Analysis of dioxins by gas chromatography/resonance-enhanced multiphoton ionization/mass spectrometry using nanosecond and picosecond lasers

Adan Li, Tomohiro Uchimura, Yuka Watanabe-Ezoe, Totaro Imasaka

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Abstract

Dioxins in a soil sample were measured using gas chromatography/resonance- enhanced multiphoton ionization/time-of-flight mass spectrometry coupled with different types of laser sources. The fourth-harmonic emission (266 nm) of a nanosecond Nd:YAG laser (1 ns) provided low ionization efficiency, especially for highly chlorinated dioxins/dibenzofurans (CDDs/CDFs). The ionization efficiency was improved using the fourth-harmonic emission (266 nm) of a picosecond Nd:YAG laser (4 ps), due to shorter singlet excited-state lifetimes. It was, however, difficult to efficiently ionize hepta-CDD and octa-CDD/CDF, because of their shorter lifetimes, which were induced by stronger spin-orbit coupling that led to efficient relaxation of the excited molecule to triplet levels. The ionization efficiency was substantially improved using the fifth-harmonic emission (213 nm) of the picosecond Nd:YAG laser (4 ps), in which the analyte molecule that was relaxed to triplet levels was efficiently ionized using a photon with sufficient energy for ionization, although the pulse energy obtained at 213 nm was only one-third of the pulse energy obtained at 266 nm. The limits of detection achieved for 17 toxic polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDDs/PCDFs) were 0.41-45 pg. The analytical instrument developed in the present study performed sufficiently well for the practical trace analysis of dioxins in soil samples.

Original languageEnglish
Pages (from-to)60-66
Number of pages7
JournalAnalytical chemistry
Volume83
Issue number1
DOIs
Publication statusPublished - Jan 1 2011

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All Science Journal Classification (ASJC) codes

  • Analytical Chemistry

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