外文翻譯--分散固相萃取–分散液液微萃取高效液相色譜法對(duì)土壤中某些磺酰脲類除草劑的測(cè)定（英文）

1、Journal of Chromatography A, 1216 (2009) 5504–5510Contents lists available at ScienceDirectJournal of Chromatography Ajournal homepage: www.elsevier.com/locate/chromaDispersive solid-phase extraction followed by dispersi

2、ve liquid–liquid microextraction for the determination of some sulfonylurea herbicides in soil by high-performance liquid chromatographyQiuhua Wu a, Chun Wang a, Zhimei Liu b, Chunxia Wu a, Xin Zeng b, Jialin Wen c, Zhi

3、Wang a,?a Key Laboratory of Bioinorganic Chemistry, College of Science, Agricultural University of Hebei, Baoding 071001, Hebei, Chinab College of Food Science and Technology, Agricultural University of Hebei, Baoding 07

4、1001, Hebei, Chinac School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, Jiangsu, Chinaa r t i c l e i n f oArticle history:Received 19 February 2009Received in revised form 11 May 2009Accept

5、ed 25 May 2009Available online 3 June 2009Keywords:Sulfonylurea herbicidesHigh-performance liquid chromatographyDispersive solid-phase extractionDispersive liquid–liquid microextractionSoil samplesa b s t r a c tDispersi

6、ve solid-phase extraction (DSPE) combined with dispersive liquid–liquid microextraction(DLLME) has been developed as a new approach for the extraction of four sulfonylurea herbicides(metsulfuron-methyl, chlorsulfuron, be

7、nsulfuron-methyl and chlorimuron-ethyl) in soil prior to high-performance liquid chromatography with diode array detection (HPLC-DAD). In the DSPE-DLLME,sulfonylurea herbicides were first extracted from soil sample into

8、acetone–0.15 mol L?1 NaHCO3 (2:8,v/v). The clean-up of the extract by DSPE was carried out by directly adding C18 sorbent into the extractsolution, followed by shaking and filtration. After the pH of the filtrate was adj

9、usted to 2.0 with 2 mol L?1HCl, 60.0 ?L chlorobenzene (as extraction solvent) was added into 5.0 mL of it for DLLME procedure(the acetone contained in the solution also acted as dispersive solvent). Under the optimum con

10、ditions,the enrichment factors for the compounds were in the range between 102 and 216. The linearity of themethod was in the range from 5.0 to 200 ng g?1 with the correlation coefficients (r) ranging from 0.9967to 0.998

11、7. The method detection limits were 0.5–1.2 ng g?1. The relative standard deviations varied from5.2% to 7.2% (n = 5). The relative recoveries of the four sulfonylurea herbicides from soil samples at spikinglevels of 6.0,

12、 20.0 and 60.0 ng g?1 were in the range between 76.3% and 92.5%. The proposed method hasbeen successfully applied to the analysis of the four target sulfonylurea herbicides in soil samples, and asatisfactory result was o

13、btained.© 2009 Elsevier B.V. All rights reserved.1. IntroductionSulfonylurea herbicides are widely used as selective pre- andpost-emergence herbicides for the control of most broad-leavedweeds and annual grasses in

14、many agricultural crops due to theirlow application rates (in the range of 10–100 g ha?1), low toxicityto mammals and unprecedented herbicidal activity. However, theremaining low concentration residues of these compounds

15、 in soilcan still affect the growth of susceptible plants [1]. So, sensitive andselective analytical methods are desirable for the determination ofsulfonylurea herbicide residues in soil in order to control carry-overfro

16、m one growing season to the next.Sample preparation is one of the most important and cru-cial steps in the whole analytical process. For the determinationof sulfonylurea herbicides, several sample preparation meth-ods ha

17、ve been developed, including solid-phase extraction (SPE)[2–4], supercritical fluid extraction (SFE) [5], microwave-assisted? Corresponding author. Tel.: +86 312 7521513; fax: +86 312 7521513.E-mail address: wangzhi@heba

18、u.edu.cn (Z. Wang).solvent extraction (MASE) [6] and molecularly imprinted SPE[7].In 2006, a novel microextraction technique named dispersiveliquid–liquid microextraction (DLLME) was developed by Assadiand co-workers [8]

19、. DLLME is a miniaturized liquid–liquid extrac-tion (LLE) that uses microliter volumes of the extraction solvent. ForDLLME, water-immiscible extraction solvent dissolved in a water-miscible dispersive solvent is rapidly

20、injected into an aqueoussolution by syringe. A cloudy solution containing fine droplets ofextraction solvent dispered entirely in the aqueous phase is formed.The analytes in the sample are extracted into the fine droplet

21、s,which are further separated by centrifugation, and the enrichedanalytes in the sedimented phase are determined by either chro-matographic or spectrometric methods. The advantages of theDLLME method are short extraction

22、 time, low cost, simplicity ofoperation and high enrichment factor. DLLME has been applied forthe analysis of a variety of trace organic pollutants and metal ionsin environmental samples [9–17].The objective of the sampl

23、e preparation is often not only toisolate the target analytes from the samples and concentrate theanalytes, but also simultaneously to reduce or even eliminate the0021-9673/$ – see front matter © 2009 Elsevier B.V.

24、All rights reserved.doi:10.1016/j.chroma.2009.05.0625506 Q. Wu et al. / J. Chromatogr. A 1216 (2009) 5504–5510Fig. 1. The chromatograms of Xixiaozhuang soil without clean-up by DSPE (A), with clean-up by C18 (B), and cle

25、an-up by MWCNT (C). Monitoring wavelength: 225 nm; thesoil sample was spiked with each sulfonylurea at 30 ng g?1; (1) MSM; (2) CS; (3) BSM; (4) CME.from soil, basic sodium bicarbonate or phosphate aqueous solu-tion (pH f

26、rom 7 to 9.5) was commonly used as extraction solvent[2,28,29]. In our preliminary experiment, methanol–0.15 mol L?1NaHCO3 (2:8, v/v, pH about 8.4) gave a slightly higher extrac-tion recovery than acetone–0.15 mol L?1 Na

27、HCO3 (2:8, v/v) andacetonitrile–0.15 mol L?1 NaHCO3 (2:8, v/v). But for the subsequentDLLME, the extraction recovery of sulfonylurea herbicides wasmuch lower with either methanol or acetonitrile being used as dis-persive

28、 solvent than that with acetone (see Section 3.2.1). Givingan overall consideration of the extraction efficiency of both DSPEand DLLME altogether, acetone–0.15 mol L?1 NaHCO3 (2:8, v/v) wasselected as the extraction solv

29、ent.3.1.2. Optimization of the DSPE sorbentBecause of the presence of the matrix co-extractive interferencesfrom soil samples, DSPE was adopted to clean-up the crude extract.The sorbent for DSPE was optimized through com

30、parison betweenC18 and carbon nanotubes. Fig. 1 shows the chromatograms of Xix-iaozhuang soil obtained without clean-up by DSPE, with clean-upeither by C18 or by MWCNT. The results indicate that both carbonnanotubes and

31、C18 could give a good clean-up effect, but comparedwith the result with C18, the recoveries for both BSM and CME weredecreased when carbon nanotubes were used. After further opti-mization, 0.15 g C18 per 10 mL extract wa

32、s selected as the DSPEsorbent.3.2. Optimization of the DLLME procedureIn order to economize the time of optimizing the DLLME proce-dure, 5.0 mL double-distilled water spiked with 100 ng mL?1 eachof the four sulfonylurea

33、herbicides was used to study the extractionperformance of the DLLME under different experimental condi-tions. All experiments were performed in triplicate and the meansof the results were used for optimization. The enric

34、hment factor(EF) and extraction recovery (R) were calculated according to theequations described in Refs. [8–10] as follows:EF = CsedC0 (1)where EF, Csed and C0 are the enrichment factor, the analyte con-centration in th

35、e sediment and the initial analyte concentration inthe aqueous samples, respectively.R% = CsedVsedC0Vaq × 100 (2)where R%, Vsed and Vaq are the extraction recovery, the volume ofthe sediment phase and the volume of

36、the aqueous sample, respec-tively.3.2.1. Selection of extraction and dispersive solventThe selection of an appropriate extraction solvent is of greatimportance to the DLLME process. The extraction solvent shouldmeet the

37、following requirements: it should have a higher densitythan water, a low solubility in water, high extraction capability forthe target analytes, and should form a stable two-phase system inthe presence of a dispersive so

38、lvent when injected to an aqueoussolution. Based on these criteria, CCl4, CHCl3, C2H4Cl2, CH2Cl2, C2Cl4 and C6H5Cl were selected for the study. On the other hand, the selec-tion of a dispersive solvent is limited to solv

39、ents such as acetone,methanol, THF, ethanol and acetonitrile, which are miscible withboth water and the extraction solvents, and could form a cloudystate when injected with the organic extractant into water. Due toa limi

40、ted number of organic extractants, all combinations of usingCCl4, CHCl3, C2H4Cl2, CH2Cl2, C2Cl4 or C6H5Cl (50 ?L) as extrac-tant with acetone, acetonitrile, methanol, THF or ethanol (1.0 mL)as dispersive solvent were inv