Determination of total mercury and methylmercury in biological samples by photochemical vapor generation |
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Authors: | Mariana A Vieira Anderson S Ribeiro Adilson J Curtius Ralph E Sturgeon |
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Institution: | (1) Departamento de Química, Universidade Federal de Santa Catarina, Florianópolis, SC, 88040 900, Brazil;(2) Institute for National Measurement Standards, National Research Council Canada, Ottawa, ON, K1A 0R9, Canada |
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Abstract: | Cold vapor atomic absorption spectrometry (CV-AAS) based on photochemical reduction by exposure to UV radiation is described
for the determination of methylmercury and total mercury in biological samples. Two approaches were investigated: (a) tissues
were digested in either formic acid or tetramethylammonium hydroxide (TMAH), and total mercury was determined following reduction
of both species by exposure of the solution to UV irradiation; (b) tissues were solubilized in TMAH, diluted to a final concentration
of 0.125% m/v TMAH by addition of 10% v/v acetic acid and CH3Hg+ was selectively quantitated, or the initial digests were diluted to 0.125% m/v TMAH by addition of deionized water, adjusted
to pH 0.3 by addition of HCl and CH3Hg+ was selectively quantitated. For each case, the optimum conditions for photochemical vapor generation (photo-CVG) were investigated.
The photochemical reduction efficiency was estimated to be ∼95% by comparing the response with traditional SnCl2 chemical reduction. The method was validated by analysis of several biological Certified Reference Materials, DORM-1, DORM-2,
DOLT-2 and DOLT-3, using calibration against aqueous solutions of Hg2+; results showed good agreement with the certified values for total and methylmercury in all cases. Limits of detection of
6 ng/g for total mercury using formic acid, 8 ng/g for total mercury and 10 ng/g for methylmercury using TMAH were obtained.
The proposed methodology is sensitive, simple and inexpensive, and promotes “green” chemistry. The potential for application
to other sample types and analytes is evident. |
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Keywords: | Mercury Methylmercury Speciation Photochemical reduction Vapor generation Formic acid Tetramethylammonium hydroxide |
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