Limitations of Simon test in new psychoactive substances analysis

New psychoactive substances (NPS) are nowadays a prevalent group of illicit drugs, one of which are synthetic cathinones. The widespread usage of NPS requires fast, reliable, selective and sensitive analytical methods for their identification as well as differentiation. Colorimetric tests are among the most frequently used methods for screening analysis of NPS in forensic sciences because they are fast, cheap and simple they found application in roadside, borders and airport controls, as well as are used for employees control at workplaces. In this paper we present limitations of colorimetric tests based on the example of one of the Simon test’s variant which was used to analyze synthetic cathinones samples. 163 seized drugs samples were analyzed. Used variant of the Simon test comprises reaction of secondary amines with sodium nitroprusside, sodium carbonate and acetaldehyde resulting in deep blue coloration. Our study indicated that the test gives a very low positive results percentage (3%), as well as many false negative results (88%). No pattern in color changes could be observed regarding samples belonging to one group of compounds in order to identify it even when lacking the expected observation. Another important aspects regarding colorimetric test is the fact that observations are very subjective. although this method is fast and easy to perform, it does not provide unambiguous results and thus, they always should be confirmed with the use of other analytical techniques such as LC-MS/MS or GC-MS/MS.