Proposed reaction mechanisms for selenium UV photolysis vapor generation by computational methods.

The production of volatile analyte species by UV photolysis in the presence of low-molecular-weight organic acids as an alternative to chemical vapor generation has been of recent interest. The mechanism of this process is not well understood. Proposed mechanisms often involve photolytic cleavage of the organic acid as the initial step. Evidence suggests that this may not be the dominant route for UV photolysis vapor generation. In this work computational methods were applied to determine a possible alternative mechanism in the absence of free-radical production. The proposed mechanism specifically focused on selenium vapor generation. An energetically favored mechanism was found for UV photolysis of inorganic selenium in the presence of formic and acetic acids which is consistent with previously reported experimental results.