Assay by potentiometric titration

Many compounds, especially in pharmaceuticals, require high purity. To check for sample analyte purity, you must perform titration so that one volume of the solution reacts the same as another solution.

You add measured increments of a titrant until the endpoint or equivalence point, until the entire sample has reacted. Potentiometric titration can be categorized as acid-base titration, redox reaction or precipitation titration.

Potentiometric titration requires measuring the voltage change of a titration across a sample needing purification.

It provides an adaptable, relatively affordable and highly accurate method to achieve high purity, essential to many fields, particularly pharmaceuticals. In titrations, solid samples are weighed and dissolved in a particular solvent with a known volume of a standardized titrant.

The burette portion of the instrument whether pH meter or automatic titrant houses the titrant and dispenses it into a testing vessel. The titrant flows past a reference electrode before an indicator electrode.

Reagent water is added if necessary to cover electrodes. Potentiometric titration requires measurement by electrodes of voltage change across the sample or analyte. A pair of electrodes or combination electrode is used to determine the endpoint of the titration. The endpoint describes the point at which the entire sample has reacted.

At that point, the greatest range of change of potential is reached. Voltage and volume are recorded and graphed. Potential is measured in millivolts. Plotting these values gives a sigmoid curve. The endpoint is reached with there is a rapid change in slope voltage versus volume. The endpoint can be manually located by using concentric arc templates, or microprocessors may be used to choose the endpoint automatically.

After the amount of synthesized chemical in a sample is found, its purity and concentration can be determined. Most potentiometric titrations have a lower concentration limit of approximately 10 -4 M. Software allows for minimization of any errors. Potentiometric titrations are direct titrations that require no indicator.

In some models, however, two electrodes, an indicator and a reference electrode may exist. This kind of titration is far more accurate and precise than manual titration, with high accuracy up to three digits in milliliters. A number of kinds of potentiometric titrations exist, providing options depending on the need for determining analytes.

These include acid-base, redox, precipitation and complexometric.Our website uses cookies to offer you the best possible browsing experience. By continuing to use the website, you agree to the use of cookies. Find upgrades, patches, documents, and language versions for your software here. Find out what Metrohm has to offer for environmental analysis in air, soil, and water.

Find out what Metrohm has to offer for the analysis fossil or biogenic products in accordance with international standards. Find out what Metrohm has to offer for quality control and drug manufacturing monitoring and improving in accordance with international standards.

Find out what Metrohm has to offer for food and beverage analysis in accordance with international standards.

assay by potentiometric titration

Find out what Metrohm has to offer for quality control and optimization of coating processes. Find out what Metrohm has to offer for the monitoring of the water chemistry in thermal power plants, the wet chemical processing of solar cells and battery electrolytes, or electrochemical measurements of energy storage devices.

Find out what Metrohm has to offer for analysis in polymer and plastic manufacturing. Find out what Metrohm has to offer for the analysis in the chemical industry.

New titration system for the modern laboratory: faster analysis, safer chemical handling, compliant software, more automation. High-end potentiometric titrator that meets any requirements: flexible, compliant, customizable, and automatable.

Compact, easy-to-use potentiometric titrator for a wide range of routine titrations. New basic titrator for all standard potentiometric titration applications. Entry-level, versatile potentiometric titrator for basic applications. Thermometric titrator for fast determinations if potentiometric titration cannot be applied. New volumetric Karl Fischer titrator for safe, easy, and fast water content determination.

High-end titrators for determining any water content from 0. Entry-level titrator for coulometric water content: 0.

Our range of coulometers for the determination of low water contents 0. Basic coulometer for determining low water contents down to 0. All-inclusive system for water determination in liquefied and permanent gases. High-end ion chromatography system for research applications and method development.

Entry-level ion chromatograph for water analysis and utilization as a training tool. Extend the scope of ion chromatography by interfacing your Metrohm IC with various sampling system and detection techniques. High-end modules for customized pH, ion, and conductivity measurement. Near-infrared spectroscopy analyzers for routine analysis of chemical and physical properties.

Handheld spectrometer for quick and easy identification of unknown substances. Advanced VA systems with high-performance viva software for determining traces of heavy metals with polarography and voltammetry with high sensitivity. Portable voltammetric analyzer for the determination of trace levels of arsenic, mercury, and copper in water. System combining ion chromatography and voltammetry for trace ion analysis.

We love to tackle analytical challenges at Metrohm Process Analytics. Modular analyzer platform for ultimate flexibility in customized process monitoring.

Fully autonomous system monitoring ions in aerosols and gases in ambient air. Single-method process analyzers for water and wastewater monitoring with titration, pH, ISE, or photometry methods. Taking high-precision Metrohm ion chromatography to an even higher level of autonomy, the Process IC can connect up to 20 sample streams and provide reliable multicomponent results for superior process control.Potentiometric titration is a technique similar to direct titration of a redox reaction.

It is a useful means of characterizing an acid. No indicator is used; instead the potential is measured across the analytetypically an electrolyte solution. To do this, two electrodes are used, an indicator electrode the glass electrode and metal ion indicator electrode and a reference electrode.

Reference electrodes generally used are hydrogen electrodes, calomel electrodes, and silver chloride electrodes. The indicator electrode forms an electrochemical half cell with the interested ions in the test solution. The reference electrode forms the other half cell.

assay by potentiometric titration

E sol is the potential drop over the test solution between the two electrodes. E cell is recorded at intervals as the titrant is added. A graph of potential against volume added can be drawn and the end point of the reaction is halfway between the jump in voltage. E cell depends on the concentration of the interested ions with which the indicator electrode is in contact. For example, the electrode reaction may be. Thus the potentiometric titration involve measurement of E cell with the addition of titrant.

The first potentiometric titration was carried out in by Robert Behrend at Ostwald's Institute in Leipzig. He titrated mercurous solution with potassium chloride, potassium bromide, and potassium iodide.

If potassium chloride is added to mercurous nitrate on one side, mercury I chloride is precipitated. This decreased the osmotic pressure of mercury I ions on the side and creates a potential difference. This potential difference increases slowly as additional potassium chloride is added, but then increases more rapidly. He found the greatest potential difference is achieved once all of the mercurous nitrate has been precipitated.

This was used to discern end points of titrations. Wilhelm Bottger then developed the tool of potentiometric titration while working at Ostwald's Institute. He introduced the idea of using potentiometric titrations for acids and bases that could not be titrated in conjunction with a colorimetric indicator [1]. Potentiometric titrations were first used for redox titrations by Crotogino. He titrated halide ions using potassium permanganate using a shiny platinum electrode and a calomel electrode.

He says that if an oxidizing agent is added to a reducing solution then the equilibrium between the reducing substance and reaction product will shift towards the reaction product.

The changes the potential very slowly until the amount of reducing substance becomes very small. A large change in potential will occur then once a small addition of the titrating solution is added, as the final amounts of reducing agent are removed and the potential corresponds solely to the oxidizing agent.

This large increase in potential difference signifies the endpoint of the reaction. From Wikipedia, the free encyclopedia. Elsevier, Thorburn, et al. Springer, Categories : Titration. Namespaces Article Talk. Views Read Edit View history. In other projects Wikimedia Commons.

By using this site, you agree to the Terms of Use and Privacy Policy.Home Quality Control Test. Potentiometric Titration Learn what is potentiometeric titration and how is it carried out using indicator electrode and a reference electrode. Ankur Choudhary Print Question Forum 1 comment. A convenient and useful method of determining the equivalence point of a titration, i. If an indicator electrode, sensitive to the concentration of the chemical undergoing titrimetric reaction, and a reference electrode, whose potential is not sensitive to any dissolved chemical in solution, are immersed in the solution under examination to form a galvanic cell, the potential difference between the electrodes may be sensed by a simple potentiometer or electronic device and used to follow the course of the reaction.

If a graph of the variation of potential difference is plotted as a function of the quantity of the titrant added, a sigmoid curve results with a rapidly changing portion in the vicinity of the equivalence point.

The midpoint of this linear vertical portion or the inflection point may be taken as the endpoint of the titration. In a titrimetric assay the endpoint determination is an estimate of the reaction equivalence point.

The validity of this estimate depends upon, among other factors, the nature of the solution being titirated and the concentration of the titrant.

A blank correction is employed in titrimetric assays to enhance the reliability of the endpoint determination. With potentiometric titrations, the blank correction is usually negligible. Related: Calibration of Automatic Potentiometric Titrator Apparatus The apparatus used comprises a voltmeter allowing readings to the nearest millivolt. The choice of the electrode system is governed by the nature of the titration. Table 1 summaries several acceptable electrode systems. Automatic titrators are commonly employed these days.

Two types of instruments are available. In the first one addition of titrant is carried out automatically and the electrode potential differences during the course of titration are recorded as the expected sigmoid curve.

In the second type, titrant addition is performed automatically until or preset potential or pH, representing the end - point, is reached when the addition of the titrant ceases.

Pin it. Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since Sign-up for the free email updates for your daily dose of pharmaceutical tips. Visitors are also reading:. You can ask questions related to this post here. Unknown 04 May. Get Free Updates Subscribe. View adsbypg.

Recent Posts. Join Log In 8. Get Free Updates.Analysis of composition and quality is essential at every stage of the pharmaceutical manufacturing process, from formulation development to production.

It requires the thorough characterization of pharmaceutical products and the processes by which they are developed and produced. Results of in-process tests are used to inform critical decisions made by formulators, and thus require accurate and timely results to facilitate efficient formulation development and production.

They also ensure final material quality, from content to uniformity. Among the many analytical tests used to characterize a novel formulation, titration is one of the most economical, fastest, and most reliable techniques. Both active pharmaceutical ingredients APIs and excipients such as surfactants, edible oils, minerals, and chelating agents are addressed by titration and described in the U.

Titration also continues to be a relevant technique for assay and content uniformity of tablets. Potentiometric titration in particular is a powerful tool in many facets of pharmaceutical manufacturing, from formulation development to process feedback to quality control of the finished product.

The breadth of options in automation at every step of the titration process allows it to adapt to the various dosage forms, analytes, and goals needed to ensure tight control of incoming materials and high quality of finished pharmaceutical products.

Automated titration offers many benefits over manual titration, providing more consistency and objectivity at each step, from sample preparation to determination of endpoint. It also improves the accuracy and repeatability of results, reduces waste of time and materials through human error, and increases the throughput of the analytical lab. The characterization of a novel formulation requires distinct and varied analytical tests, both during processing and on the final material.

The results of in-process tests are used to inform critical decisions made by formulators.

Chloride titrations with potentiometric indication

Receiving timely results is key to efficient formulations development and production, as every tablet, vial, tube, or bag of product in a batch must have the same active substance content as stated on the packaging.

Various analytical methods are available for the exact determination of APIs, defined by the standard operating procedures in the European Pharmacopoeia and the USP.

Current USP-NF monographs recommend potentiometric titration for assay of about active pharmaceutical ingredients in both aqueous and non-aqueous media. The purity of sulfanilamide, often employed for treatment of vaginal yeast infections, can be determined in aqueous solution by automatic, potentiometric titration using sodium nitrite as the titrant Figure 1.

Potassium bromide is added to the solution, as bromide ions act as catalyst for the diazotization titration. Using the Pt Titrode electrode, purity of the sample is determined in as little as three to five minutes, including time for electrode maintenance. Samples of fats and oils or components of acid-base mixtures often cannot be titrated in aqueous media.

In these cases, solvent selection is key to obtaining accurate, repeatable results, particularly when isolating APIs from interfering excipients and carriers. Ketoconazole is an antifungal drug used in the treatment of fungal infections and is prescribed as a tablet, cream for ringworm or cutaneous candidiasisor shampoo for dandruff. Excipients often comprise a large fraction of pharmaceutical products because they are used as fillers or bulking agents for formulations containing low concentrations of potent active ingredients.

They also perform important functions like long-term stabilization and enhancement of the active ingredient. In the manufacturing process excipients can facilitate powder flow or non-stick properties, enhance stability of intermediates, and extend shelf life.

While the most common dosage forms of pharmaceuticals are tablets and injectables, many formulations are also delivered as aerosols, capsules, creams, films, foams, and gels. Excipients play a key role in formulation and need to be of high purity to meet the needs and regulatory requirements of the pharmaceutical industry.Our website uses cookies to offer you the best possible browsing experience.

By continuing to use the website, you agree to the use of cookies. Find upgrades, patches, documents, and language versions for your software here. Find out what Metrohm has to offer for environmental analysis in air, soil, and water. Find out what Metrohm has to offer for the analysis fossil or biogenic products in accordance with international standards. Find out what Metrohm has to offer for quality control and drug manufacturing monitoring and improving in accordance with international standards.

Find out what Metrohm has to offer for food and beverage analysis in accordance with international standards.

Autotitrator Tutorial

Find out what Metrohm has to offer for quality control and optimization of coating processes. Find out what Metrohm has to offer for the monitoring of the water chemistry in thermal power plants, the wet chemical processing of solar cells and battery electrolytes, or electrochemical measurements of energy storage devices. Find out what Metrohm has to offer for analysis in polymer and plastic manufacturing.

Find out what Metrohm has to offer for the analysis in the chemical industry. New titration system for the modern laboratory: faster analysis, safer chemical handling, new software, more automation. High-end potentiometric titrator that meets any requirements: flexible, compliant, customizable, and automatable. Compact, easy-to-use potentiometric titrator for a wide range of routine titrations. New basic titrator for all standard potentiometric titration applications.

Entry-level, versatile potentiometric titrator for basic applications. Thermometric titrator for fast determinations if potentiometric titration cannot be applied. New volumetric Karl Fischer titrator for safe, easy, and fast water content determination.

assay by potentiometric titration

High-end titrators for determining any water content from 0. Entry-level titrator for coulometric water content: 0. Our range of coulometers for the determination of low water contents 0. Basic coulometer for determining low water contents down to 0.

All-inclusive system for water determination in liquefied and permanent gases. High-end ion chromatography system for research applications and method development. Entry-level ion chromatograph for water analysis and utilization as a training tool. Extend the scope of ion chromatography by interfacing your Metrohm IC with various sampling system and detection techniques. High-end modules for customized pH, ion, and conductivity measurement. Near-infrared spectroscopy analyzers for routine analysis of chemical and physical properties.Potentiometric titration is a method of chemical analysis.

This technqiue relies on the measurement of electromotive force EMF of a solution using a set of indicator and reference electrodes. The potential or EMF of a solution depends on the nature and concentration of the ions of the test substance. The EMF or potential is measured in millivolts mV using a potentiometer having an indicator and reference electrode. In a potentiometric titration, the endpoint is determined by measuring the changes in potential of the solution.

This change in potential is caused due to the addition of titrant.

Potentiometric Titration

During the process, the addition of titrant causes changes in the activity and also the concentration of ions in the solution. The instrumentation has two electrodes, a beaker, stirrer and a burette. The electrodes include a reference electrode and an indicator electrode.

Saturated Calomel electrode is used as a reference electrode while a glass electrode is employed as an indicator electrode. Titration is done by taking the test solution in a beaker and adding the titrant from the burette. The end point is determined by the indicator method. If not, then a titration curve is drawn. From this titration curve, a graph is plotted to determine the endpoint. There are three types of titrations curves. In the potentiometric titrations, the rate of change in potential is maximal at the endpoint.

This can be determined by three kinds of curves like. Acid-base titrations: This potentiometric titration can be used for both aqueous and nonaqueous titrations. The indicator electrode would be a glass electrode and a reference electrode can be a S.

This potentiometric titration can analyze all types of acid-base titration. Further, the mixture of acids, polybasic acids can also be analyzed. Redox titrations: The redox titrations are done by using platinum foil as an indicator electrode and Sat.

Calomel electrode or silver chloride electrode as a reference electrode. The endpoint is denoted by mV. Here E 0 is standard potential, n is the number of electrons involved in the reaction, cons.


thoughts on “Assay by potentiometric titration

Leave a Reply

Your email address will not be published. Required fields are marked *