An analysis of Froehde’s and Duquenois-Levine colorimetric tests

Colorimetric testing is frequently used to identify unknown substances in the field. These tests are composed of a solution which changes colors in the presence of certain drugs. Each solution can yield a variety of colors to test compounds, but the tests are nonspecific. The speed of colorimetric analysis has made it ideal for onsite preliminary drug tests. In particular, the Froehde’s solution can identify various opiates and hallucinogens; and the Duquenois-Levine test can identify cannabinoids. Our analysis revealed that the Froehde’s test yields results beyond what is stated in the literature, but that these results are not very specific. The Duquenois-Levine test yields a number of different results, but its criteria for a positive result keep it a more specific test.