Postblast and Postburn Identification of Forensically Relevant Nitrate Salts as Crown Ether Complexes by Paper Spray...

Ammonium nitrate, along with metal nitrates (including alkali and alkaline earth metal nitrates), is a key oxidizing agent studied in postblast forensics because it is frequently used in explosive mixtures. Herein, the use of crown ether additives in paper spray ionization to form complexes containing a nitrate salt of interest is demonstrated. The resulting ionic complex can then be isolated and fragmented to generate structurally informative product ions. This allows for the detection of the cation of interest (e.g., ammonium, barium, potassium) and nitrate from a sample in one mass spectrum. Postblast and postburn samples analyzed during method development demonstrated that the analytical figures of merit for this methodology are adequate for use in a forensic setting for identification. Specifically for ammonium nitrate, the lower limit of detection was found to be approximately 40 μg mL^-1 and an upper limit of detection of 4.9 × 10³ μg mL^-1 was also determined. Barium nitrate and potassium nitrate complexations showed similar limits of detection as ammonium nitrate (80 and 65 μg mL^-1, respectively).