Saccharomyces cerevisiae immobilized in agarose gel as binding phase and polyacrylamide as diffusive
layer in the diffusive gradient in thin films technique (DGT) was used for selective determination of
methylmercury (MeHg). Deployment tests showed good linearity in mass uptake up to 48 h (3276 ng).
When coupling the DGT technique with Cold Vapor Atomic Fluorescence Spectrometry, the method has a
limit of detection of 0.44 ng L1 (pre concentration factor of 11 for 48 h deployment). Diffusion coefficient
of 7.03 ± 0.77 106 cm2 s
1 at 23 C in polyacrylamide gel (pH ¼ 5.5 and ionic strength ¼ 0.05 mol L1
NaCl) was obtained. Influence of ionic strength (from 0.0005 mol L1 to 0.1 mol L1 NaCl) and pH (from
3.5 to 8.5) on MeHg uptake were evaluated. For these range, recoveries of 84e105% and 84e98% were
obtained for ionic strength and pH respectively. Potential interference due to presence of Cu, Fe, Mn, Zn
was also assessed showing good recoveries (70e87%). The selectivity of the proposed approach was
tested by deployments in solutions containing MeHg and Hg(II). Results obtained showed recoveries of
102e115 % for MeHg, while the uptake of Hg(II) was insignificant. The proposed approach was successfully
employed for in situ measurements in the Negro River (Manaus-AM, Brazil).
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