2024年4月22日
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Titration is one of the oldest analytical methods and finds its use in various industries. For instance, it is used to analyze drinking water or determine the metal content in battery materials. This blog post covers the principle of titration, its process, and presents the different titration types.
To read about a specific topic, use the navigation below.
Titrations are used to determine the concentration of an analyte in a sample solution. For this, a standard solution of a known concentration, called titrant, is added to the sample. Titrant and analyte react in a stoichiometric manner. The analyte concentration is calculated using the amount of titrant, its concentration, and the sample size. Table 1 lists some common titration terms.
Term |
Definition |
Analyte |
The substance of interest for which the amount needs to be determined. |
Endpoint |
The point at which the titration is complete. A color change or another indicator (e.g., pH value) signals the endpoint. It should be as close as possible to the equivalence point. |
Equivalence point |
The volume at which the reaction between titrant and analyte is finished. |
Indicator |
A substance used to indicate the endpoint of a titration. Historically, these are color indicators. Today, electrodes or other sensors have replaced color indicators. |
Primary standard |
A primary standard is a certified, highly pure, and stable substance. It is used to determine the exact concentration of the titrant. |
Standardization |
The process to determine the exact concentration of the titrant. Learn more about this process in the blog post «What to consider when standardizing titrant». |
Standard solution |
Another term used for titrant. |
Titrant |
A solution with known concentration used to determine the concentration of the analyte. |
Titration curve |
The curve obtained when plotting the used titrant volume against the signal of an electrode or sensor. |
Titration equation |
Formula used to calculate the concentration of the analyte. The equation depends on sample type (liquid or solid), stoichiometry, and the desired unit of the result. |
First, the titrant needs to be standardized. This step provides the exact concentration of the titrant solution and increases the accuracy of the result. Learn more about this process in the blog post «What to consider when standardizing titrant».
For the titration, samples must be in solution. Therefore, solid samples are dissolved or pretreated to release the analyte (e.g., by digestion, extraction, or ashing).
Sometimes auxiliary solutions need to be added. For example, redox titrations often need to be carried out at a specific pH value. Indirect titrations always need an auxiliary solution, as the analyte must be converted into a reactive form. This reactive form will then be titrated.
For back-titrations (or residual titrations), an excess of a reagent is added first. This reagent reacts with the analyte and its excess is then titrated. Read the blog post «What to consider during back-titration» to learn more about this kind of titration.
During the titration, it is important to stir the sample. This ensures that titrant and analyte are mixed well. Titrant is added to the sample until the endpoint is reached. Manual titrations use color indicators to determine the endpoint.
Modern autotitrators use electrodes or other sensors to detect the equivalence point. The volume of the titrant is plotted against the measured signal to obtain a titration curve. Figure 1 shows the curve of an acid-base titration with carbonate impurities.
To learn more about the different ways to evaluate the endpoint, read our blog article «Recognition of endpoints (EP)».
After the titration, the result is calculated. Automatic titrators calculate the result themselves. The following variables are required for the calculation:
From these variables, the analyte concentration can be calculated as follows:
The formula can differ depending on the unit of the result. It is also different for back-titrations. The blog post «What to consider during back-titration» describes this calculation.
Titrations can be classified in different ways. One is the endpoint detection method, but they are most often classified by the chemical reaction utilized.
Here, an acid is titrated with a base, or vice versa. The solvent depends on the acid or base being titrated, and can be either deionized water or an organic solvent (mixture). pH electrodes are used to indicate the endpoint.
The blog post «Nonaqueous acid-base titrations – Common mistakes and how to avoid them» provides practical tips and tricks for this kind of titration.
This titration is based on a redox reaction between analyte and titrant. The titrant is a reducing agent or oxidizing agent. Common examples include iodometry, permanganometry, and cerimetry. Karl Fischer titrations also fall into the category of redox titrations. Metal electrodes are used to indicate the endpoint.
Here, the titrant is a chelating agent, such as ethylene diamine tetraacetic acid (EDTA). This titration type is used to titrate metal ions. Ion-selective electrodes (ISEs) or photometric sensors are used to indicate the endpoint.
For more information, read our blog post on photometric complexometric titration.
Analyte and titrant form an insoluble salt in this titration method. A common example is argentometry. The titration of surfactants also falls into this category. Metal electrodes or ion-selective electrodes are used to indicate the endpoint.
For more information about surfactant titration, read the blog post «The world of surfactants from the perspective of titration».
Titration is a well-established method and many standards, such as ISO, ASTM, and USP, stipulate it as an analysis method. It has lower acquisition and running costs compared to more sophisticated methods like HPLC or ICP-MS. Also, titration is an absolute method, so no calibrations are necessary.
Automated titration also offers several benefits compared to the manual method. Table 2 summarizes some of the key differences. You can find even more information in our blog post «How to avoid titration errors in your lab».
If you are considering to switch from manual to automated titration, check out the blog article «How to Transfer Manual Titration to Autotitration».
Parameter |
Manual titration |
Automatic titration |
Titrant addition |
Manually |
Automatic with piston buret |
Dosing accuracy |
0.1 mL |
25 µL |
Control |
Manually by operator |
Integrated in system or with software |
Calculation |
Manually by operator |
Integrated in system or with software |
Data traceability |
No |
Yes |
Automation possibility |
No |
Yes |
Titration is one of the oldest analytical methods. Therefore, it is well-established in various industries.
It can be classified based on the chemical reaction.
Automating the titration process with an autotitrator offers additional advantages compared to the manual method, like traceability and automated calculations.
To learn even more about titration, check out these additional resources:
Monograph: Practical aspects of modern titration
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