Session: Analytical Division Student Poster Session: Celebrating the Research of Minority Undergraduate and Graduate Students:

There are an estimated 22,800 backlogged cases dealing with fire debris and explosives awaiting forensic analysis across the United States. A forensic analysis kit that could be deployed to the scene of a crime would be of great value to investigators in such crimes. Many explosive chemicals exhibit luminescence quenching, giving rise to one potential avenue for developing a field-deployable kit. If the kit employed electrochemiluminescence (ECL), it would be far less expensive than one that uses fluorescence, making the kit affordable by municipal law enforcement. For such a kit to be effective, multiple luminescors would need to be utilized in order to distinguish among various explosives, but many known substances that exhibit ECL require non-aqueous solvents, most of which are hazardous. This barrier can be overcome with the use of surfactants to solubilize luminescors. For rapid screening of surfactant/luminescor combinations, 96-well plates were used in a fluorescence plate reader, with the intention of expanding to study ECL once optimum parameters have been established. UV-Vis of standard rubrene solutions in toluene was used to create a calibration curve to provide an estimate of maximum solubility of rubrene in TX-100 of varying concentrations above the CMC: 0.025%, 0.05%, 0.1% and 0.5%. Using those estimated values, rubrene/TX-100 solutions were studied using a fluorescence plate reader to provide a more accurate value for maximum solubility of rubrene; it was found that 0.5% TX100 provided the best results, with a rubrene solubility of 0.045mg/mL. To a set of rubrene/TX100 solutions of constant concentration, increasing amounts of TNT were added, followed by fluorescence analysis and calculation of the quenching factor (QF) for each solution. A plot of QF vs. TNT concentration yields the Stern Volmer constant (K_sv) as the slope. Theoretically, the K_sv should be unique to each luminescor/explosive pair. Similar studies have been conducted with luminol and TNT, and the results from those studies and several other luminescor/explosive pairs will be reported.

Karl Sienerth

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