The Titration Process
Titration is the process of measuring the amount of a substance that is unknown by using a standard and an indicator. The
titration process involves a number of steps and requires clean equipment.
The process starts with the use of a beaker or Erlenmeyer flask that contains an exact amount of analyte and a small amount of indicator. This is placed on top of an encasement that contains the titrant.
Titrant
In titration, a titrant is a solution that has an established concentration and volume. This titrant is allowed to react with an unidentified sample of analyte until a specified endpoint or equivalence point has been reached. The concentration of the analyte may be estimated at this point by measuring the amount consumed.
To conduct a titration, a calibrated burette and an syringe for chemical pipetting are required. The syringe which dispensing precise amounts of titrant are used, and the burette is used to measure the exact volume of titrant added. For most titration methods the use of a special indicator used to monitor the reaction and to signal an endpoint. This indicator can be one that changes color, such as phenolphthalein or an electrode that is pH.
In the past, titrations were conducted manually by laboratory technicians. The process depended on the ability of the chemist to recognize the change in color of the indicator at the point of completion. Instruments used to automatize the process of titration and provide more precise results is now possible by the advancements in titration technologies. A Titrator can be used to perform the following functions: titrant addition, monitoring of the reaction (signal acquisition) as well as recognition of the endpoint, calculation and data storage.
Titration instruments reduce the requirement for human intervention and assist in removing a variety of errors that occur in manual titrations, including: weighing errors, storage issues, sample size errors as well as inhomogeneity issues with the sample, and re-weighing mistakes. Furthermore, the high level of automation and precise control offered by titration equipment significantly increases the accuracy of the titration process and allows chemists to finish more titrations in a shorter amount of time.
The food & beverage industry uses titration techniques to control quality and ensure compliance with the requirements of regulatory agencies. Particularly, acid-base titration is used to determine the presence of minerals in food products. This is done using the back titration method using weak acids and solid bases. This kind of titration is usually performed using the methyl red or methyl orange. These indicators change color to orange in acidic solutions, and yellow in basic and neutral solutions. Back titration is also employed to determine the concentrations of metal ions, such as Ni, Zn and Mg in water.
Analyte
An analyte is a chemical compound that is being examined in lab. It could be an inorganic or organic substance, such as lead found in drinking water, but it could also be a biological molecular, like glucose in blood. Analytes are usually determined, quantified, or measured to provide data for research, medical tests or for quality control.
In wet techniques an analytical substance can be identified by observing a reaction product from chemical compounds that bind to the analyte. The binding process can cause a change in color, precipitation or other detectable changes that allow the analyte to be identified. A number of analyte detection methods are available, including spectrophotometry immunoassay, and liquid chromatography. Spectrophotometry, immunoassay, and liquid chromatography are the most common methods of detection for biochemical analytes. Chromatography is utilized to determine analytes from various chemical nature.
Analyte and indicator dissolve in a solution and an amount of indicator is added to it. The mixture of analyte indicator and titrant is slowly added until the indicator changes color. This signifies the end of the process. The amount of titrant used is then recorded.
This example demonstrates a basic vinegar titration using phenolphthalein to serve as an indicator. The acidic acetic (C2H4O2 (aq)), is being titrated by the basic sodium hydroxide, (NaOH (aq)), and the endpoint can be determined by comparing the color of the indicator to the color of the titrant.
A good indicator changes quickly and strongly, so that only a small amount is needed. A useful indicator also has a pKa close to the pH of the titration's ending point. This minimizes the chance of error the experiment by ensuring that the color changes occur at the right moment in the titration.
Another method of detecting analytes is by using surface plasmon resonance (SPR) sensors. A ligand - such as an antibody, dsDNA or aptamer - is immobilised on the sensor along with a reporter, typically a streptavidin-phycoerythrin (PE) conjugate. The sensor is then incubated with the sample, and the reaction is recorded. It is directly linked with the concentration of the analyte.
Indicator
Chemical compounds change colour when exposed to bases or acids. Indicators can be classified as acid-base, reduction-oxidation, or specific substance indicators, with each type having a characteristic transition range. As an example, methyl red, a popular acid-base indicator turns yellow when in contact with an acid. It is colorless when it is in contact with the base. Indicators can be used to determine the endpoint of the Titration. The change in colour could be a visual one or it may occur through the formation or disappearance of the turbidity.
A good indicator will do exactly what is intended (validity), provide the same result if measured by multiple individuals in similar conditions (reliability), and only take into account the factors being assessed (sensitivity). Indicators are costly and difficult to collect. They are also often indirect measures. They are therefore prone to error.
It is essential to be aware of the limitations of indicators, and ways to improve them. It is crucial to realize that indicators are not a substitute for other sources of information, such as interviews or field observations. They should be used alongside other indicators and methods when reviewing the effectiveness of programme activities. Indicators are a valuable tool for monitoring and evaluation however their interpretation is critical. An incorrect indicator could cause misguided decisions. A wrong indicator can cause confusion and mislead.
For instance the
titration process in which an unknown acid is determined by adding a concentration of a different reactant requires an indicator that lets the user know when the titration is completed. Methyl yellow is an extremely popular choice because it is visible even at very low concentrations. It is not suitable for titrations with acids or bases which are too weak to affect the pH.
In ecology, an indicator species is an organism that communicates the status of a system by changing its size, behaviour or rate of reproduction. Indicator species are often monitored for patterns over time, which allows scientists to evaluate the effects of environmental stressors such as pollution or
titration process climate change.
Endpoint
Endpoint is a term used in IT and cybersecurity circles to describe any mobile device that connects to a network. These include laptops, smartphones, and tablets that users carry in their pockets. These devices are in essence in the middle of the network and are able to access data in real-time. Traditionally networks were built using server-centric protocols. With the increasing mobility of workers and the shift in technology, the traditional approach to IT is no longer sufficient.