Dispersive Liquid-liquid Microextraction Extraction Research Articles

Extraction and Analysis of Methadone in Exhaled Breath Condensate Using a Validated LC-UV Method.

A combined microextraction and separation method is presented for the determination of methadone in exhaled breath condensate (EBC) which is a promising non-invasive biological component for monitoring drug concentrations. In this work, dispersive liquid-liquid microextraction (DLLME) and ultrasonic liquid-liquid microextraction (ULLME) procedure coupled with a validated liquid chromatography method were used for analysis of methadone in EBC collected using an in-house cold trap setup. The method has been validated according to the FDA guidelines using EBC-spiked samples and tested on a number of EBC samples collected from patients. The best DLLME conditions involved the use of a disperser solvent of methanol (1 mL), extraction solvent of chloroform (200 mL), EBC sample pH of 10.0 and centrifugation at 6000 rpm for 5 minutes. The conditions for ULLME were 150 mL of chloroform and the samples were sonicated for 4 minutes. The method was validated over the concentration range of 0.5-10 mg/L-1 in EBC. Inter- and intra-day precision and accuracy were less than 5 % where the acceptable levels are less than 20%. Furthermore, the validated method was successfully applied for the determination of methadone in patients' EBC samples. The outcomes indicate that the developed LC-UV combined with DLLME and/or ULLME extraction methods can be employed for the extraction and separation of methadone in EBC samples.

Response surface methodology for optimization of cyanamide analysis by in situ derivatization and dispersive liquid–liquid microextraction

Cyanamide is widely used for agricultural purposes; therefore, its residues can be found in water. A new method was developed for its quantification using in situ derivatization with 2,6‐dimethyl‐4‐quinolinecarboxylic acid N‐hydroxysuccinimide ester followed by dispersive liquid–liquid microextraction (DLLME) and high‐performance liquid chromatography/fluorescence analysis. Multivariate chemometric techniques were successfully used to obtain the optimum conditions for direct derivatization and DLLME extraction. Derivatization parameters and DLLME extraction conditions were optimized by a two‐step design, 2k factorial design for screening, and central composite design for optimization. Best derivatization conditions were addition of 600 μL of derivatizing reagent, a temperature of 4 ºC, and pH 8.5, whereas for optimum extraction 800 μL of solvent, 30% NaCl conc. w/v, and pH 3.8 were chosen.The analytical performance of the method for routine analysis was evaluated. Excellent linearity was achieved from 10 to 200 µg L−1 with a correlation factor of 0.9996. Precision ranged from 3.5% to 5.5% for intraday assays and 8.5% to 8.6% for interday assays. The mean recoveries performed on water from different origins (ground, river, sea, tap, and mineral) at three levels of concentration (20, 75, and 200 µg L−1) ranged from 90.2% to 110.2%. Copyright © 2014 John Wiley & Sons, Ltd.

Determination of Triazine Herbicides in Environmental Samples by Dispersive Liquid-Liquid Microextraction Coupled with High Performance Liquid Chromatography

A simple, rapid, efficient, and environmentally friendly method for the determination of five triazine herbicides in water and soil samples was developed by using dispersive liquid-liquid microextraction (DLLME), coupled with high performance liquid chromatography-diode array detection (HPLC-DAD). The water samples were directly used for DLLME extraction. For soil samples, the target analytes were first extracted by water-methanol (99:1, v/v). In the DLLME extraction method, chloroform was used as an extraction solvent, and acetonitrile as a dispersive solvent. Under the optimum conditions, the enrichment factors of DLLME were in the range between 183-221. The linearity of the method was obtained in the range of 0.5-200 ng/mL for the water sample analysis, and 1-200 ng/g for the soil samples, respectively. The correlation coefficients ranged from 0.9968 to 0.9999. The limits of detection were 0.05-0.1 ng/mL for the water samples, and 0.1-0.2 ng/g for the soil samples. The proposed method has been successfully applied to the analysis of target triazine herbicides (simazin, atrazine, prometon, ametryn, and prometryn) in water and soil samples with satisfactory results.

Evaluation of dispersive liquid–liquid microextraction for the simultaneous determination of chlorophenols and haloanisoles in wines and cork stoppers using gas chromatography–mass spectrometry

Dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography–mass spectrometry (GC–MS) was evaluated for the simultaneous determination of five chlorophenols and seven haloanisoles in wines and cork stoppers. Parameters, such as the nature and volume of the extracting and disperser solvents, extraction time, salt addition, centrifugation time and sample volume or mass, affecting the DLLME were carefully optimized to extract and preconcentrate chlorophenols, in the form of their acetylated derivatives, and haloanisoles. In this extraction method, 1 mL of acetone (disperser solvent) containing 30 μL of carbon tetrachloride (extraction solvent) was rapidly injected by a syringe into 5 mL of sample solution containing 200 μL of acetic anhydride (derivatizing reagent) and 0.5 mL of phosphate buffer solution, thereby forming a cloudy solution. After extraction, phase separation was performed by centrifugation, and a volume of 4 μL of the sedimented phase was analyzed by GC–MS. The wine samples were directly used for the DLLME extraction (red wines required a 1:1 dilution with water). For cork samples, the target analytes were first extracted with pentane, the solvent was evaporated and the residue reconstituted with acetone before DLLME. The use of an internal standard (2,4-dibromoanisole) notably improved the repeatability of the procedure. Under the optimized conditions, detection limits ranged from 0.004 to 0.108 ng mL −1 in wine samples (24–220 pg g −1 in corks), depending on the compound and the sample analyzed. The enrichment factors for haloanisoles were in the 380–700-fold range.

Dispersive liquid–liquid microextraction combined with high performance liquid chromatography–fluorescence detection for the determination of carbendazim and thiabendazole in environmental samples

A rapid and sensitive method for the determination of carbendazim (methyl benzimidazole-2-ylcarbamate, MBC) and thiabendazole (TBZ) in water and soil samples was developed by using dispersive liquid–liquid microextraction (DLLME) coupled with high performance liquid chromatography with fluorescence detection. The water samples were directly used for the DLLME extraction. For soil samples, the target analytes were first extracted by 0.1 mol L −1 HCl. Then, the pH of the extract was adjusted to 7.0 with 2 mol L −1 NaOH before the DLLME extraction. In the DLLME extraction method, chloroform (CHCl 3) was used as extraction solvent and tetrahydrofuran (THF) as dispersive solvent. Under the optimum conditions, the enrichment factors for MBC and TBZ were ranged between 149 and 210, and the extraction recoveries were between 50.8 and 70.9%, respectively. The linearity of the method was obtained in the range of 5–800 ng mL −1 for water sample analysis, and 10–1000 ng g −1 for soil samples, respectively. The correlation coefficients ( r) ranged from 0.9987 to 0.9997. The limits of detection were 0.5–1.0 ng mL −1 for water samples, and 1.0–1.6 ng g −1 for soil samples. The relative standard deviations (RSDs) varied from 3.5 to 6.8% ( n = 5). The recoveries of the method for MBC and TBZ from water samples at spiking levels of 5 and 20 ng mL −1 were 84.0–94.0% and 86.0–92.5%, respectively. The recoveries for soil samples at spiking levels of 10 and 100 ng g −1 varied between 82.0 and 93.4%.