Moisture Analysers - Thermo Fisher

Sartorius WDS 400: Selective detection of surface water,capillary water and water of crystallizationWater, not moistureThermogravimetric methods, such as theoven drying method, use the weight loss of asample to determine the total content of allvolatile components and not, however, thepure water content. As a rule, the latter taskis performed using electrochemical techniquesthat are based on the principle ofcoulometry (coulomb = electric charge). Themost commonly known methods are coulometricKarl Fisher titration for solid and liquidsamples and the phosphorus pentoxidemethod for trace analysis of gases. However,both methods require complicated equipment;moreover, KF titration necessitates theuse of additional chemicals in order to performan analysis. The WDS 400 Water DetectionSystem from Sartorius combines thesethree standard methods into a high-resolutionand easy procedure for selective detectionof water in solids and pastes.Get all three in oneThe WDS 400 adopts the principle of convectionheating from the oven drying methodin order to drive out the entire moisture froma sample. A ceramic disc coated withextremely hygroscopic phosphorus pentoxideP 2 O 5 completely absorbs the water from theresulting gas mixture and bonds water moleculesto phosphoric acid H 3 PO 4 on the discsurface in a chemical reaction. By coulometry,i.e., by an electric current generated at theceramic disc, phosphoric acid is broken downinto phosphorus pentoxide P 2 O 5 , hydrogen Hand oxygen O. Based on Faraday’s law, it isknown how much current is necessary inorder to split off all hydrogen atoms from achemical compound. Thus, the WDS 400 usesthe amount of electric current to calculatethe quantity of water driven out of a sample.Highly accurate and selectiveThis combination method works so accuratelythat it is even possible to detect one singlemicrogram of water. Beyond that, theWDS 400 enables water fractions to bedifferentiated according to surface water,capillary water and water of crystallization(the latter is chemically bound water).Easy operationAll the user has to do is just weigh-in asample. The WDS 400 does not require anycomplicated handling of detection reagents,many of which are toxic.For measurement of the water content, theuser can choose the type of carrier gas, eithernitrogen (Class 5.0) or room air. For usingroom air, the WDS 400 has a built-in pumpand a drying unit.Dry nitrogen Oven up to 400°C Nitrogen + H 2 O P 2 O 5 + H 2 O cell Dry nitrogenwith H 2 + O 2r r r▲Electronics▲rl▲▼rrBalancePCPrinter