Please guide, what is the difference between LOD and Moisture Analyser method
Karl Fischer titration is a classic titrationmethod in analytical chemistry that uses coulometric or volumetric titration to determine trace amounts of water in a sample. It was invented in 1935 by the German chemist Karl Fischer. Today, the titration is done with an automated Karl Fischer titrator.
The main compartment of the titration cell contains the anode solution plus the analyte. The anode solution consists of an alcohol (ROH), a base (B), SO2 and I2. A typical alcohol that may be used is ethanol or diethylene glycol monoethyl ether, and a common base is imidazole.
The titration cell also consists of a smaller compartment with a cathode immersed in the anode solution of the main compartment. The two compartments are separated by an ion-permeable membrane.
The Pt anode generates I2 when current is provided through the electric circuit. The net reaction as shown below is oxidation of SO2by I2. One mole of I2 is consumed for each mole of H2O. In other words, 2 moles of electrons are consumed per mole of water.
B·I2 + B·SO2 + B + H2O → 2BH+I− + BSO3
BSO3 + ROH → BH+ROSO3−
The end point is detected most commonly by a bipotentiometric method. A second pair of Pt electrodes are immersed in the anode solution. The detector circuit maintains a constant current between the two detector electrodes during titration. Prior to the equivalence point, the solution contains I− but little I2. At the equivalence point, excess I2appears and an abrupt voltage drop marks the end point. The amount of charge needed to generate I2 and reach the end point can then be used to calculate the amount of water in the original sample.
In lod sample in weigh and heated at 105 degre.
KF is just for water content
lod is for any solvent moisture
Why maintain 105 degree Celsius for LOD? and is it suitable for all API?
As i know, KF titration is for the detection of traces of water content in terms of moisture. But LOD is for the analysis of volatile substance including water present in the product.
LOD conditions should be decided on the basis of melting range of API and its thermal stability.
In some extreme case, LOD may not be applicable for an API due to its undesirable physical characteristics. In such cases, residual solvents are unusually monitored by GC-HS.
LOD is used to understand the surface adsorbed residual solvents/ water resulting from manufacturing process. It cannot, however give information about crystal bound solvent (solvate) and water (hydrate).
Karl-fisher titration is used to understand total water namely surface and bound water in a given sample.
The main requirement of KF titration is to get a clear solution media from the sample to be analyzed. Since sample dissolves, all of the water that are coordinated in crystal and present on surface are released from sample and analyzed during the titration.