Trace determination of some aromatic molecules by laser two-photon ionization

A simplified yet sensitiive system is described for the detection of the two-photon ionization signal in solution. The photo-ionization cell consists of a quartz cuvette and a pair of stainless steel electrodes. Several aromatic compounds, including quinones, can be detected in the ng l^?1–mg l^?1 range both in hexane and in methanol; detection limits of pyrene in hexane and in methanol are 0.02 μg l^?1 and 4 μg l^?1, respectively. The detectability in hexane is much better than that in methanol. The detection limits and the molar absorptivities at the excitation wavelength are shown to be correlated.