Combination of dispersive liquid-liquid microextraction and solid-phase microextraction: An efficient hyphenated sample preparation method

Two well-known microextraction methods, dispersive liquid-liquid microextraction (DLLME) and solid-phase microextraction (SPME), were combined, resulting in as an encouraging method. The method, named DLLME-SPME, was performed based on total vaporization technique. For the DLLME step, 1,1,2,2-tetrachloroethane and acetonitrile were used as extraction and disperser solvents, respectively. Halloysite nanotubes-titanium dioxide was used as the fiber coating in the SPME step. The method was applied for the extraction of diazinon and parathion (as the test compounds) in environmental water samples and fruit juices, and gas chromatography-corona discharge ion mobility spectrometry was used as the determination apparatus. Desorption temperature and time, extraction temperature and time, and the volume of the extracting solvent in the DLLME step were optimized as the effective parameters on the extraction efficiency. The relative standard deviations (RSDs) of intra-day were found to be 4-7% and 6-8% for diazinon and parathion, respectively. Also, the RSDs of inter-day were 7-9% and 8-10% for diazinon and parathion, respectively. The limits of quantification and detection were obtained to be 0.015 and 0.005 mu g L-1 for diazinon, and 0.020 and 0.007 mu g L-1 for parathion. A good linearity range (r(2) square 0.993) was obtained in the range of 0.015-3.000 and 0.020-3.000 mu g L-1 for diazinon and parathion, respectively. The high enrichment factors were obtained as 3150 and 2965 for diazinon and parathion, respectively. This method showed high sensitivity with good recovery values (between 87 and 99%) for the extraction of target analytes in the real samples. Overall, the results revealed that the developed DLLME-SPME method had better extraction efficiency than DLLME and SPME alone. (C) 2016 Elsevier B.V. All rights reserved.