Improved solvent collection system for a dispersive liquid-liquid microextraction of organochlorine pesticides from water using low-density organic solvent

High Density Supercritical Carbon Dioxide for the Extraction of Pesticide Residues in Onion with Multivariate Response Surface Methodology

The excessive use of pesticides is a serious health problem due to their toxicity and bioaccumulation through the food chain. Due to the complexity of foods, the analysis of pesticides is challenging often giving large matrix effects and co-extracted compounds. To overcome this problem, a selective and “green” supercritical fluid extraction method was developed, using neat carbon dioxide as a solvent at pressures of up to 800 bars. A Box–Behnken response surface experimental design was used, with the independent variables of density (0.70−1.0 g mL⁻¹), temperature (40−70 °C), and volume (10−40 mL) of solvent, and the dependent variable of extracted amount of pesticides. The optimum extraction condition was found at the use of 29 mL of supercritical CO₂ at 0.90 g mL⁻¹ and 53 °C (corresponding to 372 bars of pressure). It was observed that increasing the density of CO₂ significantly increased the extraction recovery of endrin and 2,4′-dichlorodiphenyldichloroethane. Matrix-matched calibration curves showed satisfactory linearity (R² ≥ 0.994), and LODs ranged from 0.2 to 2.0 ng g⁻¹. Precision was lower than 11% and recoveries between 80%–103%. Thus, the developed method could efficiently be used for trace analysis of pesticides in complex food matrices without the use of organic solvents.

A novel procedure for phase separation in dispersive liquid-liquid microextraction based on solidification of the aqueous phase

In this paper, an alternative for handling the organic phase after a dispersive liquid-liquid microextraction using organic solvents lighter than water is presented. It is based on solidification (at -18°C) of the aqueous phase obtained after centrifugation, and the decantation, collection and analysis of the liquid organic layer. The extraction of nicotine in toluene, and its determination in eggplant samples was conducted as a proof of concept. The study has been carried out using standards prepared in water and the formation of the dispersion was assisted by sonication. The organic extract was analysed using gas chromatography coupled to mass spectrometry. Satisfactory analytical figures of merit as: limit of detection (0.4µgL(-1), 2ngg(-1) wet sample), limit of quantification (1.2µgL(-1), 6.5ngg(-1) wet sample), within-day precision (RSD=7%), and linearity interval (up to 384µgL(-1) nicotine) were achieved. It constituted a contribution to the handling of organic extracts after microextraction processes.

Up-and-down-shaker-assisted dispersive liquid-liquid microextraction coupled with gas chromatography-mass spectrometry for the determination of fungicides in wine

An up-and-down-shaker-assisted dispersive liquid-liquid microextraction (UDSA-DLLME) method coupled with gas chromatography-mass spectrometry was developed for the determination of fungicides (cyprodinil, procymidone, fludioxonil, flusilazole, benalaxyl, and tebuconazole) in wine. The developed method requires 11 μL of 1-octanol without the need for dispersive solvents. The total extraction time was approximately 3 min. Under optimum conditions, the linear range of the method was 0.05-100 μg L(-1) for all fungicides and the limit of detection was 0.007-0.025 μg L(-1). The absolute and relative recoveries were 31-83% and 83-107% for white wine, respectively, and 32-85% and 83-108% for red wine, respectively. The intra-day and inter-day precision were 0.5-7.5% and 0.7-6.1%, respectively. Our developed method had good sensitivity and high extraction efficiency. UDSA-DLLME is a desirable method in terms of performance and speed.

Water with low concentration of surfactant in dispersed solvent-assisted emulsion dispersive liquid-liquid microextraction for the determination of fungicides in wine

A sample preparation method, dispersive liquid-liquid microextraction assisted by an emulsion with low concentration of a surfactant in water and dispersed solvent coupled with gas chromatography-mass spectrometry, was developed for the analysis of the fungicides cyprodinil, procymidone, fludioxonil, flusilazole, benalaxyl, and tebuconazole in wine. A microsyringe was used to withdraw and discharge a mixture of extraction solvent and 240 μL of an aqueous solution of Triton X-100 (the dispersed agent) four times within 10 s to form a cloudy emulsion in the syringe. This emulsion was then injected into a 5 mL wine sample spiked with all of the above fungicides. The total extraction time was approximately 0.5 min. Under optimum conditions using 1-octanol (12 μL) as extraction solvent, the linear range of the method in analysis of all six fungicides was 0.05-100 μg L(-1), and the limit of detection ranged from 0.013 to 0.155 μg L(-1). The absolute recoveries (n = 3) and relative recoveries (n = 3) were 30-83 and 81-108% for white wine at 0.5, 5, and 5 μg L(-1), and 30-92 and 81-110% for red wine, respectively. The intraday (n = 7) and interday (n = 6) relative standard deviations ranged from 4.4 to 8.8% and from 4.3 to 11.2% at 0.5 μg L(-1), respectively. The method achieved high enrichment factors. It is an alternative sample preparation technique with good performance.

Analysis of triazine herbicides using an up-and-down-shaker-assisted dispersive liquid-liquid microextraction coupled with gas chromatography-mass spectrometry

In dispersive liquid-liquid microextraction, a few hundred microliters to a few milliliters of water-miscible dispersive solvent are commonly used to assist emulsification in aqueous samples. In the present study, a consistent and automatic up-and-down-shaker-assisted dispersive liquid-liquid microextraction (UDSA-DLLME) that does not require a dispersive solvent was developed. The enrichment factors (EFs) of the targets obtained using the automatic shaker were 361-1391 for UDSA-DLLME, 51-77 for ultrasonication, and 298-922 for vortexing. The linearity of the method was in the range 0.2-200μgL(-1), and its limit of detections was within 0.02-0.04μgL(-1). The intraday and interday relative standard deviations ranged from 5.7 to 10.0% and 5.5 to 10.3%, respectively. The relative recoveries of river and lake samples spiked with 2.0μgL(-1) of triazines were 94.2-102.2% and 98.5-104.1%, respectively. The technique provided high repeatability and recovery. No matrix interference from river and lake water was observed. The method also achieved high EFs compared with those obtained through other emulsification methods such as vortexing and ultrasonication. UDSA-DLLME is an alternative sample preparation technique with good performance.