Physical Separation Methods and Calculations

The method by which an analyte is physically separated from the matrix varies depending on the nature of the sample and what form the analyte is in relative to its matrix. For example, the analyte or its matrix may be sufficiently volatile so that one or the other can be separated by evaporation at a temperature attainable by laboratory ovens or burners. In that case, the analyte weight is measured either by sample weight loss if the analyte has been evaporated or directly if the matrix has been evaporated. In either case, the weight of a container may also be involved. 

In each of these cases, the percent of the analyte is often calculated. The weight percent of an analyte in a sample is calculated using the definition of weight percent  

Following are examples of gravimetric analysis when the analyte is physically separated from the matrix. 3.6.1.1 Loss on Drying 

This is an example of a loss through volatilization (evaporation) under temperature conditions at which water would volatilize, hence the word drying. The loss can occur by elevating the temperature of the sample to just above the boiling point of water (although a different temperature may be specified) or through desiccation. This is not necessarily limited to water, however, as any sample component that volatilizes in the case of elevated temperature would be included in the weight loss. Thus it is called loss 

Evaline Robotham sets the sample tray in place in the loss-on-drying instrument. Notice the cylindrical enclosure with heating coil. 

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