Environmental Engineering Reference
In-Depth Information
78.6-105.6%, 87.2-100.7%, 96.5-105.6% and 83.7-11.1%, respectively, which
indicates that the proposed method could be used in a real environmental water sample
analysis. Furthermore, neonicotinoid insecticides (thiamethoxam, imidacloprid, and
acetamiprid) (Zhou et al., 2006a), triazine herbicides (atrazine and simazine) (Zhou et al.,
2006d), and organochlorine pesticides (DDT and its metabolite) (Zhou et al., 2006c)
were well determined by using MWNTs as SPE adsorbents, even in real water samples
such as river water, ground water, reservoir water, tap water, and wastewater.
MWNTs were used as adsorbents for the preconcentration of phthalate esters
(Cai et al., 2003a), endocrine disruptors including bisphenol A, 4-n-nonylphenol and 4-
tert-octylphenol (Cai et al., 2003b), and chlorophenols (Cai et al., 2005) in
environmental water samples before choromatographic analysis; favorable achievements
were obtained for each case.
Munoz et al. (2005) used MWNTs as an SPE adsorbent for the preconcentration
of various organometallic compounds. Before being adsorbed on a MWNT-packed
column, organolead, tin, and mercury compounds were derivatized with sodium
diethyldithiocarbamate. In this case, MWNTs were found to be superior to graphitized
carbon black and RP-C
18
for the extraction of the organometallic compounds studied;
however, no significant differences between C
60
and C
70
fullerenes and MWNTs were
determined (Munoz et al., 2005).
Not only did caged MWNTs exhibit excellent adsorption capabilities for dyes
(Fugetsu et al., 2004b), as mentioned previously, but they also acted as an adsorbent for
the preconcentration/elimination of dibenzo-p-dioxin (DD), dibenzofuran (DF) and
biphenyl (BP) from contaminated water (Fugetsu et al., 2004a). The column packed with
caged MWNTs showed the highest affinity for retaining DD, DF, and BP, which was
due to the strong interactions between the hexagonal arrays of the carbon atoms in the
graphene sheets of MWNTs with the aromatic bonds of the toxic compounds, owing
probably to van der Waals interaction. In addition, the caged MWNT adsorbents could
be reused by washing with hexane or methanol.
CNT as SPME Coating.
To the authors' knowledge, only one report to date has
mentioned a method using MWNTs as an SPME fiber coating. MWNT coated fibers for
the SPME of polybrominated diphenyl ethers (PBDE) in real samples such as local river
water, wastewater, and milk were examined (Wang et al., 2006). Here, the MWNT
coated fiber was prepared by depositing a suspension of MWNT powder dispersed in
dimethylformamide under sonication onto the pretreated fused-silica fiber. Various
parameters of the SPME of PBDEs were studied and optimized, including the extraction
time, magnetic stirring rate, ionic strength, desorption temperature, and desorption time.
Under optimized conditions, MWNT coated fibers were more effective for the SPME of
PBDEs than activated carbon and polydimethylsiloxane-dibenzene (95% PDMS-5%
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