What is titration?
Titration is an analytical technique which allows the quantitative determination of a specific substance (analyte) dissolved in a sample. It is based on a complete chemical reaction between the analyte and a reagent (titrant) of known concentration which is added to the sample:
Analyte + Reagent(Titrant) -> Reaction Products
The titrant is added until the reaction is complete. In order to be suitable for a determination, the end of the titration reaction has to be easily observable. This means that the reaction has to be monitored (indicated) by appropriate techniques, e.g. potentiometry (potential measurement with a sensor) or with colour indicators. The measurement of the dispensed titrant volume allows the calculation of the analyte content based on the stoichiometry of the chemical reaction. The reaction involved in a titration must be fast, complete, unambiguous and observable.
A well-known example is the titration of acetic acid in vinegar with sodium hydroxide.
Titration is an analytical technique which allows the quantitative determination of a specific substance (analyte) dissolved in a sample. It is based on a complete chemical reaction between the analyte and a reagent (titrant) of known concentration which is added to the sample:
Analyte + Reagent(Titrant) -> Reaction Products
The titrant is added until the reaction is complete. In order to be suitable for a determination, the end of the titration reaction has to be easily observable. This means that the reaction has to be monitored (indicated) by appropriate techniques, e.g. potentiometry (potential measurement with a sensor) or with colour indicators. The measurement of the dispensed titrant volume allows the calculation of the analyte content based on the stoichiometry of the chemical reaction. The reaction involved in a titration must be fast, complete, unambiguous and observable.
A well-known example is the titration of acetic acid in vinegar with sodium hydroxide.
What are the advantages of titration?
+ Classical, well-known analytical technique
+ Fast
+ Very accurate and precise technique
+ High degree of automation
+ Good price/performance ratio compared to more sophisticated techniques
+ It can be used by low-skilled and trained operators
+ No need for highly specialised chemical knowledge
+ Classical, well-known analytical technique
+ Fast
+ Very accurate and precise technique
+ High degree of automation
+ Good price/performance ratio compared to more sophisticated techniques
+ It can be used by low-skilled and trained operators
+ No need for highly specialised chemical knowledge
In which industries or segments is titration used?
A non-comprehensive listing of industries using titration:
Car Manufacturing, Ceramics, Chemical industry, Coal products, Coating, Cosmetics
Detergents
Electronic, Electroplating, Energy, Explosives
Food
Glass, Government
Health
Leather
Machinery
Packing materials, Paints, Pigments, Paper&Pulp, Petroleum, Pharmaceuticals, Photo, Plastic products, Printing & Publishing
Rail, Rubber
Stone (Clay, Cement)
Textile, Tobacco
Water
Zeolite
A non-comprehensive listing of industries using titration:
Car Manufacturing, Ceramics, Chemical industry, Coal products, Coating, Cosmetics
Detergents
Electronic, Electroplating, Energy, Explosives
Food
Glass, Government
Health
Leather
Machinery
Packing materials, Paints, Pigments, Paper&Pulp, Petroleum, Pharmaceuticals, Photo, Plastic products, Printing & Publishing
Rail, Rubber
Stone (Clay, Cement)
Textile, Tobacco
Water
Zeolite
What is an autotitrator?
Automated titrators are microprocessor-controlled instruments which allow the automation of all operations involved in titration:
1. Titrant addition
2. Monitoring of the reaction (Signal acquisition)
3. Recognition of the endpoint
4. Data storage
5. Calculation
6. Results storage
7. Transfer of data to printer or computer/external system
Automated titrators are microprocessor-controlled instruments which allow the automation of all operations involved in titration:
1. Titrant addition
2. Monitoring of the reaction (Signal acquisition)
3. Recognition of the endpoint
4. Data storage
5. Calculation
6. Results storage
7. Transfer of data to printer or computer/external system
How does an autotitrator work?
Automated titrators follow a defined sequence of operations. This sequence is basically the same for all different models and brands. It is performed and repeated several times until the endpoint or the equivalence point of the titration reaction is reached (titration cycle). The titration cycle consists mainly of 4 steps:
1. Titrant addition
2. Titration reaction
3. Signal acquisition
4. Evaluation
Each step has different specific parameters (e.g. increment size) which have to be defined according to the specific titration application. More complex applications require more steps, e.g. dispensing of an additional reagent for back titrations, dilution, adjusting of the pH value. These steps and the corresponding parameters are resumed in a titration method.
Automated titrators follow a defined sequence of operations. This sequence is basically the same for all different models and brands. It is performed and repeated several times until the endpoint or the equivalence point of the titration reaction is reached (titration cycle). The titration cycle consists mainly of 4 steps:
1. Titrant addition
2. Titration reaction
3. Signal acquisition
4. Evaluation
Each step has different specific parameters (e.g. increment size) which have to be defined according to the specific titration application. More complex applications require more steps, e.g. dispensing of an additional reagent for back titrations, dilution, adjusting of the pH value. These steps and the corresponding parameters are resumed in a titration method.
What is the historical development of autotitrators?
The classical way:
Titration is a classical analytical technique widely used. Originally, it was performed by adding the titrant using a graduated glass cylinder (burette). With a tap the titrant addition was regulated manually. A change in colour indicated the end of the titration reaction (endpoint). At first, only those titrations showing a significant colour change upon reaching the endpoint were performed. Later titrations were coloured artificially with an indicator dye. The precision achieved depended mainly on the chemist's skills and, in particular, on his different colour perception.The modern way:
Titration has experienced a strong development: manual and -later- motorized piston burettes allow reproducible and accurate titrant addition. Electrodes for potential measurement replace the colour indicators, achieving higher precision and accuracy of the results. Graphical plot of potential versus titrant volume allows a more exact statement about the reaction than the colour change at the endpoint. With microprocessors the titration can be controlled and evaluated automatically. This represents a relevant step towards complete automation.
Today and tomorrow:
Developmentis not yet complete. Modern autotitrators allow the definition of complete analysis sequences achieving maximum flexibility in method development. For each application the specific method can be defined by combining simple operation functions like "Dose", "Stir", "Titrate", "Calculate" in a defined sequence. Auxiliary instruments (sample changers, pumps) help in reducing and simplifying the work load in laboratories. A further trend is the connection to computers and Laboratory Information Management Systems (LIMS).
The classical way:
Titration is a classical analytical technique widely used. Originally, it was performed by adding the titrant using a graduated glass cylinder (burette). With a tap the titrant addition was regulated manually. A change in colour indicated the end of the titration reaction (endpoint). At first, only those titrations showing a significant colour change upon reaching the endpoint were performed. Later titrations were coloured artificially with an indicator dye. The precision achieved depended mainly on the chemist's skills and, in particular, on his different colour perception.The modern way:
Titration has experienced a strong development: manual and -later- motorized piston burettes allow reproducible and accurate titrant addition. Electrodes for potential measurement replace the colour indicators, achieving higher precision and accuracy of the results. Graphical plot of potential versus titrant volume allows a more exact statement about the reaction than the colour change at the endpoint. With microprocessors the titration can be controlled and evaluated automatically. This represents a relevant step towards complete automation.
Today and tomorrow:
Developmentis not yet complete. Modern autotitrators allow the definition of complete analysis sequences achieving maximum flexibility in method development. For each application the specific method can be defined by combining simple operation functions like "Dose", "Stir", "Titrate", "Calculate" in a defined sequence. Auxiliary instruments (sample changers, pumps) help in reducing and simplifying the work load in laboratories. A further trend is the connection to computers and Laboratory Information Management Systems (LIMS).
Which types of chemical reactions are used in titration?
There are several assay reactions which are used in titration:
Acid/Base reactions:
Examples: Acid content in wine, milk. Acid content in ketchup. Content of inorganic acids like sulfuric acid.
Precipitation reactions:
Examples: Salt content in crisps, ketchup and food; Silver content in coins,
Sulfate content in mineral water; Sulfate content in electroplating bath
Redox reactions:
Examples: Content of copper, chromium and nickel in electroplating baths
Complexometric reactions:
Examples: Total hardness of water (Mg and Ca); Calcium content in milk and cheese; Cement analysis
Colloidalprecipitation reaction:
Examples: Anionic surfactant content in detergents; Anionic surfactant content in washing powders; Anionic surfactant content in liquid cleanser.
There are several assay reactions which are used in titration:
Acid/Base reactions:
Examples: Acid content in wine, milk. Acid content in ketchup. Content of inorganic acids like sulfuric acid.
Precipitation reactions:
Examples: Salt content in crisps, ketchup and food; Silver content in coins,
Sulfate content in mineral water; Sulfate content in electroplating bath
Redox reactions:
Examples: Content of copper, chromium and nickel in electroplating baths
Complexometric reactions:
Examples: Total hardness of water (Mg and Ca); Calcium content in milk and cheese; Cement analysis
Colloidalprecipitation reaction:
Examples: Anionic surfactant content in detergents; Anionic surfactant content in washing powders; Anionic surfactant content in liquid cleanser.
Titrations can be classified according to the indication principles and the chemical reaction occurring:
Potentiometry:
The concentration-dependent potential (mV) of a solution is measured against a reference potential.
Examples: Acid/Base (aqueous/non-aqueous), redox, precipitation reactions.
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