce around uncontrollably and possibly hit and damage the detector electrode (crack).
3.  Do inspect all connections and connectors on the detector electrode cable and Karl Fischer Titrator to ensure they are dry and clean.
4.  Do be careful with the detector electrode cable.  Try not to bend it unnecessarily.
5.  Do make sure there is enough stirring action inside the vessel to mix the iodine around effectively.  A small vortex should be visible.  But not too fast to cause the stir bar to bounce around.
6.  Do introduce some moisture - Sometimes when you are in an over-titration situation and the vessel is already very dark you can introduce a little moisture to bring the vessel back to equilibrium.  This sometimes works and immediately the vessel turns from a dark burnt-red color to a light-yellow.
7.  Do have a spare detector electrode on hand.  This little electrode seems to get over looked but plays a huge role inside the Karl Fischer Titrator vessel.

Created on 05/02/12 at 18:10:44

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How to use a titrator to measure % sodium chloride in food products

By Hank Levi on Sun, Dec 18, 2011 @ 03:57 PM

Automatic Titrator

Titration

So you need to measure the amount of sodium chloride in your food products. While we have written about this topic previously in other posts and addressed some of the approaches used to test for % sodium chloride (including the use of hand-held salt meters) we have found that it is a more common practice to use an automatic titrator to accomplish this task.  In fact we think it is the preferred instrument and method of choice.  To be sure there are pros and cons to using different methods but we still find that titration is accepted as the primary method for getting the most accurate results.

 

How it's used

Although salt meters using the conductive method are faster (3 seconds vs. 2 to 3 mintues) and can be employed quickly in a production line process, titrators can also be implemented in the same testing environment with modest effort.  Additionally and regardless of how the tests were performed on the production line, titrators are generally put to work in the Quality Control/Quality Assurance Lab as a final check against periodic production line testing.

Supporting the use of titration as an accepted method includes some well known documented techniques including Mohr's and Volhard's methods making titration a recognized and trusted approach.

 

What's next...

Once you have made the decsion to use titration as the testing method it's just a matter of knowing:

  • What items you need

  • How to prep your sample

  • How to setup the titrator

Luckily we have already thought about this and put together a list of 8 items your going to need.  We also created an application-note providing step-by-step instructions for you to follow to conduct a titration.

                                 

                                         Created on 12/18/11 at 12:16:27  

 

                                           Created on 12/18/11 at 13:00:41

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How to test for Salt during food production

By Hank Levi on Mon, Oct 31, 2011 @ 12:53 PM

SaltMany companies produce the foods we eat.  Do you ever wonder why or how they test for salt during the production process?

Examples by Manufacturing Type

Frozen Vegetable Processor

The salt content of the blanching water is important for maintaining the bright colors of vegetables

A Condiment Manufacturer

Testing Sauces and dressings

A Cheese Maker

Measure the salinity of saltwater that the cheese is soaked in

A Potato Chips Manufacturer

Checking for salt sprinkled on fried potato slices

A fresh Cut Fruit Processor

Use a 2% saline solution with a small amount of ascorbic acid to prevent discoloration of fruits

A Deli Food Supplier

Measure foods with a salt meter vs. by taste

A Canned Food Manufacturing Plant

Measure the brine for canned tuna

A Pickles Manufacturer

Measure the salinity of the brine for salt-packed products

A Cold Cut Meat Manufacturer

Measure salt concentration of ham and deli slices

A Baker

Measure and monitor the salinity of bread dough to around 1%-2%

 

 

 

Salt which is made up of 40% sodium and 60% Chloride is an important ingredient found in food.  While salt can make food taste better, control color, and maintain food texture, it is also considered a health-risk factor (mostly due to the sodium).  Measuring and controlling the levels of salt between the extremes is a constant battle.  Producers of processed foods generally have the biggest need for identifying and controlling salt levels to address not only the taste, color, and texture of foods but also to address some of the healthier eating lifestyles more and more consumers are demanding.

For these reasons it is paramount that salt is measured accurately.  So how do we do that?

Food comes in a variety of forms.  Solid, Liquids, pastes, creams, pieces, chunks, wafers, crackers, gooey, sauces, liquids with chunks in them...let's see what else..Anyway, you get the idea.  There are a lot of ways food can be produced and consumed!

So what device or devices can we use to measure the salt found in these numerous forms of processed foods?

Well, there are a number of "salt meters" out there that can measure salt.  However, not all salt meters can measure the particular salt you are looking for in the same way.  In fact some "salt meters" can only measure salt under certain conditions and or in certain substances like water or sea water.  For this reason it is important to first consider what your going to be testing.  For example, If your food sample includes "food stuff particles" that you can grind into a paste form, then you can probably use a salt meter that utilizes the conductivity method.  On the other hand if you have a brine that you immerse food into and your only concerned with the liquid then perhaps a different salt meter will work.  

The point is this.  The form of the food at the instant you are going to perform the test is key.  Many types of foods can be formed into pastes and diluted with water.  If the food you need to test is like this then a simple salt meter utilizing the conductivity method may be able to perform the test to your satisfaction.  I say may because % salt levels and other accuracy factors may require that you use an entirely different method of titration known as silver nitrate titration instead.

Salt Meter vs. Titration?

describe the image               Titrator

A brief explanation and description of the two measurement approaches:

The Mohr method, also known as a silver nitrate titration method, utilizes the characteristics of silver nitrate that reacts with chloride ions to measure the salinity %. 

Created on 10/31/11 at 10:37:41

Conversley, some of the more popular salt meters emloy the electric conductivity method.  Both methods measure the salinity but operate on different measurement principles.  However, by creating a conversion table between the two testing methods, correlation between the set of results can be seen.

Created on 10/31/11 at 10:41:32  

Aside from the measurement capabilities of each approach there are pros and cons to each.

 
 Pro's and Con's

 

Salt Meter

Titration

 Measurement Range

Less..maybe

More

 Accuracy

Less

 More

 Ease of Use

More

 Less

 Time to test

Less

 More

 Cost

 Less

 More

 

 

 

 

 

 

 

 

 

 

 

 

 

While each method has benefits we have recently found through some informal surveying that some food processors are choosing to use both methods.  These companies are finding that it is easier to use the hand held devices and perform quick spot checks on the production line.  If any problems are identified on the production line then further verification and testing can be performed using the titration approach.  Some think using this collaborative approach is ideal.smiley2

 

ALSO READ OUR MOST RECENT UPDATES TO THIS BLOG POST : Salt related posts

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I'm Having Problems with my Volumetric Karl Fischer Titrator

By Hank Levi on Fri, Jul 29, 2011 @ 11:55 AM

Most operators who measure moisture Volumetric Karl Fischer Titratorusing a Volumetric Karl Fischer Titrator tend to have difficulty in 3 areas.   Unlike Coulometric Karl Fischer Titrators where the equipment setup and reagents are fairly straight forward, Volumetric Karl Fischer Titrators differ greatly.  Understanding how a Volumetric Karl Fischer Titrator differs and how the equipment functions is not only paramount in terms of knowing how to operate the instrument it is critical if you want to obtain accurate and repeatable results.

8 out of 10 questions we receive usually fall into one of these 3 problem areas:

 

  1. What REAGENTS should I use for testing my samples?  Titrants, Composites, Solvents?

  2. "TITER VALUE" ..Who, What, Where, Why and How?

  3. "SAMPLE SIZE" ..How much do I need or should I use? 

Although these 3 areas at first may seem problematic and unrelated they are not.  In this 9-minute presentation we will explain why the burette size matters, how to calculate a correct sample size and explain how the volumetric titrator reagent strengths work.  Tying all three areas together will hopefully not only clear up some of the mysteries surrounding Volumetric Karl Fischer Titration but also empower operators with choices for conducting tests under varied conditions.  And, oh yes, obtain accurate and repeatable results every time. 

Created on 07/29/11 at 11:54:29

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Karl Fischer Titration and Water Standard Presentation

By Hank Levi on Tue, Jun 28, 2011 @ 10:43 AM

Kf waterstandard presentation resized 600In this presentation we discuss the basic Karl Fischer Water Standards and talk about some of their uses for both Coulometric and Volumetric Karl Fischer Titration.  We also describe some of the related problems that can be identified and overcome by using Karl Fischer Water Standards.

  • Karl Fischer Water Standards
  • Why we use them
  • Coulometric Karl Fischer
  • Volumetric Karl Fischer
 

Created on 06/28/11 at 10:48:28
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Karl Fisher Titration and drift

By Hank Levi on Fri, Jun 03, 2011 @ 12:36 PM

karl fisher driftSimply put, drift is background moisture that the Karl Fisher titrator is detecting.  What is background moisture?  Well, it is moisture that the Karl Fisher titrator (specifically the detector electrode) is detecting inside the vessel -that’s not coming from your sample.  Drift or "background moisture" can be the result of having the titration vessel sitting idle for some time where moisture has slowly infiltrated and accumulated inside the vessel, or it may be the result of a leak that is allowing a small amount of moisture to enter the vessel continually.  Although we might like to think that the Karl Fisher titrator vessel is air-tight/moisture-tight, it is not.  Depending on how well the vessel is sealed there may be a little or there may be a lot of background moisture interference.  All Karl Fisher titrators deal with the drift issue.  Unfortunately drift cannot be completely eliminated but the good news is that it can be reduced, measured, isolated, and discarded from your test results.
Before a single test is run on a Karl Fisher titrator it must go into a “ready” mode.   But before the titrator can go into a “ready” mode it most likely will go through a “pre-titration” mode.  During the “pre-titration” mode excess drift (moisture) is detected and removed by the reagent inside the vessel.  A “ready” mode ideally will occur when the drift being measured is low and steady/stable – usually below .1 micro grams per second.  Once the drift becomes low and stable the Karl Fisher Titrator records the drift level and goes into a “ready” mode and will allow the operator to introduce a sample into the vessel.  Upon completion of the test the Karl Fisher titrator adds up all of the moisture detected over the duration of the test and subtracts out the known drift level that was also measured during the test.  This process of knowing what the drift was before the test allows the Karl Fisher Titrator to then determine and backout the drift -leaving only the moisture detected from the sample as your result.

 

Created on 06/03/11 at 12:38:02

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