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1Key laboratory for AppliedTechnology of SophisticatedAnalytical Instruments ofShandong province, Analysisand Test Center, ShandongAcademy of Sciences, Jinan,China
2Shandong Key Lab of Eco-Environmental Science forYellow River Delta, BinzhouUniversity, Binzhou, China
Original Paper
Sensitive determination of amide herbicides in environmental water samples by a combination of solid-phase extraction and dispersive liquid–liquid microextraction prior to GC–MS
In this paper, solid-phase extraction in combination with dispersive liquid –liquid
microextraction (DLLME) has been developed as a sample pretreatment methodwith high enrichment factors for the sensitive determination of amide herbicides in
water samples. In SPE–DLLME, amide herbicides were adsorbed quantitatively froma large volume of aqueous samples (100 mL) onto a multiwalled carbon nanotubeadsorbent (100 mg). After elution of the target compounds from the adsorbent withacetone, the DLLME technique was performed on the resulting solution. Finally, the
analytes in the extraction solvent were determined by gas chromatography–massspectrometry. Some important extraction parameters, such as flow rate of sample,
breakthrough volume, sample pH, type and volume of the elution solvent, as well assalt addition, were studied and optimized in detail. Under optimum conditions,high enrichment factors ranging from 6593 to 7873 were achieved in less than10 min. There was linearity over the range of 0.01–10 lg/L with relative standarddeviations of 2.6–8.7%. The limits of detection ranged from 0.002 to 0.006 lg/L. The
proposed method was used for the analysis of water samples, and satisfactory results
were achieved.
Keywords: Amide herbicides / Dispersive liquid– liquid microextraction / Gas chromatography–mass spectrometry / Solid-phase extraction /

1 Introduction
Herbicides provide great benefits for increasing agricultural
production; however, their residues in crops, soils,
and waters are of great concern [1]. Among the various
herbicides available, the amide herbicides acetochlor,
butachlor, and metolachlor are the ones most widely
used in China (Fig. 1) [2, 3]. For acetochlor, butachlor,
and metolachlor, yearly production in China amounts to
20, 0.6, and 7 million kg, respectively [4]. The World
Health Organization has assigned a hazard ranking of III
(slightly hazardous) for acetochlor and metolachlor and
a ranking of U (unlikely to be hazardous) for butachlor
[5]. The United States Environmental Protection Agency
(USEPA) has established a maximum residue level of acetochlor
in groundwater of 0.1 lg/L [6]. Hence, rapid, simple,
and sensitive methods are necessary for monitoring
the widespread distribution of these herbicides.
Direct determination of these herbicides is often difficult
because of the complexity of the environmental
matrix and the low concentration of target compounds.
Many sample pretreatment procedures have been developed
for their separation and preconcentration, such as
liquid –liquid extraction lLLE) [7,8], solid-phase extraction
[9–11], single-drop microextraction (SDME) [12], and
solid phase microextraction (SPME) procedures [13–15].
SPE reduces the quantity of solvent used and simplifies
the sample preparation step. Among the above mentioned
sample pretreatment techniques, solid-phase
extraction is the most common technique for environmental本论文由英语论文网提供整理，提供论文代写，英语论文代写，代写论文，代写英语论文，代写留学生论文，代写英文论文，留学生论文代写相关核心关键词搜索。