9.5 : 定性分析

Qualitative analysis is the identification of elements, ions, or compounds in an unknown sample. It is the first among the three types of analysis based on the hierarchy of purpose and the kind of information required.

Qualitative analysis is performed via classical and instrumental methods.

The classical methods are based on the perceptible outcome of selective or specific chemical reactions identifiable by the human senses.

Selective reactions have a degree of preference towards the analyte compared to the other components in the sample. In contrast, specific reactions occur only with the analyte.

Sample preconditioning, such as precipitation or extraction, enhances the selectivity of a reaction towards the analyte.

In comparison, the instrumental methods measure a distinguishable physical property of the analyte. For example, individual peaks of an infrared spectrum indicate a specific functional group in the sample.