Direct Analysis in Real Time (DART) ionization in a novel direct ionization process that occurs at atmospheric pressure. The primary benefit of this technique is that DART can ionize nearly any compound in any state within seconds. Ionization of compounds of interest is achieved through a soft ionization transfer with the metastable ionization species, as long as the excitation potential of the metastable is greater that the ionization potential of the target compound.<br/><br/>This study intends to understand how the DART metastable species interact with different chemical structures during the ionization process. By manipulating the exit grid voltage and ionization temperature of the ionization source, we will determine how the ionization source interacts with different compound types (aliphatic, aromatic, and nitrated). The ultimate goal is to identify which combined set of parameters can overcome competitive ionization processes when analyzing mixtures, in order to target a specific compound type to increase its abundance during analysis.<br/><br/>Initially, an appropriate introduction method that provided reproducible sample introduction to the ionization stream was identified. Each parameter was adjusted and concentration curve samples were analyzed at each method iteration. The first parameter evaluated was the exit grid voltage, in order to determine how this the sample ionizes at increasing positive or negative values with the concentration increase. It was determined that the different exit grid voltages are needed to increase the ionization of specific compounds. The DART calibration curves for each method iteration were compared against a standard concentration curve generated by gas chromatography-mass spectrometry to determine how much deviation occurred. Once a specific ionization process was identified that preferentially targeted one compound type, a 1:1:1 ratio mixture was analyzed using each associated parameter combination to verify targeted ionization occurred.

Targeted DART ionization for rapid analytical screening

2019 Spring National Meeting

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