Two- and three-wavelength laser multiphoton ionization for highly sensitive detection in solution.
Novel two- and three-wavelength laser multiphoton ionization techniques for highly sensitive detection in solution have been established. The photocurrent signal obtained for benzo[a]pyrene by irradiation at 355 nm in n-heptane was effectively enhanced by additional simultaneous irradiation at 532 and/or 1064 nm. The additional irradiation at 532 nm (5 mJ) doubled the signal-to-noise ratio, while that at 1064 nm (30 mJ) increased it 5.5-fold relative to that obtained when only the 355 nm radiation was used. The simultaneous action of 355, 532 (5 mJ) and 1064 (25 mJ) nm radiation further improved the S/N ratio; the detection limit was as low as 1.9 x 10(-10)M. The 532 nm radiation enhanced the photocurrent signal more effectively than did the 1064 nm radiation.
Yamada
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College of General Education, University, Ropponmatsu 4-2-1, Chuo-ku, Fukuoka 810, Japan.
Shinno
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