What is Karl Fischer principle?

The principle of Karl Fischer titration is based on the oxidation reaction between iodine and sulphur dioxide. Water reacts with iodine and sulphur dioxide to form sulphur trioxide and hydrogen iodide. An endpoint is reached when all the water is consumed.

How does a coulometer work?

Coulometry determines the amount of matter transformed during an electrolysis reaction by measuring the amount of electricity (in coulombs) consumed or produced. It can be used for precision measurements of charge, and the amperes even used to have a coulometric definition.

Why Karl Fischer titration is used?

Karl Fischer (KF) titration is a redox reaction which uses the consumption of water during the reaction to measure the amount of water in a sample. It is the reference method for water determination because of its specificity, accuracy and speed of measurement. It takes place in an organic solvent.

What is Karl Fischer instrument?

A Coulometric Karl Fischer instrument is often referred to as a coulometer. The advantage of the Coulometric Karl Fischer method is the capability to accurately measure small amounts of moisture. Sensitivity of these instruments is as low as 0.1 microgram (µg) of water.

What is difference between KF and coulometer?

The main difference between the two is that with the volumetric method, the titrant is added directly to the sample by a burette. Conversely, with the coulometric method, the titrant is generated electrochemically in the titration cell.

Where is Karl Fischer used?

Applications of Karl Fischer titration These include foodstuffs, chemical reagents, pharmaceuticals and plastics. The amount of water titrated may range from one ppm to 100% water. This includes both surface water and that bound within crystals.

What are the two types of coulometry?

There are two forms of coulometry: controlled potential coulometry and controlled-current coulometry. A three-electrode potentiostat is used to set the potential in controlled potential coulometry.

What is the range of KF factor?

For coulometers, the measuring range is from 1–5 ppm to about 5%. Volumetric KF readily measures samples up to 100%, but requires impractically large amounts of sample for analytes with less than 0.05% water. The KF response is linear.

What electrode is KF titration?

The most advanced KF titration technology uses a double platinum electrode for electrochemical indication of the end point, but visual and photometric indicators are also used.

Why is DST used in KF calibration?

Answer. Sodium tartrate dihydrate is the volumetric standard for Karl Fischer titration. Under normal conditions, it is stable and non-hygroscopic. Sodium tartrate dihydrate has a stoichiometric water content of 15.66% and is primarily used for titer determination in volumetry.

Who discovered coulometry?

physicist Charles-Augustin de Coulomb
The coulomb is named after the French physicist Charles-Augustin de Coulomb (1736–1806), who discovered that the electrostatic force between two point charges is directly proportional to the size of each charge and inversely proportional to the square of the distance between the two charges (Coulomb’s law).

What is the difference between coulometry and Electrogravimetry?

In electrogravimetry, the product is weighed as a deposit on one of the electrodes. In coulometry, the quantity of electricity needed to complete the electrolysis is measured as coulombs. Both the methods are quite sensitive, rapid and accurate.

Why is methanol used as solvent in KF titration?

The role of the solvent is to contribute to the chemical reaction and to ensure the sample is releasing all its moisture content. Most liquid samples dissolve in methanol, which is the usual solvent in Karl Fischer determinations. To determine the total amount of water, the sample must dissolve completely.

Why is platinum electrode used in KF?

Principles of Karl Fischer titration The color change that signals the end point of the reaction is caused by the detection of excess iodine at the double platinum electrode which acts as the indicator, following the consumption of all the water in the sample which leads to the cessation of the reaction.

What is KF factor limit?

Standardization is valid, if concentration should be not less than 5 mg and not more than 7mg. The relative Standard deviation between two average KF factors of water and DST determined consecutively should not be more than 3.0 % [Average of two factors (2 with water and 2 with DST) to be considered for calculation.]

Which chemical is used in KF calibration?

What is coulometry PDF?

 Coulometry is an analytical method for determining the quantity of a. substance, based on the strict proportionality between the extent of a. chemical change and the quantity of electricity involved (Faraday’s law).  This method is the measurement of the quantity of the electricity.

What is electrogravimetry analysis?

Electrogravimetry is a method in which a metal is quantitatively electroplated on to an electrode, usually platinum. The amount of metal plated is determined by the difference in the weight of the electrode before and after electroplating.

What is electrogravimetry technique explain in detail?

Electrogravimetry is a method used to separate and quantify ions of a substance, usually a metal. In this process, the analyte solution is electrolyzed. Electrochemical reduction causes the analyte to be deposited on the cathode.

Why DMF is used in KF?

Hydranal-Formamide dry accelerates the speed of KF reaction. Because it can also influence the stoichiometry of the reaction, formamide should not be used at concentrations >50% by volume.

Why we are using the methanol in KF titration?

Methanol is typically used as the working medium in the titration cell. One-component volumetric reagents are easier to handle, and are usually less expensive than two-component reagents.

What is the difference between electrogravimetry and coulometry?

What is the difference between Coulometry and electrogravimetry?

Why is electrogravimetry important?

Electrogravimetry has been useful in polymer studies, copper electrodeposition, gold oxidation in an acidic medium, and passivity of iron in a sulfuric medium, as well as Ionic insertion in WO3.

How does the Metrohm 917 coulometer work?

With the 917 Coulometer teaming up with the 915 KF Ti-Touch, Metrohm offers a compact, easy-to-use, and reliable titrator for any water content. Like its volumetric counterpart, the 917 Coulometer is operated via an integrated touch-screen control unit and is capable of analyzing water concentrations down to 0.001%.

What is the Karl Fischer water determination system?

Comprehensive range of instruments and accessories for volumetric and coulometric determination of any water content in liquid, solid, or gaseous samples. Fully integrated solution for water content determination with volumetric Karl Fischer titration.

What does Metrohm do?

Metrohm AG is an internationally active producer of precision instruments for chemical analysis, in particular ion analysis, based in Herisau, Switzerland. Metrohm is the leading manufacturer of titration devices and one of the two biggest manufacturers of ion chromatography systems.

What is the range of KF of a coulometer?

For coulometers, the measuring range is from 1–5 ppm to about 5%. Volumetric KF readily measures samples up to 100%, but requires impractically large amounts of sample for analytes with less than 0.05% water. The KF response is linear.