Epc. Lai et al., SPECIATION OF MERCURY AT NG ML CONCENTRATION LEVELS BY CAPILLARY ELECTROPHORESIS WITH AMPEROMETRIC DETECTION/, Analytica chimica acta, 364(1-3), 1998, pp. 63-74
A technique based on capillary electrophoresis and amperometric detect
ion (CE-AD) has been developed for the speciation of mercury. This tec
hnique has the unique capability to detect only cationic mercury speci
es that are electrochemically active. Capillary electrophoresis with e
lectrokinetic injection allows efficient separation of inorganic mercu
ry and organomercury cations in 8 min. Selective detection of these el
ectrochemically active species is attained by controlling the reductio
n potential applied on the micro-electrode. For Hg2+, an optimal poten
tial of -0.2 V can be used to prevent interference by less electroacti
ve toxic metals and other substances found in complex environmental sa
mples. The amperometric signal is linearly proportional to the Hg2+ co
ncentration over three orders of magnitude, with a detection limit of
0.2 ng/ml. The mass detection limit corresponds to 8 fg of Hg2+ in an
injection volume of 40 nl. For CH3Hg+, the detection limit is 3 ng/ml
when a potential of -0.5 V is used. These detection sensitivities are
attractive for environmental monitoring of contaminated sediments in e
cosystems. Steam distillation is evaluated for the extraction of CH3Hg
+ from the sediment matrix. It yields an unknown mercury species which
is unsuitable for CE-AD determination under the specified conditions.
(C) 1998 Elsevier Science B.V.