Development of a new microextraction method based on a dynamic single drop in a narrow-bore tube: Application in extraction and preconcentration of some organic pollutants in well water and grape juice samples

Application of an agitation-assisted dispersed solvent microextraction for analysis of naphthalene and its derivatives from aqueous matrices

Agitation-assisted dispersive liquid-liquid extraction without a dispersing solvent is lately receiving considerable attention owing to the low to no solvent loss relative to its predecessor, which suffers severe extracting solvent loss. Herein, we report the application of a simple agitation-assisted dispersive liquid-liquid microextraction method, without a disperser solvent, for the extraction of naphthalene and its derivatives from aqueous solutions. Under the optimised conditions, namely, 25 μL 3:1 mixture of dichloroethane and ethylacetate with 20 s agitation, in 2-mL aqueous solutions containing 10% NaCl, the method demonstrated acceptable figures of merit: linearity-R² ≥ 0.9914 in the concentration range 0.5-50 ng/mL, repeatability (%RSD ≤ 12.9 for n = 15) and limits of detection (0.034-0.081 ng/mL). The recoveries obtained from the spiked dam water sample were also satisfactory (94-103%). These parameters are comparable with those reported in literature, especially for dispersive liquid-liquid microextraction techniques albeit for different analytes. Despite only naphthol being detected in one of the three sampled sites, the method shows considerable promise for routine monitoring of river and dam water quality subject to accuracy validation using certified reference materials.

A review of sample preparation methods for the pesticide residue analysis in foods

The pesticide residues in foods have received increasing attention as one of the most important food safety issues. Therefore, more strict regulations on the maximum residue limits (MRLs) for pesticides in foods have been established in many countries and health organizations, based on the sensitive and reliable analysis methods of pesticide residues. However, the analysis of pesticide residues is a continuing challenge mainly because of the small quantities of analytes as well as the large amounts of interfering substances which can be co-extracted with them, often leading to experimental errors and damage to the analytical instruments. Thus, extensive sample preparation is often required for the pesticide residue analysis for the effective extraction of the analytes and removal of the interferences. This paper focuses on reviewing the recent development in the sample preparation methods for the pesticide residue analysis in foods since 2006. The methods include: liquid-liquid extraction (LLE), supercritical-fluid extraction (SFE), pressurized-liquid extraction (PLE), microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), gel permeation chromatography (GPC), solid-phase extraction (SPE), molecularly imprinted polymers (MIPs), matrix solid-phase dispersion (MSPD), solid-phase micro-extraction (SPME), QuEChERS, cloud point extraction (CPE) and liquid phase micro-extraction (LPME), etc. Particularly their advantages, disadvantages and future perspectives will be discussed.