Analysis of oxidizer salt mixtures by electrospray ionization mass spectrometry

On-site rapid detection of trace non-volatile inorganic explosives by stand-alone ion mobility spectrometry via acid-enhanced evaporization

New techniques for the field detection of inorganic improvised explosive devices (IEDs) are urgently developed. Although ion mobility spectrometry (IMS) has been proved to be the most effective method for screening organic explosives, it still faces a major challenge to detect inorganic explosives owing to their low volatilities. Herein, we proposed a strategy for detecting trace inorganic explosives by thermal desorption ion mobility spectrometry (TD-IMS) with sample-to-sample analysis time less than 5 s based on in-situ acidification on the sampling swabs. The responses for typical oxidizers in inorganic explosives, such as KNO3, KClO3 and KClO4 were at least enhanced by a factor of 3000 and their limits of detection were found to be subnanogram. The common organic explosives and their mixtures with inorganic oxidizers were detected, indicating that the acidification process did not affect the detection of organic explosives. Moreover, the typical inorganic explosives such as black powders, firecrackers and match head could be sensitively detected as well. These results demonstrated that this method could be easily employed in the current deployed IMS for on-site sensitive detection of either inorganic explosives or organic ones.

Analysis of ascorbic acid based black powder substitutes by high-performance liquid chromatography/electrospray ionization quadrupole time-of-flight mass spectrometry

Black powder substitutes are an important sub-group of explosive propellants in the United States because they are readily accessible, and can be used as fillers for improvised explosive devices. Many brands of black powder substitutes incorporate an ascorbic acid fuel source with potassium nitrate (KNO(3)) and/or potassium perchlorate (KClO(4)) oxidizer(s). A gradient high-performance liquid chromatography/electrospray ionization quadrupole time-of-flight mass spectrometry (HPLC/ESI-QToFMS) method has been developed for the analysis of both the organic and the inorganic constituents. The HPLC/ESI-QToFMS method was utilized to examine aqueous extracts of intact samples and post-burn residues from six different brands of ascorbic acid based powders. Aqueous extracts of the post-blast residues from two brands of ascorbic acid based propellant were also analyzed. The results showed that both the ascorbic acid fuel and the inorganic oxidizer(s) KClO(4) and/or KNO(3) were successfully detected via the [M-H](-) ion of ascorbic acid and the anions (ClO(4) (-) and NO(3) (-)) of the oxidizers. This method was proven to be a rapid and efficient procedure for the analysis of this class of explosives. The high mass resolution provided by the QToFMS instrument fulfills the degree of certainty required in a court of law.