Sartorius WDS 400Selective detection of surface water, capillary water and water of crystallization

Thermogravimetry Water, not moisture
StDry nitrogenOven up to 400°CNitrogen + H 2 OP 2 O 5 + H 2 O cellDry nitrogen with H Thermogravimetric methods, such as the oven drying method, use the weight loss of a sample to determine the total con-tent of all volatile components and not,however, the pure water content. As a rule, the latter task is performed using electrochemical techniques that arebased on the principle of coulometry(coulomb = electric charge). The most commonly known methods are coulo- metric Karl Fisher titration for solid andliquid samples and the phosphorus pen- toxide method for trace analysis of gases. However, both methods require compli- cated equipment; moreover, KF titration necessitates the use of additional chemi- cals in order to perform an analysis. TheWDS 400 Water Detection System from Sartorius combines these three standardmethods into a high-resolution and easy procedure for selective detection ofwater in solids and pastes.
2 + O 2 r r r Electronics ▲▲▲▼ Backweighing r lr r Balance PCPrinter Get all three in one Highly accurate and selective The WDS 400 adopts the principle of convection heating from the oven drying method in order to drive out the entiremoisture from a sample. A ceramic disccoated with extremely hygroscopic phos- phorus pentoxide P2O5 completely absorbs the water from the resulting gasmixture and bonds water molecules tophosphoric acid H3PO4 on the disc sur- face in a chemical reaction. By coulome- try, i.e., by an electric current generatedat the ceramic disc, phosphoric acid isbroken down into phosphorus pentoxide P2O5, hydrogen H and oxygen O. Based on Faraday’s law, it is known how muchcurrent is necessary in order to split off all hydrogen atoms from a chemicalcompound. Thus, the WDS 400 uses the amount of electric current to calculatethe quantity of water driven out of asample. 18 This combination method works so accu- rately that it is even possible to detect one single microgram of water. Beyondthat, the WDS 400 enables water frac-tions to be differentiated according to surface water, capillary water and water of crystallization (the latter is chemicallybound water). Easy operation All the user has to do is just weigh-in asample. The WDS 400 does not require any complicated handling of detectionreagents, many of which are toxic. For measurement of the water content,the user can choose the type of carriergas, either nitrogen (Class 5.0) or room air. For using room air, the WDS 400 has a built-in pump and a drying unit.
Coulometry Microwave resonance NIR spectroscopy