Presumptive tests are used to determine whether a specific chemical is present in a solution. These tests are commonly used to detect whether someone has drugs in their system.
A presumptive test indicates whether there has been a reaction between a substance and a particular chemical. It will demonstrate this chemical reaction by changing color. It is used in laboratory settings as part of the process to analyze substances, such as blood.
On the other hand, confirmatory tests use instrumental analysis in order to provide the same information. This often includes a multi-step process where the substance is separated in order to analyze each component and their characteristics.