Huazheng Electric HZWS-X2 Oil Karl Fischer Moisture Analyzer

Instrument Description

The instrument of Coulometric Karl Fischer titrators is an used for Coulometric water determination according to Karl Fischer. The instrument meets the IEC60184 standard，The instrument is designed for usage as a titrator in analytical laboratories.Its main application field is volumetric titration.

The present instrument is suitable for processing chemicals and flammable samples. The usage of this titrators therefore requires that the user has basic knowledge and experience in the handling of toxic and caustic substances. Knowledge with respect to the application of the fire prevention measures prescribed for laboratories is also mandatory.

Modes

Coulometric KF titration with automatic blank deduction Endpoint indication Voltametric, AC indication Iodine production Pulse with variable current strength and length.

Current at the generator electrode: 100, 200, 400 mA

Titration speed max： 40 ug/s

Determination range 0 to200 mg

Resolution 0.1 ug

Reproducibility Sample: Reagent manufacturer's standard.With 10 ug...1000 ug : ± 2 ug

With >1000 ug : 0.2% or better

Drift compensation automatic

Display Graphical LCD, 240 x 128 dots, LED back-lit

Printer Built-in thermal printer, Paper width 57 mm

Memory Data storage 500 results

Stirrer control coordinated with the titration process

RS232 interface computer connection

Principle Of Coulometric KF Determinations

The coulometric Karl Fischer titration is a version of the classical water determination method developed by Karl Fischer. The traditional method utilises a methanolic solution of iodine, sulphur dioxide and a base as buffer. Several reactions run in the titration of a water-containing sample and can be summarised by the following overall equation:

H2O + I2 + [RNH]SO3CH3 + 2 RN [RNH]SO4CH3 + 2 [RNH]I

According to the above equation, I2 reacts quantitatively with H2O.

This chemical relation forms the basis of the water determination.

The classical Karl Fischer method has undergone constant development in the past years. This further development has involved not only refinement and automation of the reagent dispensing, but also improvement of the end point indication and the reagents. Despite the progress made, the classical, volumetric Karl Fischer method suffers from the disadvantage that the reagents are not completely stable resulting in the need to redetermine the titer atintervals.

In the coulometric Karl Fischer titration, the iodine needed is generated directly in the electrolyte by electrochemical means ("electronic buret"). The rigorously quantitative relationship between the electric charge and the amount of iodine generated is used for high-precision dispensing of the iodine. As the coulometric Karl Fischer method is an absolute determination no titer need be determined. It is necessary only to ensure that the reaction which generates the iodine runs with 100% current efficiency. With the reagents available today this is always the case.

The end point is indicated voltametrically by applying an alternating current of constant strength to a double Pt electrode. This results in a voltage difference between the Pt wires of the indicator electrode which is drastically lowered in the presence of minimal quantities of free iodine. This fact is used to determine the end point of the titration.