Development of a field kit for use by non-scientists for chemical tracking using 5-(4-nitrophenyl)-2,4-pentadien-1-al

5-(4-Nitrophenyl)-2,4-pentadien-1-al (NPPD) can be used for chemical tracking in crime scene investigations. A color test kit for NPPD was developed for use by non-scientists, such as police officers, in the field. However, this kit had problems, including contact with concentrated HCl, and instability of the reagent (naphthoresorcinol methanol solution) used in the first step of color development. To overcome these problems, in the present study, a field kit was developed with the concentrated HCl sealed in a vial so it did not contact the operator. A glass tube with two compartments was used to separate the naphthoresorcinol and methanol before use. When the color test was conducted, a cotton swab was inserted into the tube. Before insertion, the cotton was used to collect a sample from a suspect that had been in contact with a surface sprayed with a 1% NPPD methanol solution. Insertion of the cotton swab broke the thin glass that separated the methanol and naphthoresorcinol, and any NPPD on the swab reacted with the naphthoresorcinol methanol solution. The cotton swab was then pushed further to break the glass separating the concentrated HCl. A red color then developed if NPPD was present on the cotton swab. For testing the kit, NPPD was sprayed in an area where a crime was expected to occur. This kit will be useful for detecting a contact with or near a crime scene, because samples do not require analysis in a forensic science laboratory. Instead, the results can be confirmed at the scene of crime.