MEASUREMENT OF MERCURY METHYLATION IN SEDIMENTS BY USING ENRICHED STABLE MERCURY ISOTOPES COMBINED WITH METHYLMERCURY DETERMINATION BY GAS-CHROMATOGRAPHY INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY
H. Hintelmann et al., MEASUREMENT OF MERCURY METHYLATION IN SEDIMENTS BY USING ENRICHED STABLE MERCURY ISOTOPES COMBINED WITH METHYLMERCURY DETERMINATION BY GAS-CHROMATOGRAPHY INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY, Journal of analytical atomic spectrometry, 10(9), 1995, pp. 619-624
A novel technique for the calculation of mercury methylation rates in
sediments by using enriched stable mercury isotopes is described. The
method takes advantages of the ability of an inductively coupled plasm
a mass spectrometry (ICP-MS) instrument to measure individual isotopes
. An ICP-MS instrument was used as a detector for the determination of
methylmercury compounds after separation by gas chromatography (GC),
CH3Hg+ was isolated from sediments by distillation, converted to methy
lethylmercury by sodium tetraethylborate and analysed after purge-and-
trap precollection on a Tenax adsorber and thermodesorption onto the G
C column. Detection limits were found to be approximate to 1 pg (as Hg
) absolute or 0.02 ng g(-1) dry sediment. The precision was approximat
e to 4% relative standard deviation when 250 pg of methylmercury were
processed. The accuracy of the GC-ICP-MS technique was demonstrated by
analysis of an International Atomic Energy Agency certified reference
material (IAEA CRM 356) Harbor Sediment, giving a concentration of 5.
40 +/- 0.40 ng g(-1), compared with the certified value of 5.46 +/- 0.
38 ng g(-1) Mercury methylation was investigated by spiking sediments
with stable enriched mercury isotopes at in situ mercury concentration
s not perturbing the system. More than 3% of the mercury added to a la
ke sediment was methylated during a 21 d incubation period. Isotope ra
tios of total mercury differed significantly from isotope ratios of me
thylmercury at the end of the experiment, suggesting that the system w
as still not in equilibrium after 21 d.