Online mercury determination by laser-induced
breakdown spectroscopy with the assistance of
solution cathode glow discharge
Peichao Zheng,
*
Hongdi Liu, Jinmei Wang, Minjie Shi, Xiaomeng Wang, Bin Zhang
and Rui Yang
The trace mercury in an aqueous solution was determined by laser-induced breakdown spectroscopy (LIBS)
with the assistance of a solution cathode glow discharge (SCGD) system. The aqueous solution was
converted to the gas phase using a high voltage DC discharge, and then the generated mercury vapor
was cooled by a gas–liquid separator to improve the concentration of the mercury. Finally, a 1064 nm
wavelength Nd:YAG laser was used to produce the plasma. In the present experiment, the characteristic
spectral line of Hg
I 253.65 nm was selected for the analysis, under the optimal conditions of LIBS, to
investigate the influences of the acid anion, the discharge current, the sample flow rate and the carrier
gas flow rate. The temporal behavior of the electron temperature and electron number density were also
investigated; the results show that the electron temperature decreases from about 10 900 K to 8800 K
with a delay time from 200 ns to 6 ms and that the electron number density is in the orders of 10
17
and
10
18
cm
3
, and decreases with delay time. The analytical performance of this method was evaluated
under optimized conditions, and a calibration curve of Hg was plotted based on the different
concentrations measurement results, and the detection limit (LOD) of Hg was calculated to be 0.36 mg L
1
.
By this experimental configuration, the detection limit and sensitivity of Hg are improved to some extent. This
method provides an alternative analytical method for the measurement of trace mercury in water.
Introduction
Nowadays, environmental pollution problems are seen as being
more and more serious, with heavy metal pollution being a
particular concern. Various heavy metal pollution releases from
industry, transport, and domestic waste have had a serious
inuence on environmental and human health.
1
Mercury is one
of the most toxic and hazardous of elements, and problems
arise as it is durable, easy to transport, and can have a high
biological enrichment, where any form of mercury can be con-
verted into toxic methyl–mercury under certain conditions.
Thus, mercury is considered a global pollutant, due to its long
residence time, and as a major concern as mercury pollution
has greatly increased in recent years. As a naturally occurring
element, mercury can be found throughout the environment
(soil, water, air) where it exists in three forms: elemental or
metallic, inorganic, and organic.
2
Due to the characteristics
mentioned above, there is an increasing concern about the
determination and monitoring of mercury. Strict regulations of
the maximum allowable mercury concentration in the
environment and food samples have been established
throughout the world, but effective detecting methods are in
urgent demand for the corresponding supervisory departments
who have to monitor mercury.
In the past several decades, many detection methods have
been proposed for the determination of mercury, and much
effort has been devoted to improving the limit of detection
(LOD) of mercury, because this element is usually present in
food and water samples at extremely low concentrations. Hinds
3
developed a procedure to determine mercury in unrened gold
by ame and graphite furnace atomic absorption spectrometry
(AAS). Grotti et al.
4
rened a procedure for the simultaneous
determination of arsenic, selenium, and mercury in foodstuffs
by inductively coupled plasma-optical emission spectroscopy
(ICP-OES). Pyhtil
¨
a et al.
5
developed and optimized a method for
the determination of low total mercury concentrations in
humic-rich natural water samples using a cold vapor technique
coupled to an inductively coupled plasma mass spectrometer
(CV-ICP-MS). Hieje's group
6
developed a novel cold vapor
generation method using solution cathode glow discharge
(SCGD) coupled with ICP-OES in 2008. And then, He et al.
7
used
the novel SCGD induced vapor generation as an interface to on-
line couple high-performance liquid chromatography (HPLC)
with atomic uorescence spectrometry (AFS) for the speciation
of inorganic mercury, methyl–mercury, and ethyl–mercury.
College of Optoelectronic Engineering, Chongqing University of Posts and
Telecommunications, Chongqing Municipal Level Key Laboratory of Photoelectronic
Information Sensing and Transmitting Technology, Chongqing 400065, P. R. China.
E-mail: zhengpc@cqupt.edu.cn; Fax: +86-23-62460592; Tel: +86-23-62460592
Cite this: J. Anal. At. Spectrom.,2015,
30, 867
Received 19th October 2014
Accepted 3rd December 2014
DOI: 10.1039/c4ja00350k
www.rsc.org/jaas
This journal is © The Royal Society of Chemistry 2015 J. Anal. At. Spectrom.,2015,30,867–874 | 867
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