Analytical Sciences

Analysis of Persistent Organic Pollutants at Sub-Femtogram Levels Using a High-Power Picosecond Laser for Multiphoton Ionization in Conjunction with Gas Chromatography/Time-of-Flight Mass Spectrometry

Taiki MATSUI,* Kodai FUKAZAWA,** Masatoshi FUJIMOTO,** and Totaro IMASAKA*,***

*Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
**Business Promotion Project, Hamamatsu Photonics K. K., 5000 Hirakuchi, Hamakita, Hamamatsu, Shizuoka 434-8601, Japan
***Division of Translational Research, Center for Future Chemistry, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan

A low-energy, high-repetition-rate picosecond laser (40 μJ, 20 kHz, 258 nm) was used for multiphoton ionization (MPI) in gas chromatography/time-of-flight mass spectrometry to quantitatively determine dioxins (DXNs) and polycyclic aromatic hydrocarbons (PAHs). The sensitivity of the technique was compared with that obtained using a high-energy, low-repetition-rate femtosecond laser (86 μJ, 1 kHz, 261 nm). The limits of detection (LODs) for the picosecond laser were several femtograms for chlorinated DXNs with low numbers of chloro substituents, and were several times lower than values obtained using a femtosecond laser, although the LODs were increased, reaching values that were nearly identical to those for the femtosecond laser for octachlorodibenzo-p-dioxin (octaCDD) and octachlorodibenzofuran (octaCDF). The LODs were also measured for 16 PAHs specified by the United States Environmental Protection Agency; the values for half of these compounds were at sub-femtogram levels. The procedure was used to analyze a surface-water sample collected from a river.

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