Rapid and sensitive detection of the phenoxy acid herbicides in environmental water samples by magnetic solid-phase extraction combined with liquid chromatography-tandem mass spectrometry.

Phenoxy acid herbicides are widely used herbicides that play an important role in improving the yield and quality of crops. However, some research has shown that this kind of herbicide is poisonous to human and animals. In this study, a rapid and sensitive method was developed for the detection of seven phenoxy acid herbicides in water samples based on magnetic solid-phase extraction followed by liquid chromatography and tandem mass spectrometry. Magnetic amino-functionalized multiwalled carbon nanotubes were prepared by mixing bare magnetic Fe3 O4 nanoparticles with commercial amino-functionalized multiwalled carbon nanotubes in water. Then the amino-functionalized multiwalled carbon nanotubes were used to enrich phenoxy acid herbicides from water samples based on hydrophobic and ionic interactions. The effects of experimental variables on the extraction efficiency have been studied in detail. Under the optimized conditions, the method validation was performed. Good linearities for seven phenoxy acid herbicides were obtained with squared regression coefficients ranging from 0.9971 to 0.9989. The limits of detection ranged from 0.01 to 0.02 µg/L. The method recoveries of seven phenoxy acid herbicides spiked at three concentration levels in a blank sample were from 92.3 to 103.2%, with inter- and intraday relative standard deviations less than 12.6%.

Preparation of mesoporous ZrO2-coated magnetic microsphere and its application in the multi-residue analysis of pesticides and PCBs in fish by GC-MS/MS.

A novel mesoporous ZrO2 immobilized magnetic Fe3O4 microsphere (m-ZrO2@Fe3O4) was successfully synthesized and characterized by transmission electron microscope (TEM), X-ray diffractometer (XRD), nitrogen adsorption measurement (NAM), energy-dispersive X-ray analysis (EDX), vibrating sample magnetometer (VSM). Then the resultant m-ZrO2@Fe3O4 and an n-octadecylphosphonic acid modified magnetic microsphere (Fe3O4-OPA) were employed as clean-up co-adsorbents of QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) method for the analysis of 42 pesticides and 7 polychlorinated biphenyls (PCBs) in fish samples. Lipid co-extractives such as fatty acids in QuEChERS extracts could be efficiently removed through the Lewis acid-Lewis base interaction between m-ZrO2@Fe3O4 and carboxylic groups, while some other apolar interferents could be adsorbed through hydrophobic interaction by Fe3O4-OPA. Meanwhile, the magnetic property of adsorbents endows the clean-up procedure with manipulative convenience. Several parameters affecting the clean-up performance were investigated. Under the optimal conditions, the modified QuEChERS method combined with gas chromatography-tandem mass spectrometry (GC-MS/MS) for the multi-class, multi-residue analysis of pesticides and PCBs in fish samples was validated according to linearility, recovery and precision. Good linearities were obtained for all analytes with R(2) larger than 0.9903. Limits of detection (LODs) were found to be in the range of 0.02-4.40 ng/g. The method recoveries of all analytes spiked at three concentration levels in blank fish samples were from 69.8% to 117.1%, with the intra-day and inter-day relative standard deviations (RSDs) less than 13.4% and 16.5%, respectively.

Determination of benzimidazole residues in animal tissue samples by combination of magnetic solid-phase extraction with capillary zone electrophoresis.

Benzimidazole drugs (BZDs) comprise a large number of synthetic anthelmintics, which are widely used in food-producing animals for prophylactic and therapeutic purposes. To protect consumers from the risks related to BZDs residues, a simple, rapid, and efficient method for simultaneous determination of ten BZDs in animal tissues samples was developed. This analytical procedure involved extracting samples with magnetic solid-phase extraction (MSPE) using magnetite/silica/poly (methacrylic acid-co-ethylene glycol dimethacrylate) (Fe(3)O(4)/SiO(2)/poly (MAA-co-EGDMA)) magnetic microspheres, and determination by capillary zone electrophoresis (CZE). To improve the sensitivity of the method, we employed the electrokinetic injection with field-amplified sample stacking technique (FASS). Berbine solution was used as internal standard to minimize the fluctuation of analytical results. Under the optimized extraction conditions, good linearities were obtained for the ten BZDs with the correlation coefficients (R(2)) above 0.9920. The limits of detections (LODs) for ten BZDs were 1.05-10.42 ng/g in swine muscle and 1.06-12.61 ng/g in swine liver, respectively. The intra- and inter-day relative standard deviations (RSDs) of the developed method were less than 13.6%. The recoveries of the ten BZDs for the spiked samples ranged from 81.1% to 105.4% with RSDs less than 9.3%.

Molecular complex-based dispersive liquid-liquid microextraction: analysis of polar compounds in aqueous solution.

A novel molecular complex-based dispersive liquid-liquid microextraction (DLLME) method was established via hydrogen bond interaction between the extractant and the analytes. In this approach, tri-n-butylphosphate (TBP), a Lewis base, was directly used, instead of the traditional water-immiscible organic solvents, as the extractant for DLLME. The phenols (p-benzenediol, m-benzenediol, o-benzenediol and phenol), which are typical Lewis acids, were successfully extracted from environmental aqueous samples. In addition, phase separation was achieved in a disposable polyethylene pipet with the open and narrow tip upside, for a collection of the above extractant layer, i.e. TBP. To achieve satisfactory extraction performance, several extraction parameters, such as type of extractant solvents, extractant volume, pH of sample solution, ionic strength of sample solution and extraction time, were optimized. Additionally, the proposed method was applied to environmental water samples. Under the optimized conditions, the limits of detection and limits of quantification for the phenols were 7-29 and 25-98 µg/L, respectively. The calibration curves showed good linearity (r(2)≥0.9961) over the investigated concentration range. The repeatability of the method was investigated by evaluating the intra- and inter-day precisions. The relative standard deviations (RSDs) obtained were lower than 11.2% and 13.9% at different concentration levels. The recoveries ranged from 83.2% to 117.8%, with RSDs less than 13.1%. The developed approach provides a new way to facilitate DLLME of organic polar compounds from aqueous solutions. Moreover, it enables a convenient collection of solvent less dense making use of a cheap and disposable polyethylene pipet.

Determination of benzimidazole residues in edible animal food by polymer monolith microextraction combined with liquid chromatography-mass spectrometry.

A sensitive method has been developed for the simultaneous determination of 10 benzimidazole residues and some of their metabolites in egg, milk, chicken, and pork. This method is based on the combination of polymer monolith microextraction (PMME) technique with liquid chromatography and electrospray ionization mass spectrometry (LC-ESI/MS). The extraction was performed with a poly(methacrylic acid-co-ethylene glycol dimethacrylate) (MAA-co-EGDMA) monolithic capillary column. Under the optimized extraction conditions, good extraction efficiencies for the targets were obtained with no matrix interference in the subsequent detection. The LODs (S/N=3) for 10 benzimidazoles were found to be 0.56-2.76 ng g(-1) in egg, 0.50-1.41 ng mL(-1) in milk, 0.09-0.28 ng g(-1) in chicken, and 0.08-0.15 ng g(-1) in pork. The recoveries in egg, milk, chicken, and pork matrices ranged from 75.2 to 116.8% spiked at different levels with analytes, with RSDs of <13.7%. The method was later successfully applied for the determination of primary and metabolite residues in eggs after oral administration of albendazole to hens.