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Issue 3, 2002
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Rapid, ultra-sensitive detection of gas phase elemental mercury under atmospheric conditions using sequential two-photon laser induced fluorescence

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Abstract

We have examined the sensitivity of sequential two photon laser induced fluorescence (LIF) detection of elemental mercury, Hg(0) in the gas phase. The most sensitive approach involves an initial laser excitation of the 63P1–61S0 transition at 253.7 nm, followed by excitation with a second laser to the 71S0 level. Blue shifted fluorescence is observed on the 61P1–61S0 transition at 184.9 nm. The excitation scheme, involving sequential excitation of two atomic transitions, followed by detection of the emission from a third is extremely specific and precludes detection of anything other than atomic mercury. Using our 10 Hz laser system we have achieved a detection sensitivity of 0.1 ng m−3 at a sampling rate of 0.1 Hz, i.e. averaging 100 laser shots at a pressure of one atmosphere in air. At low concentrations we sampled simultaneously with an automated mercury analyzer (Tekran 2537A), to ensure accuracy. We have examined the linearity of the technique, generating flows containing mercury concentrations between 1 and 10000 ng m−3 using a permeation tube and dynamic dilution, but relying on the concentrations given by the Tekran at low levels and the concentration calculated from dilution at high levels. We find that the detection is linear over the five orders of magnitude that we were able to vary the concentration. Our measured detection limits in He and Ar are much lower as these gases are inefficient fluorescence quenchers.

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Publication details

The article was received on 03 Jan 2002, accepted on 08 Mar 2002 and first published on 09 Apr 2002


Article type: Paper
DOI: 10.1039/B111688F
Citation: J. Environ. Monit., 2002,4, 339-343
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    Rapid, ultra-sensitive detection of gas phase elemental mercury under atmospheric conditions using sequential two-photon laser induced fluorescence

    D. Bauer, P. Campuzano-Jost and A. J. Hynes, J. Environ. Monit., 2002, 4, 339
    DOI: 10.1039/B111688F

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