Review: Microextraction Technique Based New Trends in Food Analysis

Food chemistry is the study and classification of the quality and origin of foods. The identification of definite biomarkers and the determination of residue contaminants such as toxins, pesticides, metals, human and veterinary drugs, which are a very common source of food-borne diseases. The food analysis is continuously demanding the improvement of more robust, sensitive, highly efficient, and economically beneficial analytical approaches to promise the traceability, safety, and quality of foods in the acquiescence with the consumers and legislation demands. The traditional methods have been used at the starting of the 20th century based on wet chemical methods. Now it existing the powerful analytical techniques used in food analysis and safety. This development has led to substantial enhancements in the analytical accuracy, precision, sensitivity, selectivity, thereby mounting the applied range of food applications. In the present decade, microextraction (micro-scale extraction) pays more attention due to its futures such as low consumption of solvent and sample, throughput analysis easy to operate, greener, robotics, and miniaturization, different adsorbents have been used in the microextraction process with unique nature recognized with wide range applications.

Development of a screening analytical method for the determination of non-dioxin-like polychlorinated biphenyls in chicken eggs by gaschromatography and electron capture detection

A sensitive and reproducible screening analytical method is here proposed for the determination of six non dioxin-like polychlorinated biphenyls (NDL-PCBs, congener 28, 52, 101, 138, 153, 180) in chicken eggs based on accelerated solvent extraction (ASE) procedure for the fat extraction and determination, a solid phase extraction (SPE) sample clean-up process, and a gas chromatography - electron capture detection (GC-ECD) analysis. The optimized chromatographic separation, in less than 25 min, returned good responses for the six NDL-PCBs in the range of 2.5-60.0 µg L^-1, with correlation coefficients always higher than 0.9995. Instrumental limits of detection were between 0.08-0.35 µg L^-1, corresponding to 0.05 and 0.23 ng g^-1 fat in the matrix, while method detection limits, calculated on spiked egg samples, ranged from 1.6 to 3.5 ng g^-1 fat. The method has been extensively validated in terms of selectivity, sensitivity, recovery, precision, ruggedness and measurement uncertainty, following the European Directives.

Magnetic effervescent tablet-assisted ionic liquid-based dispersive liquid-liquid microextraction of polybrominated diphenyl ethers in liquid matrix samples

Herein, a novel method, magnetic effervescent tablet-assisted ionic liquid-based dispersive liquid-liquid microextraction (META-IL-DLLME), was pioneered for extraction and preconcentration of polybrominated diphenyl ethers (PBDEs) in liquid matrix samples. In this proposed method, a magnetic effervescent tablet, containing CO₂ sources, ionic liquids and Fe₃S₄ magnetic nanoparticles (MNPs), combines extractant dispersion and magnetic recovery into one-step. Fe₃S₄ was synthesized, characterized and applied it for the first time to the newly developed method, and its extraction recoveries (ERs) for PBDEs were 20.8-32.0% higher than those of conventional Fe₃O₄ MNPs. The increased ERs of Fe₃S₄ resulted from its larger specific surface area and pore size. Some important parameters were rigorously optimized, such as kinds of magnetic nanoparticles, effervescent agents, extraction solvents and their volumes, elution solvents, extraction temperature and salt addition. Under the optimized conditions, the META-IL-DLLME method combined with HPLC-DAD analysis gave the linear ranges of 0.1-0.5-100 µg L^-1 with correlation coefficients of > 0.9990. The ERs ranged from 80.7% to 99.3%, and the limits of detection and quantitation were 0.012-0.078 µg L^-1 and 0.04-0.26 µg L^-1, respectively. The intra- and inter-day precisions, expressed as relative standard deviations (RSD, n = 6), were 1.32-4.83% and 1.99-4.25%, respectively. To evaluate its matrix effect, the relative recoveries of PBDEs from tap and river water, skim and whole milk, pregnant women and women serum samples at three fortification levels (2.0, 5.0 and 20.0 µg L^-1) were in the range of 77.3-106.7%. Overall, the commercial Fe₃O₄ MNPs can only be used for magnetic separation in microextraction procedures, while Fe₃S₄ MNPs gave the higher adsorption and extraction efficiency for organic analytes besides the convenient magnetic separation. Therefore, the results obtained in this study provide a superior alternative for the conventional magnetic separation and adsorbent material. Also, this newly developed method has a great potential in routine monitoring of liquid matrix samples.

A simple solvent collection technique for a dispersive liquid-liquid microextraction of parabens from aqueous samples using low-density organic solvent

A simple technique for the collection of an extraction solvent lighter than water after dispersive liquid-liquid microextraction combined with high-performance liquid chromatography with ultraviolet detection was developed for the determination of four paraben preservatives in aqueous samples. After the extraction procedure, low-density organic solvent together with some little aqueous phase was separated by using a disposable glass Pasteur pipette. Next, the flow of the aqueous phase was stopped by successive dipping the capillary tip of the pipette into anhydrous Na(2)SO(4). The upper organic layer was then removed simply with a microsyringe and injected into the high-performance liquid chromatography system. Experimental parameters that affect the extraction efficiency were investigated and optimized. Under optimal extraction conditions, the extraction recoveries ranged from 25 to 86%. Good linearity with coefficients with the square of correlation coefficients ranging from 0.9984 to 0.9998 was observed in the concentration range of 0.001-0.5 μg/mL. The relative standard deviations ranged from 4.1 to 9.3% (n = 5) for all compounds. The limits of detection ranged from 0.021 to 0.046 ng/mL. The method was successfully applied for the determination of parabens in tap water and fruit juice samples and good recoveries (61-108%) were achieved for spiked samples.

Determination of phthalate esters in cow milk samples using dispersive liquid-liquid microextraction coupled with gas chromatography followed by flame ionization and mass spectrometric detection

A simple and economic method for the analysis of phthalate esters, dimethyl phthalate, diethyl phthalate, di-iso-butyl phthalate, di-n-butyl phthalate, and di-2-ethylhexyl phthalate in cow milk samples by means of gas chromatography-flame ionization detection and gas chromatography-mass spectrometry has been developed. In this work, NaCl and ACN were added to 5 mL of the milk sample as the salting out agent and extraction solvent, respectively. After manual shaking, the mixture was centrifuged. In the presence of NaCl, a two-phase system was formed: upper phase - acetonitrile containing phthalate esters -and lower phase - aqueous phase containing soluble compounds and the precipitated proteins. After the extraction of phthalate esters from milk, a portion of supernatant phase (acetonitrile) was removed, mixed with 1,2-dibromoethane at microliter level and injected by syringe into NaCl solution. After the extraction of the selected phthalate esters into 1,2-dibromoethane, phase separation was performed by centrifugation and the enriched analytes in the sedimented phase were determined by gas chromatography-flame ionization detection and gas chromatography-mass spectrometry. Under the optimum extraction conditions, low limits of detection and quantification between 1.5-3 and 2.5-11 ng/mL, respectively was observed. Enrichment factors were in the range of 397-499. The relative standard deviations for the extraction of 100 ng/mL of each phthalate ester were in the range of 3-4% (n = 6). Finally, some milk samples were successfully analyzed using the proposed method and two analytes, di-n-butyl phthalate and di-2-ethylhyxel phthalate, were determined in them in nanogram per milliliter level.