Despite increased interest in microplasma-induced
vapor generation
(μPIVG) over the past several years, applications in real sample
analyses remain limited due to their relatively low vapor generation
efficiency and ambiguous mechanism. In this work, a novel method using
methanol for significantly enhancing the liquid electrode discharge
μPIVG efficiency was developed for the simultaneous and sensitive
determination of Hg, Cd, and Zn by atomic fluorescence spectrometry
(AFS). It is worth noting that the possible enhancement mechanism
was investigated via the characterizations of volatile
products by AFS, microplasma optical emission spectrometry, online
gas chromatography, and gas chromatography–mass spectrometry,
which involved the reductive species such as electrons, hydrogen radicals
(·H), methyl radicals (·CH3), and other intermediates
in the argon plasma adding methanol. Under the optimized conditions,
the limits of detection of 0.007, 0.05, and 0.5 μg L–1 were obtained for Hg, Cd, and Zn, respectively, with relative standard
deviations of 3.1, 3.7, and 5.2% for these elements, respectively.
Vapor generation efficiencies of 90, 83, and 55% were achieved for
Hg, Cd, and Zn, respectively, and improved 2.7-, 4.8-, and 7.9-fold,
respectively, compared to those obtained in the absence of methanol.
The accuracy and practicability of the proposed method were validated
by the determination of Hg, Cd, and Zn in a certified reference material
(CRM, Lobster hepatopancreas, TORT-3) and crayfish samples collected
from three different provinces of China.