Evaluation and application of argon and helium microstrip plasma for the determination of mercury by the cold vapor technique and optical emission spectrometry |
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Authors: | Israel Jiménez Zapata Pawel Pohl Nicolas H Bings José A C Broekaert |
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Institution: | (1) Institute for Inorganic and Applied Chemistry, Department of Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany |
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Abstract: | The suitability of a 2.45-GHz atmospheric pressure, low-power microwave microstrip plasma (MSP) operated with Ar and He for
the determination of Hg by continuous-flow cold vapor (CV) generation, using SnCl2/HCl as the reducing agent, and optical emission spectrometry (OES) using a small CCD spectrometer was studied. The areas
of stability for a discharge in the Ar and in the He MSP enclosed in a cylindrical channel in a quartz wafer were investigated.
The excitation temperatures as measured for discharge gas atoms (Ar I, He I), and the electron number densities at 35–40 W
and 15–400 mL min−1 were found to be at the order of 3,200–5,500 K and 0.8 × 1014–1.6 × 1014 cm−3, respectively. The relative intensity of the Hg I 253.6-nm line and the signal-to-background ratio as a function of the forward
power (35–40 W) as well as of the flow rate of the working gas (15–400 mL min−1) were evaluated and discussed. For the selected measurement conditions, the Ar MSP was established to have the lower detection
limit for Hg (0.6 ng mL−1) compared with the He MSP. The linearity range is up to 300 ng mL−1 and the precision is on the order of 1–3%. With the optimized CV Ar MSP-OES method a determination of Hg in spiked domestic
and natural waters at concentration levels of 20–100 μg L−1 and an accuracy of 1–4% could be performed. In an NIST domestic sludge standard reference material, Hg (3.64 μg g−1) could be determined with a relative standard deviation of 4% and an agreement better than 4%. |
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Keywords: | Microwave microstrip plasma Cold vapor generation Mercury Optical emission spectrometry |
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