Top 10 Tips for Titrating

Achieving Speed and Accuracy in your Lab with Automated Titrators

Use the Thermo Scientific™ Orion Star T900 Series All-in-One Titrator for flexible pH, redox, and ion concentration titrations. Here's a list of the Top 10 Tips from Thermo Scientific™ for Titrating.

Choose an Autotitrator

Convert from manual titrations to an autotitrator to get the benefits of improved accuracy and precision, safe handling of corrosive titrants, ease-of-use, better use of technician time, automated calculations, and automatic data logging. If you are currently outsourcing your titrations, use an autotitrator to run your samples in-house. This can save time and money and provide a quick turnaround for faster results.
Pre-Program to Save Time

Converting to an automatic titration is often a simple one-time task, resulting in a saved programmed method that can be copied, shared, and used for all future titrations. To convert a manual method, use a preprogrammed method that is already available for the titrator, or enter the parameters of the manual method directly into the titrator. Either process typically takes only a few minutes to complete.
Standardize Your Titrant

Over time, standard titrant solutions age and can change concentration. For higher accuracy, determine the exact concentration by standardizing the titrant regularly. It is common to standardize your titrant on a weekly basis, but other standardization frequencies may be suitable, depending on the desired accuracy of the results and the stability of the titrant.
Choose the Right pH Electrode

The best pH electrodes respond quickly to large and small pH changes, are stable, and accurate. A fast and accurate pH electrode leads to fast and accurate pH titrations, so choosing the right one is important. For example, ASTM has written standards for acid number and base number titrations that recommend the type of pH electrodes to be used and the test procedures to verify electrode performance. The pH electrodes that we recommend in our non-aqueous pH titration application notes (for acid number and base number) meet the recommendations and performance tests of the ASTM standards.
Calibrate pH for Best Accuracy

In most cases, it is recommended that you calibrate your pH electrode once a day when titrating acid/base samples. If in doubt about the stability of the calibration over the course of the day, read a pH buffer standard (in measure mode) that is close to the endpoint pH. If the buffer reads close to the accepted value at the measured temperature, your calibration is still good. In some cases, for example, if the titration technique is “equivalence point” (rather than preset endpoint) and the measurement units chosen are mV units (rather than pH units), calibration is not necessary for accurate titration results. However, calibration still gives valuable information about the performance of the electrode and can indicate the need for maintenance or replacement.
Measure Temperature

Using an automatic temperature compensation (ATC) Probe or Triode to measure temperature provides valuable temperature information that is needed for an accurate pH calibration and for adjusting the pH calibration slope when the temperature changes. This is very important for the accuracy and precision of a pH titration that uses the preset endpoint titration technique.
Titrate Faster and Run More Samples

When speed and sample throughput are important, there are different options for maximizing your titration. One option is to make use of the pre-dose parameter. If your titration typically takes a known amount of titrant, program a pre-dose into your method to dose most of the titrant in one shot. For example, if a titration typically takes about 8 mL, you might choose a 7 mL pre-dose. The titrator will only have to search for the endpoint in the last mL or so. Another option is to choose a different titration process control parameter. For example, if the control is “routine” try changing to “quick” to speed up the titration. Another option is to titrate less sample. If a 10 mL sample takes 10 mL of titrant, try using 2 mL of sample, which will take only 2 mL of the titrant. When using an auto-titrator, 2 mL can be added in 0.001 mL increments. That allows plenty of precision, even though only a small amount of titrant is used.
Care For Your Electrodes

Good electrodes require some routine care, just like a car. Flush and refill the filling solution regularly— weekly or biweekly is usually effective. Store the electrode in the recommended storage solution and change the storage solution biweekly. Depending on the type of samples analyzed, periodic cleaning may improve the performance of the electrode. Follow the recommendations in our application notes or the pH electrode user guide.
Choose the Best Endpoint Technique

The auto-titrator can find the pH endpoint in one of two ways: 1) by going to a preset pH value that we specify (e.g., pH 8.3) or 2) by finding the endpoint based on a mathematical evaluation of the titration curve. These techniques are the preset endpoint and equivalence point techniques, respectively. When choosing your endpoint technique, follow the recommendation from the core method application note that is the same or like your titration. If your titration is different, follow your current manual titration method. For example, if you are currently doing a manual titration with a pH electrode to a pH of 8.3, you would choose the preset endpoint titration technique and specify pH 8.3. If you are currently doing a manual titration of a strong acid/strong base or titrating to a color endpoint, you might choose the equivalence point titration technique and let the titrator determine the location of the endpoint. (Note: These are general guidelines. Some titrations differ. If in doubt, contact your local sales specialist or our technical service team).
Preserve the Integrity of Your Titrant

To preserve the integrity of your titrant, use the recommended titrant bottles, caps, and tubing, which are designed to minimize evaporation and prevent particles from getting into the titrant. Some titrants, such as sodium hydroxide titrants for certain titrations, can be protected from carbon dioxide absorption. Place a carbon dioxide sorbent (scrubber) tube on the titrant cap air intake. Other titrants, such as iodine/iodide or silver nitrate, should be protected from light by the use of opaque or brown glass titrant bottles.