An Introduction to qualitative and semi quantitative testing
Qualitative and semi-quantitative tests are used as a screening tool to test aqueous solutions for the presence of certain contaminants. Qualitative tests help to identify the presence (or absence) of an ion or compound in solution (or in air). A colour change is observed if the concentration of the ion or compound is above a specific minimum detection limit. There are no numerical amounts associated with these tests as usually they are “yes/no.”
Semi-quantitative tests are similar to qualitative tests in that they identify the presence of an ion or compound in solution (or air). Where these tests differ is that they provide parts per million (ppm) reading of the ion or compound relative to a blank 0 ppm. A reference colour chart is supplied with the test allowing for easy matching of the test colour to each ppm interval.
Both qualitative and semi-quantitive tests are generally free of significant interference as the chemistry of each test has been designed to eliminate such interferences.