Manual titration is a common analysis method in many labs. However, it has several drawbacks – subjective endpoint detection, risk for manual errors, or lack of data integrity.
In this article, we will show you what aspects you should consider when converting your manual titration to an automatic titration.
Disadvantages of manual titration
Manual titration involves adding titrant dropwise from a buret to a sample solution. Endpoint detection is typically done visually (by eye) using color indicators. This analytical method remains widely used because it requires only a glass buret and a flask. However, it comes with several notable disadvantages:
Subjective endpoint detection: Visual recognition of the color change depends on individual perception.
Drop size accuracy: The precision of the analysis is influenced by the size of each drop.
Time-consuming process: Manual titration takes considerable time. This includes not only the titration itself, but also cleaning and refilling the buret and manually calculating the results.
Data integrity risks: When performing manual titrations, results are often recorded by hand, transferred to spreadsheets, and then manually entered into a LIMS. Each step introduces potential for human error and requires thorough quality control checks.
Using an automatic titrator (autotitrator) helps operators to overcome these limitations.
What is autotitration?
Autotitration refers to the automation of one or more steps in the titration process. There are three levels of automation, depending on the setup:
Partial automation: Only a single step is automated. For example, an electrode is used for objective endpoint recognition, or the titrant is added manually using a more precise dosing device.
Stand-alone automation: A titrator performs the entire titration, including titrant addition, endpoint detection, and result calculation. The operator is still responsible for preparing the sample and cleaning the equipment afterwards. Figure 1 below shows a stand-alone titrator.
Fully automated titration: The titrator is combined with an autosampler, allowing full automation of the titration including sample preparation and equipment cleaning. This setup enables the operator to focus on other tasks and significantly reduces human error.
Fig. 1: Stand-alone automatic titrator with piston buret (1), titration stand with integrated stirrer (2), electrode (3) for endpoint detection, and display (4) for control and results.
Metrohm offers several titrator families with different capabilities to match specific user requirements. Use the guide on our website to get the best match for your needs:
How do I transfer manual titration to autotitration?
We recommend a six-step process to transfer a manual method to an automatic one:
Fig. 2: Steps to transfer a manual titration to an automated one.
Select a titrator based on requirements regarding compliance, instrument control, sample throughput, and reaction type.
Choose a sensor suitable for the titration reaction, sample matrix, and sample volume.
Adjust the sample size so that the equivalence point lies between 10% and 90% of the buret volume. If necessary, modify the diluent volume to ensure that the sensor is fully immersed.
Select the titration mode based on the titration reaction. Dynamic mode is recommended for fast titrations. Monotonic mode is better suited for slower titrations where the equivalence point is reached abruptly.
Optimize the titration by placing the electrode upstream of the buret tip, selecting a stirring speed that does not lead to vortex formation, and defining start and stop volumes.
Validate the method to ensure reproducibility and reliability.
Get more details on this process
The full version of this article takes you through each of these steps in detail. Check it out now:
