The Scientific*gear Blog

This might sound a bit technical but has significant importance in the world of chemistry: validating burettes on an automatic titrator.

For those who are not familiar with burettes, they are glass tubes used in laboratories to measure the volume of liquid dispensed. They are essential in titration, a process of chemical analysis used to determine the concentration of an unknown solution by reacting it with a known solution.

An automatic titrator, on the other hand, is a device used to automate the titration process. It reduces human error, increases precision, and saves time. However, to ensure accurate results, it is crucial to validate the burettes used in the titrator.

Now, let me get personal and share a story. I once worked in a lab where we had a faulty burette that was not calibrated correctly. We did not realize it until we compared our results with another lab, and they were different. We had to redo all our tests, causing a significant delay in our research. It taught me the importance of validating instruments before conducting any experiments.

To validate a burette, we need to check its accuracy by measuring the volume of liquid it dispenses. We can use a standard solution of a known concentration to verify the accuracy and precision of the burette. This process ensures that the titration results are reliable and trustworthy.

Here's a random fact related to the topic. Did you know that the burette was invented by a French chemist named Francois Antoine Henri Descroizilles in 1824?

To sum this all up,  validating burettes on an automatic titrator is crucial to ensure accurate results in chemical analysis. It may seem like a small step, but it can make a significant difference in research and experiments. So, let's not overlook the importance of this process and always validate our instruments before conducting any tests.

P.S, Check out our Burette Validation & Repair Service. 

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In this short 30 minute webinar we dive into understanding the common titration application known as TAN or "total acid number", also known as,  ASTM D664.  As part of our titration webinar series we have a fun and uncomplicated talk about this titration application known as "total acid number".  

In this short but informative webinar we explore:

• What is TAN, total acid number, ASTM D664?
• Why do we test for it?
• How do we test for it?
• How do you set up the titration application?
• What are common problems you need to avoid?
• Best practices you should know about and try to follow

It only takes a few seconds to register for this highly interactive webinar (recorded).  You will be able to watch, send us emails with questions, download various application resources including the application notes, electrode prep tips, and more.

This is a valuable tool for seasoned experts and first timers.

 

                               

 

 

We get this question a lot.  So, we decided to try and figure it out the best we can.  In this analysis, we are only going to examine and include the per-unit cost of the titrator (automatic) and the reagents (silver nitrate - AgNO3).  It seems we could include other factors including human resources and electrical power requirements but these can vary greatly so we will leave them out of this analysis.  Additional ancillary costs can always be added later.

Let's start off by assuming we purchase a basic automatic titrator for $8,500.00  

Next, let's examine our most required consumable.  Silver Nitrate- AgNO3.

To do this we need to assume a sample with a given amount of sodium.  Sodium is generally expressed in mg on food labels. 

 

We performed a salt titration on this food product (soy sauce).  On the label, we can see that the amount of sodium is 590mg of sodium per serving.  For this titration (see below), you can see we used 15.8ml of silver nitrate @ (0.1N mol).   

Note that silver nitrate can come in different strengths so there is a little math we need to consider when deciding on which strength of silver nitrate we should use.

Let's consider using a different strength silver nitrate.  Let's look at using 0.5N mol instead of the 0.1N mol we used in our test.  Initially, we used 0.1N for our titration.  So dividing 15.8mL by 5 helps us see that using a bit stronger silver nitrate will reduce our consumption of silver nitrate.  In this case,  around 3mL per test.   But it's not that simple.  Conversely, we can change the strength of the silver nitrate and make it stronger as long as you don't have other samples that have a lot less sodium.  Otherwise, it would be too strong for the other samples with less sodium and it would not be ideal in those situations (You probably would not find the endpoint).  Bottom line, if you are working with only one burette (doses the silver nitrate), then you are going to need to pick a silver nitrate strength that can be used for all of your samples.  The only alternative would be to refill the burette each time with different strength silver nitrate, or, have a swappable burette on hand.  Having a swappable burette means you can have preloaded burettes with different strength silver nitrate and you can then easily swap them on and off the titrator when needed.  Even better, some titrators can be configured to have two or more onboard burettes which would alleviate the need for manually swapping burettes. 

Let's ignore this for the moment and continue to focus on our cost analysis assuming a single burette.

To give you an idea about pricing for silver nitrate. 

•  We recently purchased some 0.1N mol Silver Nitrate (strength).  A 1 Liter bottle cost approximately $75.00.  Divide $75.00 by 1,000 and the per mL cost is $0.075 per mL of 0.1N mol silver nitrate.   Assume 15.8mL of 0.1N mol silver nitrate per test => 15.8x$0.075=$1.19 per test.

• Assume 0.5N mol Silver Nitrate (strength). => 15.8mL divided by 5 = 3.2mL of silver nitrate per test. (e.g. you will use less with stronger).  Some recent pricing for 0.5N mol; $170.00 / 500mL => $0.34 per mL, or Bulk pricing if you buy a larger bottle $1,000.00 / 4L (4,000mL) => $0.25 per mL ~ 3.2mL per test x $0.34 per mL = $1.09 per test or 3.2mL x $.25 per mL = $0.80 per test.

So if you can purchase silver nitrate in bulk you can drive down your per test cost.

When you decide to test for salt (NaCl) using a titrator you are going to have that initial outlay to pay for the titrator.  After that, it's really a question of what strength of silver nitrate you are using and the amount you are using.   Hopefully, from this example, you can see how the price per test can range from about $0.80 per test to almost $1.20 per test.  So if we do some estimating you could say on average it costs about $1.00 per test.  If you are testing 200 samples per day your daily cost for silver nitrate will cost you about $200.00.

Now let's assume depreciation of the titrator using the straight-line method with the useful life of the titrator equal to 5 years (I think this is what a tax accountant would assume for tax purposes).  $8,500 / 5 = $1,700.00 per year.  Let's assume 251 working days per year ==> $1,700 / 251 = $6.73 per working day in depreciation expense.  In this case, divide that by 200 tests today, and that = $0.03 per test.  

I think these numbers (for the most part) provide a good working basis for determining daily operating costs.  They're probably not perfect but they show you how to go about figuring this out. As always we hope you find this information helpful!

 

 

 

 

 

This article is not intended to explain a manual titration process but rather how you can configure an automatic titration system to run both acid and salt titrations independently and or as a combined method.

Performing acid and salt titrations is a popular requirement in the food industry.  Some foods like tomatoes for example tend to have naturally occurring acidic properties but also take on a salt component when processed into other intermediary products like pizza sauce or spaghetti sauce.  

Although sodium (Na) is an important element to measure and report on food labels, salt (NaCl) content is also important in measuring to ensure the taste is good and repeatable during the production process.

Performing titrations whether manually or with the use of an automatic titrator involves a burette where specific amounts of titrant are delivered to evaluate the potential and or content of what is being measured. Results are usually reported in % for both acidity and salt content.

Here is an example of how you might set up a titration for testing both acidity and salt.  Below we have 2 scenarios.  The first scenario is configured so that the titration for both acidity and salt can be performed using a single sample.  To accomplish this you will need 3 burettes.  We will first perform the acidity titration using burette #1 with NaOH (Sodium Hydroxide) as our titrant.  In our example, during the acidity titration, the pH will rise to about 8.2.  At the end of the acidity titration, the pH level will be too high for us to run the salt titration so we will need to lower the pH.  We accomplish this task by dosing HNO3 (Nitric Acid) into the sample using the burette on the Automatic Piston Burette (APB ~ we will call this burette #3).  We will dose HNO3 to reduce the pH down to about 4.1.  Once the pH level is reduced the salt titration can begin.  The second burette (burette #2) located on the titrator then performs the salt titration using silver nitrate (AgNO3) as the titrant.  It is worth noting that silver nitrate comes in various strengths and so depending on your sample and the amount of "salt" you expect to find, you may need to adjust the strength (1.0N vs. 0.5N vs 0.1N, etc).

What the setup will look like

Electrodes we will use:

• pH glass electrode (noted as H171 in the diagram)
• combined silver electrode (noted as C373 in the diagram)

When running the titration using only one sample to obtain both the acidity % and the salt %, we will use both electrodes as the combined silver electrode will act as a reference electrode for the pH electrode. 

When running a single titration on two different samples in two different beakers, leave both electrodes and nozzles in the samples ensuring to clean the nozzles and electrodes between tests of each sample.  In this scenario, the combined silver electrode (C373) will also work as a reference electrode for the pH electrode (H171) while running the acidity titration.

Summary of key consumable:

• Silver Nitrate (AgNO3) titrant for salt titrations
• Sodium Hydroxide (NaOH) titrant for acidity titrations
• Nitric Acid (HNO3) buffer if combining methods
• Combined Silver Electrode (C373) for salt titrations
• pH glass electrode (H171) for acidity titrations

In the video below we show the titration setup described above.

 

We hope you find this information useful!

                                                   

 

 

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Hello!  Please meet our new Web Helpers!  Moisture Elle, Karl Fischer, Shaker Sam, Terri Tenso, and Vivian Visco!  Each of our helpers will provide technical information ranging from general topics to more in-depth discussion pertaining to; Moisture testing, Karl Fischer Titration, Particle Size Analysis, Surface Tension, and Viscosity.

 

 

Sometimes pressing a button and hearing a beep just drives you crazy.  We know.  Below we received some video of a problem where the operator could not move the piston burette up or down on their automatic titrator.  We decided to replicate the problem and then show how to take corrective action.  We hope you find the video informative even though it is raw footage.  Send us your questions too.  Video, audio, pictures, etc.  We can use any format.

 

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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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