What Is Titration?

Titration is an analytical technique that allows the quantitative determination of a specific substance dissolved in a sample by addition of a reagent with a known concentration. It is based on a complete chemical reaction between the substance (analyte) and a reagent (titrant).

Titrant is added until the reaction is complete. To be suitable for determination, the end of the titration reaction must be easily observable when monitored (indicated) by appropriate techniques, e.g., potentiometry (potential measurement with a sensor) or through a color change.

The measurement of the dispensed titrant volume allows the calculation of the analyte content based on the stoichiometry of the chemical reaction. For accuracy, a titration reaction should be fast, complete, unambiguous and observable.

While classical titration was performed by manually adding titrant using a tap with a graduated glass cylinder known as a burette, modern automated titration enables accurate, repeatable titrant addition and a more robust plot of potential vs. titrant volume. However, manual titration remains a mainstay in many labs around the world (see manual vs. automated titration below). The basic theory behind manual and automated titration is the same.

More information of what titration is, can be found at the Basics of Titration guide.

• Why is Titration Important and How is it Used in Industries?
• What Are the Types of Titration?
• What Are the Advantages of Titration?
• What Are the Differences between Manual vs. Automated Titration?
• What is a Titration Curve?
• What is the Difference Between Endpoint and Equivalence Point Titration?
• How to Calculate Molarity / Molarity Equation / Molar Concentration
• How to Achieve Accurate Titration Results?
• Basic Terminology in Titration

Titration is a fast, accurate and established analytical technique that is widely applied in research, product development, and quality control. When compared to certain other analytical methods, it is cost-effective, highly accurate, and accepts a high degree of automation. These factors can make improving workflow productivity easy, as titration can be performed by operators without specific chemistry knowledge. Industries that use titration chemistry include agriculture, biotech, chemicals, cosmetics, electronics, food and beverage, paints and pigments, paper and pulp, petrochemicals, and pharmaceuticals.

• Titration is a well-established analytical technique: Titration is one of the oldest and most commonly used quantitative analytical methods. Manual, semi-automated, and fully automated titrations have been extensively developed and are employed in a wide range of industries.
  
• It is a fast procedure: In the case of manual titrations, a buret, a titrant, and a suitable endpoint indicator are the only required items. The titrant is added to the sample in the buret until the reaction is complete and easily observable. The measurement of the dispensed titrant volume allows the calculation of the analyte content based on the stoichiometry of the chemical reaction.
  Automatic titrations are even faster and accounting for a significant amount of time saved. Automation allows high throughput with minimal operator effort, and supports the user in terms of quality and data security by improving reproducibility and avoiding transcription errors. Automation boosts productivity and increase efficiency.
  
• Very accurate and precise technique: At first, only those titrations showing a significant color change upon reaching the endpoint were performed. Later titrations were colored artificially with an indicator dye. The precision achieved depended mainly on the chemist's skills and, in particular, on his ability for perception of different colors. Nowadays, titration has experienced a strong development: manual and later motor-driven piston burettes allow accurate and repeatable titrant addition. Electrochemical sensors replace the color indicators, thus achieving higher precision and accuracy of results. The graphical plot of potential versus titrant volume and mathematical evaluation of the resulting titration curve provides a more exact statement about the reaction than the color change at the endpoint. With microprocessors the titration can be controlled and evaluated automatically, which represents an important step towards automation.
  
• Highest degree of automation possible: A titrator is an instrument, which allows the automation of all operations involved in titration: titrant addition, monitoring of the reaction (signal acquisition), recognition of the endpoint, data storage, calculation and results storage. All the operator has to do is place the samples on the rack of the titrator and start the method.
  -Learn more about opportunities and benefits of automation with our Titration Automation Guide
  
• Automated titrations can be used by low-skilled and trained operators: In the case of manual titrations, a lab technician follows a detailed, standardized procedure (or method) and applies his or her skills and knowledge to the task. The results are then calculated and documented.
  Automated titrations are easy to perform and there is no need for highly specialized chemical knowledge. Titration methods are programmed once and can be re-used by any user simply by pressing a button. Results are then generated automatically.
  
• Good price/performance ratio compared to more sophisticated techniques.

Titration is a quantitative analytical technique used to determine the unknown concentration of an analyte of interest (the substance to be analyzed). It is performed by gradually adding an exactly known quantity of a substance (the tritrant), which reacts with our analyte in a definite proportion, to the sample we want to analyze. The measurement of the dispensed titrant volume allows the calculation of the analyte content based on the stoichiometry of the chemical reaction.

The titrant is added until the chemical reaction is complete and the end of the titration reaction is easily detected by appropriate techniques (e.g. potentiometry or color change of a suitable indicator). The reaction involved in a titration must therefore be fast, complete, unambiguous and observable.

For more information and comparison, please see here:

Titration curves illustrate the qualitative progress of a titration. They allow a rapid assessment of the titration method. A distinction is made between logarithmic and linear titration curves.

The titration curve has basically two variables:

• The volume of the titrant as the independent variable. The signal of the solution, e.g. the pH for acid/base titrations as the dependent variable, that depends on the composition of the two solutions.
• The titration curves can take 4 different forms, and should be analysed with the appropriate evaluation algorithms. These four forms are: the symmetric curve, asymmetric curve, the minimum/maximum curve, and the segmented curve.

Endpoint titration mode (EP):

The endpoint mode represents the classical titration procedure: the titrant is added until the end of the reaction is observed, e.g., by a color change of an indicator. With an automatic titrator, the sample is titrated until a predefined value is reached, e.g. pH = 8.2.

Equivalence point titration mode (EQP):

The equivalence point is the point at which the analyte and the reagent are present in exactly the same quantities. In most cases it is virtually identical to the inflection point of the titration curve, e.g. titration curves obtained from acid/base titrations. The inflection point of the curve is defined by the corresponding pH or potential (mV) value and titrant consumption (mL). The equivalence point is calculated from the consumption of titrant of known concentration. The product of concentration of titrant and the titrant consumption gives the amount of substance which has reacted with the sample. In an autotitrator the measured points are evaluated according to specific mathematical procedures which lead to an evaluated titration curve. The equivalence point is then calculated from this evaluated curve.

The amount-of-substance concentration of a solution of an entity X (symbol c(X)) is the amount of substance n divided by the volume V of the solution.

N is the number of molecules present in the volume V (in litres), the ratio N/V is the number concentration C, and N_A is the Avogadro constant, approximately 6.022×10²³ mol⁻¹.

The usual units employed in analysis are mol/L and mmol/L.

Obtaining precise and accurate titration results requires an understanding of how to minimize factors that can negatively influence accuracy, as well as choosing the right titration method.

Reducing factors that negatively impact the accuracy of results requires an understanding of the types of errors that can be present in all measurement activities: systematic errors, random errors, and workflow errors.

Systematic errors

A systematic error is an error that is constant or drifting due to a consistent mistake made during analysis. Typical systematic errors in titration include:

• Incorrect analytical method or titration formula
• Sampling errors or wrong sample sizes due to a consistent, unrecognized weighing error
• False or missing blank values, incorrect sensor adjustment
• Too high a speed for the reaction or electrode response

Once the source of a systematic error is identified in a titration process, it is usually easy to correct.

Random errors

A random error is a component of the overall error that varies in an unpredictable fashion and is usually harder to identify. Typical sources of random errors in titration include:

• Poor sample handling
• Inadequate equipment (low balance resolution, wrong glassware grade, etc.)
• Incorrect method parameters (increments too large, insufficient waiting time)
• Bubbles in burette tubes or ineffective rinsing between samples
• Lack of operator training or inconsistent environmental conditions

If the source of a random error cannot be identified, the number of replicates must be increased to obtain a more trustworthy mean value. This generally leads to wasted sample, reagents and time.

Workflow errors

These types of errors are often time consuming and occasionally very expensive to trace, especially when time or cost pressures are present. Typical workflow errors include:

• Notation/transcription errors (e.g., copying data, mislabeling samples)
• Calculation errors
• Mixing up samples and/or reagents
• Wrong sample sizes
• Errors in system setup, instrument operation, or cleaning (not clearing bubbles from the lines, for example)

A combination of user training, SOP adherence, and advanced measures for data traceability and integrity will drastically reduce workflow errors.

Sample handling

Sample handling errors are perhaps the biggest error source in a titration workflow. The homogeneity of the sample, storage problems, incorrect sample size, and weighing errors are examples.  

In terms of size, the sample should be large enough to be representative, however not so large that repeated burette fillings become necessary during the titration. The ideal titration should give a titrant consumption of between 30 and 80% of a single burette volume. If inhomogeneity requires the sample to be larger, then a more concentrated titrant should be used.

The sample should also be large enough so that sample-measurement errors are minimized. This typically requires a suitable balance and ensuring that the sample size exceeds the balance’s minimum net sample weight requirements. The minimum weight is usually a factor of your desired or given process tolerance for weighing. For example, USP41 specifies a maximum permissible error of 0.1% in weighing results. In order to ensure accurate weighing, your individual process tolerances should be 2 to 4 times smaller to ensure an adequate safety margin. For non-USP regulated industries, 1% is a typical process tolerance.

For example, when standardizing a KF titrant with disodium tartrate dehydrate, a sample of 50 mg is typically required due to methanol solubility issues. To ensure a weighing uncertainty of less than 0.1%, a balance with a readability of at least 0.01 mg is needed. However, if pure water is being used to standardize a KF reagent and ensure adequate titrant consumption, 7.5 to 20 mg of water must be used. In this case, a balance with 0.01 mg readability may not fulfill USP guidelines for accurate weighing for sample weights over 14 mg. In the case of liquid samples, the appropriate grade of glassware or volumetric apparatus must also be used, and care must be taken to avoid handling errors. To help minimize avoidable error sources during titration methods, download our free poster to learn how to identify and avoid titration errors.

The following titration definitions may make it easier for you to learn all you need to know about titration.

Analyte: Specific chemical species in a sample of which the content or amount is determined by titration.

End of titration: The desired endpoint or equivalence point at which titration is terminated and titrant consumption evaluated. More than one equivalence point may occur during the same titration.

Endpoint: The point at which the end of the titration reaction is observed (typically by color change or another titration indicator). To define titration along with its endpoint represents the classical technique.

Equivalence point: The point at which the number of entities (equivalents) of the added titrant is the same as the number of entities of sample analyte.

Indication: The procedure to follow the reaction and detect the end of the titration. Generally, indication is made using potentiometry (electrodes) or color indicators.

Parallax: The difference in the apparent position of an object based on the observer’s line of sight. In titration, this phenomenon must be considered when visually observing liquid menisci in a burette.

Primary standard: A certified, highly pure substance used for the accurate determination of titrant concentration.

Signal acquisition: Signal acquisition is the monitoring of physical phenomena to obtain digital or numeric values at certain points (such as a titration experiment endpoint or equivalence point).

Standardization: The use of a highly pure reference chemical substance (standard) to determine titrant concentration.

Stoichiometry: The mole/mass relationships between reagents and products in titration. Titration reagents react according to fixed relationships, so if the amount of separate reactants is known, the amount of the product can be calculated. If the amount of one reactant is known and the amount of products can be determined, the amount of other reactants can also be calculated.

Titrant: A solution of a certain chemical reagent that is standardized in terms of concentration so it can be used for accurate titration.

Titration: A quantitative chemical analysis in which a defined amount of titrant reacts quantitatively with the sample compound being analyzed. From the volume of titrant consumed, the amount of sample compound is calculated based on the stoichiometry of the assay reaction. Also known as volumetry or titrimetry.

Titration curve: Titration curves illustrate the qualitative progress of a titration. The curve generally uses the volume of the titrant as the independent variable and the solution as the dependent variable. A curve allows rapid assessment of the titration method. Curves take four forms: symmetric, asymmetric, minimum/maximum, and segmented.

Titration cycle: The cycle that is performed and repeated until the endpoint or the equivalence point of the titration reaction is reached. The titration cycle consists primarily of four steps: titrant addition, titration reaction, signal acquisition, and evaluation.

Titration equation: A series of titration formulas that allow the calculation of the mass molarity of solid samples, the concentration of acid and base solutions, the concentration of diluted solutions, and the titrant consumption after a direct titration. For easy calculation of titration results, visit our Titration Calculator.

Titration theory: Titration theory explores the determination of a product related to its concentration by observing a titration reaction using either physical or electrochemical methods. Knowing the exact concentration of a species, product, or chemical function helps to ensure process efficiency and/or product quality.