The Titration Process
Titration is a technique for measuring the chemical concentrations of a reference solution. The titration method requires dissolving a sample using an extremely pure chemical reagent, called a primary standards.
The titration method involves the use of an indicator that changes color at the endpoint to signal the that the reaction has been completed. Most titrations take place in an aqueous medium but occasionally ethanol and glacial acetic acids (in petrochemistry) are employed.
Titration Procedure
The titration technique is well-documented and a proven method for quantitative chemical analysis. It is employed in a variety of industries including pharmaceuticals and food production. Titrations can be carried out manually or with the use of automated equipment. Titrations are performed by adding a standard solution of known concentration to a sample of an unknown substance until it reaches its endpoint or the equivalence point.
Titrations can take place with various indicators, the most commonly being phenolphthalein and methyl orange. These indicators are used to indicate the end of a titration, and show that the base has been fully neutralised. The endpoint may also be determined using a precision instrument such as calorimeter or pH meter.
The most commonly used titration is the acid-base titration. These are usually performed to determine the strength of an acid or the amount of a weak base. To determine titration service , the weak base is transformed into its salt and then titrated against an acid that is strong (like CH3COOH) or an extremely strong base (CH3COONa). In most instances, the endpoint is determined using an indicator, such as the color of methyl red or orange. They change to orange in acidic solutions, and yellow in neutral or basic solutions.
Isometric titrations are also very popular and are used to measure the amount heat produced or consumed in the course of a chemical reaction. Isometric titrations can be performed with an isothermal titration calorimeter or a pH titrator that measures the change in temperature of a solution.
There are a variety of reasons that could cause failure of a titration due to improper handling or storage of the sample, improper weighting, irregularity of the sample and a large amount of titrant that is added to the sample. The most effective way to minimize these errors is through a combination of user training, SOP adherence, and advanced measures for data integrity and traceability. This will drastically reduce the number of workflow errors, particularly those resulting from the handling of titrations and samples. This is because titrations can be performed on small quantities of liquid, which makes the errors more evident than they would with larger quantities.
Titrant
The titrant solution is a solution with a known concentration, and is added to the substance to be test. The solution has a characteristic that allows it to interact with the analyte to produce an uncontrolled chemical response which causes neutralization of the base or acid. The endpoint of the titration is determined when the reaction is complete and may be observed either through changes in color or through devices like potentiometers (voltage measurement with an electrode). The amount of titrant utilized is then used to determine the concentration of analyte within the original sample.
Titration is done in many different ways however the most popular way is to dissolve both the titrant (or analyte) and the analyte in water. Other solvents, such as glacial acetic acid or ethanol can also be used for specific purposes (e.g. Petrochemistry, which is specialized in petroleum). The samples must be in liquid form for titration.
There are four different types of titrations: acid-base titrations; diprotic acid, complexometric and redox. In acid-base tests the weak polyprotic is titrated with an extremely strong base. The equivalence is measured by using an indicator, such as litmus or phenolphthalein.
In laboratories, these types of titrations may be used to determine the levels of chemicals in raw materials like petroleum-based oils and other products. Titration is also utilized in the manufacturing industry to calibrate equipment and monitor quality of finished products.
In the industry of food processing and pharmaceuticals, titration can be used to test the acidity or sweetness of foods, and the amount of moisture in drugs to ensure that they have the right shelf life.
The entire process can be controlled by the use of a titrator. The titrator can automatically dispense the titrant, monitor the titration reaction for visible signal, identify when the reaction has been completed, and then calculate and save the results. It is also able to detect the moment when the reaction isn't complete and prevent titration from continuing. The benefit of using an instrument for titrating is that it requires less training and experience to operate than manual methods.
Analyte
A sample analyzer is a system of piping and equipment that extracts the sample from a process stream, conditions the sample if needed and then transports it to the appropriate analytical instrument. The analyzer can test the sample by using a variety of methods including conductivity measurement (measurement of cation or anion conductivity), turbidity measurement, fluorescence (a substance absorbs light at a certain wavelength and emits it at another), or chromatography (measurement of particle size or shape). A lot of analyzers add reagents the samples in order to enhance sensitivity. The results are recorded on a log. The analyzer is typically used for liquid or gas analysis.
Indicator
An indicator is a chemical that undergoes a distinct observable change when conditions in the solution are altered. This change can be changing in color but it could also be a change in temperature, or an alteration in precipitate. Chemical indicators can be used to monitor and control chemical reactions, including titrations. They are typically found in chemistry labs and are helpful for science demonstrations and classroom experiments.
Acid-base indicators are the most common type of laboratory indicator used for titrations. It is comprised of two components: a weak base and an acid. The indicator is sensitive to changes in pH. Both bases and acids have different shades.
A good example of an indicator is litmus, which becomes red when it is in contact with acids and blue when there are bases. Other types of indicators include bromothymol blue and phenolphthalein. These indicators are used to track the reaction between an acid and a base, and can be useful in determining the precise equivalent point of the titration.
Indicators function by having a molecular acid form (HIn) and an ionic acid form (HiN). The chemical equilibrium between the two forms is dependent on pH and adding hydrogen to the equation causes it to shift towards the molecular form. This results in the characteristic color of the indicator. The equilibrium shifts to the right, away from the molecular base and toward the conjugate acid, after adding base. This results in the characteristic color of the indicator.
Indicators can be used for other kinds of titrations well, such as redox titrations. Redox titrations are a bit more complex but the basic principles are the same. In a redox test the indicator is mixed with a small amount of base or acid in order to be titrated. The titration is complete when the indicator's colour changes when it reacts with the titrant. The indicator is then removed from the flask and washed to remove any remaining titrant.