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>water sample pretreatment because it has many
obvious advantages compared with LLE, such as high
recovery, high pre-concentration factors, low consumption
of organic solvents, simplicity, ease of automation
and operation, and so on [16–17].
Correspondence: Dr. Ru-Song Zhao, Key Laboratory for Applied
Technology of Sophisticated Analytical Instruments of Shandong
Province, Analysis and Test Center, Shandong Academy of
Sciences, Jinan 250014, China
E-mail: zhaors1976@126.com
Fax: +86-531-82964889
Abbreviations: DLLME, dispersive liquid– liquid microextraction;
MWNTs, multiwalled carbon nanotubes
i 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.jss-journal.com
2 R.-S. Zhao et al. J. Sep. Sci. 2009, 32, 0000 – 0000
Recently, dispersive liquid–liquid microextraction
was developed as a fast, simple, and inexpensive solventminimized
liquid–liquid extraction (LLE) technique by
Assadi and his co-workers [18,19]. This technique has
advantages such as rapidity, high enrichment factor,
simplicity of operation, and low cost. The whole process
is as follows [19]: A cloudy solution is formed when an
appropriate mixture of extraction and disperser solvents
is injected into an aqueous sample containing the analytes
of interest; then the hydrophobic solutes are enriched
in the extraction solvent, which is dispersed into the
bulk aqueous solution; after centrifugation, determination
of the analytes in the settled phase can be performed
by conventional analytical techniques. As a novel and
green microextraction technique, dispersive liquid–
liquid microextraction (DLLME), has been successfully
used for the determination of polycyclic aromatic hydrocarbons,
organophosphorus pesticides, chlorobenzenes,
trihalomethanes, and organophosphorus flame retardants
[18–22], and favorable results were obtained. Combination
of SPE and DLLME as a novel sample pretreatment
method has been used successfully for the determination
of phenols in water samples [23].
In this paper, SPE combined with DLLME as a sample
preparation technique with high enrichment factors has
been developed for the sensitive determination of amide
herbicides in water samples. In SPE–DLLME, amide herbicides
were adsorbed quantitatively from a large volume
of aqueous samples (100 mL) onto 100 mg of multiwalled
carbon nanotubes (MWNTs) adsorbent. After elution of
the target compounds from the adsorbent with acetone,
the DLLME technique was performed on the resulting solution.
Finally, the analytes in the extraction solvent were
determined by GC–MS. https://www.51lunwen.org/EnviromentalEngineering/2012/0307/1345144106.html  The influence of different experimental
conditions on the extraction of amide herbicides
from drinking water was studied and the conditions optimized.
Under optimumconditions, high enrichment factors
were achieved in less than 10 min.
2 Experimental
2.1 Reagents and materials

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