Liquid chromatographic determination of nitro-substituted polynuclear aromatic hydrocarbons by sequential electrochemical and fluorescence detection.

Nitro-substituted polynuclear aromatic hydrocarbons occur in ambient suspended particulate matter and are of special concern because they act as direct mutagens. Determination of these compounds in a complex matrix such as particulate matter present in diesel engine exhaust is complicated [Formula: see text] even mass spectrometry requires initial cleanup and separation steps. We propose a sensitive liquid chromatographic method with an unique selectivity:  an electrochemical detector operating in the reductive mode is followed by a fluorescence detector. When the NO(2) group is reduced to the NH(2) group, there is a major increase in fluorescence; nitro-PAH compounds are essentially nonfluorescent. A difference fluorescence signal or a difference chromatofluorogram is generated by subtracting the chromatogram obtained with the electrochemical detector off from that obtained with the electrochemical detector on. Applications to diesel engine exhaust samples are demonstrated.