Primary Moisture techniques involve direct chemical determination of water content, usually by extracting the moisture from the product. 

All primary methods are destructive and time consuming. Primary methods are performed off-line, but are usually very accurate.  Small sample size may not adequately represent bulk product. 

The most common primary method is weight loss, in which a sample is weighed, dried until no further weight loss and then re-weighed. 

Other methods are Karl-Fischer and Toluene Distillation. The accuracy of all off-line primary methods is dependent upon laboratory instrument accuracy and the skill of lab personnel. 

Since off-line methods require taking a product sample from the process, the sampling method must provide consistent product samples for testing.