Development of Liquid Phase Microextraction Method Based on Solidification of Floated Organic Drop for Extraction and Preconcentration of Organochlorin Pesticides in Water Samples
Department of Chemistry, Faculty of Sciences, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Iran.Analytica chimica acta (Impact Factor: 4.51). 10/2008; 626(2):166-73. DOI: 10.1016/j.aca.2008.08.001
A simple and efficient liquid-phase microextraction (LPME) in conjunction with gas chromatography-electron capture detector (GC-ECD) has been developed for extraction and determination of 11 organochlorine pesticides (OCPs) from water samples. In this technique a microdrop of 1-dodecanol containing pentachloronitrobenzene (internal standard) is delivered to the surface of an aqueous sample while being agitated by a stirring bar in the bulk of solution. Following completion of extraction, the sample vial was cooled by putting it into an ice bath for 5 min. Finally 2 muL of the drop was injected into the GC for analysis. Factors relevant to the extraction efficiency were studied and optimized. Under the optimized extraction conditions (extraction solvent: 1-dodecanol; extraction temperature: 65 degrees C; sodium chloride concentration: 0.25 M; microdrop and sample volumes: 8 muL and 20 mL respectively; the stirring rate: 750 rpm and the extraction time: 30 min), figures of merit of the proposed method were evaluated. The detection limits of the method were in the range of 7-19 ngL(-1) and the RSD% for analysis of 2 mugL(-1) of OCPs was below 7.2% (n=5). A good linearity (r(2)> or =0.993) and a relatively broad dynamic linear range (25-2000 ngL(-1)) were obtained. After 30 min of extraction, preconcentration factors were in the range of 708-1337 for different organochlorine pesticides and the relative errors ranged from -10.1 to 10.9%. Finally the proposed method was successfully utilized for preconcentration and determination of OCPs in different real samples.
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- "The extraction recovery (ER) were 53.58% and 62.89%, and enrichment factor (EF) were 96 and 114, for chlorpyrifos and TCP, respectively. The relatively low extraction efficiencies were in the range of reported extraction efficiencies in previous studies using the DLLME-SFO method.[7,30,31]The EF and ER were calculated for analytes (10 µg L –1 , n = 5) using the following equations: o.f aq.ini o.f o aq.ini aq "
ABSTRACT: This article reports an alternative method for simultaneous extraction and determination of chlorpyrifos and its main degradation product 3,5,6-trichloro-2-pyridinol (TCP) in water samples which involves dispersive liquid–liquid microextraction based on solidification of floating organic droplet followed by high-performance liquid chromatography with ultraviolet detection. Methanol (1.0 mL) and 1-dodecanol (70 µL) were used as the disperser solvent and extraction solvent, respectively. After the floated extraction solvent had solidified in an ice bath, it was dissolved with methanol. Under the optimized conditions, enrichment factors for chlorpyrifos and TCP were 96 and 114, respectively. Linear calibration curves were obtained in the range of 1–50 µ g L −1, with correlation coefficients (R 2) > 0.9955. The limits of detection were 0.12 µ g L −1 for chlorpyrifos and 0.10 µ g L −1 for TCP. The recoveries of spiked real water samples ranged between 84.54% and 102.29%, with the relative standard deviation being 0.80–14.03%.
- "Consequently, residue analyses of OCPs in waters and soils by developing analytical procedure continue to be an active area of research in recent years (Santos & Galceran, 2004). Trace analysis of OCPs in water is usually performed by gas chromatography (GC) combined with a previous an extraction or a pre-concentration step including traditional liquid–liquid extraction (LLE) (Barcelo´, 1993, Fatoki & Awofolu, 2003; Tahboub et al., 2005), solid phase extraction (SPE) (Aguilar et al., 1996; 1997), solid phase microextraction (SPME) (Page & Lacroix, 1997; Aguilar et al., 1999; Tomkins & Barnard, 2002; Li et al., 2003; Dong et al., 2005) and the more recently developed liquid phase microextraction under different names, i.e., dispersive liquid–liquid microextraction (DLLME) (Cortada et al., 2009a; Leong & Huang, 2009; Tsai & Huang, 2009), liquid-phase microextraction (LPME) (Huang & Huang, 2007; Farahani et al., 2008), single-drop microextraction (SDME) (Cortada et al., 2009b), polymer-coated hollow fiber microextraction (PC-HFME) (Basheer et al., 2004), stir bar sorptive extraction (SBSE) (Leo´n et al., 2003; Pe´rez-Carrera et al., 2007), ultrasound 61 recovery of analytes. However, general drawbacks of this method are difficult to automate and it requires using a dispersive solvent which usually decreases the partition coefficient of analytes into the extraction solvent (Rezaee et al., 2006; Pena-Pereira et al., 2009). "
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ABSTRACT: A new and versatile liquid-phase microextraction method combined with gas chromatography (GC) analysis was applied for the extraction and determination of some aliphatic alcohols. Microlitre volumes of 1-undecanol were delivered on to the surface of the aqueous sample and the sample was agitated for a desired time. Then, the sample vial was cooled by inserting it into an ice bath for 5 min. The solidified solvent was transferred into a suitable vial and immediately melted, of which 1.0 µL was injected into GC for analysis. The parameters affecting the microextraction efficiency such as sampling temperature, stirring rate, nature and volume of the extracting solvent, salt addition and extraction time were investigated. The optimal microextraction conditions were established as: sample solution temperature, 60°C; stirring rate, 1250 rpm; volume of the extracting solvent, 8.0 µL (1-undecanol); salt concentration, 4 M NaCl and extraction time of 20 min. Under the optimal conditions, detection limits of the method were in the range of 3–56 µg L−1 and the relative standard deviations for determination of the alcohols were in the range of 2.2–11.9. Dynamic linearity of the alcohols was found to be in the range of 60–800 µg L−1. After 20 min of extraction period, the pre-concentration factors for the alcohols were in the range of 13–358. Finally, the method was applied for determination of trace amounts of the alcohols in several real aqueous samples and satisfactory results were obtained.
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