Dispersive liquid–liquid microextraction coupled with gas chromatography for determination of ethyl tertiary butyl ether and n-butyl ethyl ether in water samples: optimization by factorial design

A dispersive liquid–liquid microextraction (DLLME) technique coupled with gas chromatography-flame ionization detector (GCFID) was developed for preconcentration and determination of ethyl tertiary-butyl ether (ETBE) and n-butyl ethyl ether (n-BEE) in water samples. The variables affecting the extraction efficiency were screened and optimized using experimental design method. A Fractional Factorial Design was applied for screening of variables in order to determine the significant variables affecting the extraction efficiency or peak areas. Then, the significant factors were optimized by using a central composite design (CCD) and the response surface equation was derived. The optimum experimental conditions found included: sample volume, 11.7 mL; extraction solvent (CS2) volume, 46 μL; disperser solvent (acetone) volume, 1 mL; sodium chloride concentration, 3% (w/v); and extraction time selected as 0.5 min. Under the optimum conditions, the enrichment factors were obtained as 146 and 354 for ETBE and n-BEE, respectively. The limits of detections (LODs) were found to be 0.90 μgL−1 (for ETBE) and 0.40 μgL−1 (for n-EBE). Linear dynamic ranges (LDRs) of 10–200 and 5–200 μgL−1 were obtained for ETBE and n-BEE, respectively. The relative tandard deviations (RSD %) for 15, 50 and 200 μg L−1 of each of ETBE and n-BEE (n=7 for each analyte) were obtained as 5.8, 4.0 and 2.3 for ETBE and as 6.2, 4.2 and 2.7 for n- BEE, respectively.

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Keywords: Dispersive liquid–liquid microextraction ، Preconcentration ، Gas chromatography ، Dialkyl ethers