Paper AS+BI+IS-WeM6
Comparison of Ambient Pressure Ionization Sources by Determining Useful Yields of Forensic Compounds of Interest

Wednesday, October 30, 2013, 9:40 am, Room 204

The detection of illicit drugs and trace explosives represents one of the most significant challenges for law enforcement and forensic communities. Of particular interest to the forensic analyst is the ability to rapidly identify suspected illicit drug materials and explosives residues in their native state (powder, tablet or liquid form), under atmospheric conditions and with a high level of specificity and sensitivity. To that end there are numerous ambient pressure ionization techniques such as atmospheric pressure glow discharge (APGD), low temperature plasma (LTP), and desorption electrospray ionization (DESI) that can be used to interrogate forensic compounds. However, a method of comparing between the different ambient ionization sources does not exist. Here, useful yields are determined for a series of forensic compounds using different ambient pressure ionization sources as a means of comparison. Using a precision inkjet deposition system a well-defined array of microdrops is produced with each deposit containing a known number of analyte molecules. The individual deposits were removed or desorbed until consumed while monitoring the integrated characteristic molecular secondary ions for each analyte. The ratio of integrated counts to the number of molecules in the deposit defines the useful yield of the experiments. The results here highlight a way to compare the different ambient ionization sources for the analysis of forensic compounds of interest.