Method development and validation for optimized separation of benzo[a]pyrene–quinone isomers using liquid chromatography–mass spectrometry and chemometric response surface methodology

The successful separation of three benzo[a]pyrene–quinone isomers, two of which were previously unresolved, using liquid chromatography–mass spectrometry (LC–MS) and response surface methodology is presented. Initial efforts centered on chromatographic separation of benzo[a]pyrene-1,6/3,6–quinone peaks evaluated for both resolution and retention time. The mergence of the two parameters was accomplished using the Derringer's desirability function with subsequent optimization by a Box–Behnken response surface design. By implementing the optimal flow rate, column temperature and eluent composition predicted by the validated model, enhanced resolution of the two isomers was achieved in less than 20 min. Calibrations were performed to quantify these isomers and the limits of detection were determined. Optimal model conditions were then used to identify three independent benzo[a]pyrene–quinone isomers produced in the irradiation of a benzo[a]pyrene standard solvated in oxygen-saturated methanol/methylene chloride. This work is not only highly significant to the field of environmental chemistry, but instructive for investigators struggling with the co-elusion of isomeric compounds in their work.