Magnetic matrix solid phase dispersion assisted dispersive liquid liquid microextraction of ultra trace polychlorinated biphenyls in water prior to GC-ECD determination

A microfluidic ratiometric electrochemical aptasensor for highly sensitive and selective detection of 3,3',4,4'-tetrachlorobiphenyl

This study proposes a strategy using a microfluidic ratiometric electrochemical aptasensor to detect PCB77 with excellent sensitivity and specificity. This sensing platform combines a microfluidic chip, a wireless integrated circuit system for aptamer-based electrochemical detection, and a mobile phone control terminal for parameter configuration, identification, observation, and wireless data transfer. The sensing method utilizes a cDNA (MB-COOH-cDNA-SH) that is labelled with the redox probe Methylene Blue (MB) at the 5' end and has a thiol group at the 3' end. Additionally, it utilizes a single strand PCB aptamer that has been modified with ferrocenes at the 3' end (aptamer-Fc). Through gold-thiol binding, the labelled probe of MB-COOH-cDNA-SH was self-assembled onto the surface of an Au/Nb2CTx/GO modified electrode. On exposure to aptamer-Fc, it will hybridize with MB-COOH-cDNA-SH to form a stable double-stranded structure on the electrode surface. When PCB77 is present, aptamer-Fc binds specifically to the target, enabling the double-stranded DNA to unwind. Such variation caused changes in the differential pulse voltammetry (DPV) peak currents of both MB and Fc. A substantial improvement is observed in the ratio between the two DPV peaks. Under the optimum experimental conditions, this assay has a response that covers the 0.0001 to 1000 ng mL-1 PCB77 concentration range, and the detection limit is 1.56 × 10-5 ng mL-1. The integration of a ratiometric electrochemical aptasensor with designed microfluidic and integrated devices in this work is an innovative and promising approach that offers an efficient platform for on-site applications.

Isolation of DNA from plant tissues using a miniaturized matrix solid-phase dispersion approach featuring ionic liquid and magnetic ionic liquid solvents

The isolation of high-quality plant genomic DNA is a major prerequisite in many plant biomolecular analyses involving nucleic acid amplification. Conventional plant cell lysis and DNA extraction methods involve lengthy sample preparation procedures that often require large amounts of sample and chemicals, high temperatures and multiple liquid transfer steps which can introduce challenges for high throughput applications. In this study, a simple, rapid, miniaturized ionic liquid (IL)-based extraction method was developed for the isolation of genomic DNA from milligram fragments of Arabidopsis thaliana plant tissue. This method is based on a modification of vortex-assisted matrix solid-phase dispersion (VA-MSPD) in which the trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)imide ([P_6,6,6,14⁺][NTf₂^-]) IL or trihexyl(tetradecyl)phosphonium tris(hexafluoroacetylaceto)nickelate(II) ([P_6,6,6,14⁺][Ni(hfacac)₃^-]) magnetic IL (MIL) was directly applied to treated plant tissue (∼1.5 mg) and dispersed in an agate mortar to facilitate plant cell lysis and DNA extraction, followed by recovery of the mixture with a qPCR compatible co-solvent. This study represents the first approach to use ILs and MILs in a MSPD procedure to facilitate plant cell lysis and DNA extraction. The DNA-enriched IL- and MIL-cosolvent mixtures were directly integrated into the qPCR buffer without inhibiting the reaction while also circumventing the need for additional purification steps prior to DNA amplification. Under optimum conditions, the IL and MIL yielded 2.87 ± 0.28 and 1.97 ± 0.59 ng of DNA/mg of plant tissue, respectively. Furthermore, the mild extraction conditions used in the method enabled plant DNA in IL- and MIL-cosolvent mixtures to be preserved from degradation at room temperature.

Magnetic solid phase extraction and determination of polychlorinated biphenyls in beverages utilizing C60 modified magnetic polyamido-amine dendrimers in combination with gas chromatography-tandem mass spectrometry

Polychlorinated biphenyls (PCBs) are persistent organic pollutants which are widely present in environment and harmful to human health. In this study, an efficient and convenient magnetic solid phase extraction method with C₆₀ modified magnetic polyamido-amine (PAMAM) dendrimers as sorbents was established for enriching trace amounts of PCBs in beverage samples. Gas chromatography-tandem mass spectrometry (GC-MS/MS) was utilized for analysis of PCBs. Parameters affecting extraction efficiency were optimized. Under optimal parameters, good linearity can be achieved in concentration range of 0.001-20 μg L^-1 and 0.002-20 μg L^-1 for nine selected PCBs. The limits of detection for PCBs were in the range of 0.1-0.2 ng L^-1. The spiked recoveries were in the range of 87.0 %-115.1 % (n = 3). The results proved that this established method was reliable for monitoring trace PCBs in beverage samples.

Separation and Enrichment of Sudan III Using Surface Modified Hollow Glass Microspheres and Colorimetric Detection

BACKGROUND

Sudan III has been shown to be carcinogenic to human beings due to the azo chemical structure. A simple, highly selective, and environmentally friendly pretreatment method is usually required before the analysis of Sudan III in complex practical samples due to low concentration and matrix interference.

OBJECTIVE

The aim of this research was to prepare buoyant adsorbents, octyl trimethoxysilane caped hollow glass microspheres (HGMs), and establish a new pretreatment method for the detection of Sudan III in real samples.

METHOD

HGMs were activated and transferred to a flask containing 80 mL ethanol solution (9:1, v/v) and 0.9 mL ammonia. The octyl trimethoxysilane was added to the slurry and covalently coupled on the surface of the HGMs. The modified HGMs were used as adsorbents for the enrichment of Sudan III. After adsorption and desorption, the UV-Vis absorption spectrum was recorded under excitation at 506 nm.

RESULTS

Under the optimum conditions, the linear range and detection limit were 0.10-4.0 mg/L and 0.048 mg/L, respectively. The proposed method was successfully employed to detect Sudan III in chili products with acceptable recoveries of spikes (90.7-102%).

CONCLUSIONS

The adsorbent, which could be separated by flotation, provided a new solid phase extraction method for the pretreatment of complex samples.

HIGHLIGHTS

A new solid phase extraction method was provided for the pretreatment of complex samples. In addition, the adsorbents with high enrichment efficiency can be easily separated by flotation and repeatedly used for separation and enrichment of Sudan III.

Target triggered ultrasensitive electrochemical polychlorinated biphenyl aptasensor based on DNA microcapsules and nonlinear hybridization chain reaction

In this work, we demonstrated an ultrasensitive detection platform for polychlorinated biphenyls (PCBs) based on DNA microcapsules and a nonlinear hybridization chain reaction (NHCR). In the process, first, electrochemical signal molecules (Methylene Blue, MB) were sealed in the prepared DNA microcapsules. In the presence of PCB-72, DNA microcapsules could be dissociated with the conjugation of the aptamer and target, and meanwhile, the released DNA strand could initiate the NHCR and trigger the chain branching growth of DNA dendrimers. Because the released MBs were intercalated into the DNA dendrimer, enhanced electrochemical responses could be detected. This method exhibited ultrahigh sensitivity to PCB-72 with a detection limit of 0.001 ng mL-1. Furthermore, the present aptasensor was also capable of discriminating different PCB congeners. Therefore, the devised label-free and enzyme-free amplification electrochemical aptasensor strategy has great potential for the detection of PCB-72 in real samples, and this strategy may also become an attractive alternative for sensitive and selective small molecule, protein, nucleic acid and nuclease activity detection.

Simultaneous extraction of 32 polychlorinated biphenyls by using magnetic carbon nanocomposite based dispersive microextraction, subsequent dispersive liquid-liquid microextraction with two miscible stripping solvents, and quantitation by GC-μECD

A highly sensitive new method is described for performing dispersive microextractions. It is making use of a magnetic carbon nanocomposite and two miscible organic solvents. The method was applied to simultaneous extraction of 32 polychlorinated biphenyls (PCBs) prior to their quantitation by gas chromatography with electron capture detection. The effects of pH value of sample for both micro solid phase extraction and dispersive liquid-liquid microextraction, of the amount of sorbent, extraction time, type and volume of the miscible organic solvents and of salt addition were optimized. Figures of merit obtained under optimized conditions (sample solution: 500 ml, volume of disperser solvent, ACN, 1.5 mL; volume of extraction solvent, TCB, 30 μL; extraction time: 50 min, 20 mg magnetic sorbent, centrifuge, 5 min, 4000 rpm), include (a) preconcentration factors between 10,880 and 34,000; (b) repeatabilities of ≤14.9%, (c) detection limits between 0.01 and 0.2 ng kg-1, and (d) linear dynamic ranges from 0.05 to 100 ng kg - 1. The method was applied to the simultaneous analysis of residues in (spiked) real samples of fish, milk, packing sheet, and tap waters. Some of the analytes were found to be present in fish samples. The method is simple, rapid, and more sensitive than any of the previously reported ones. Graphical abstract Schematic presentation of simultaneous extraction of 32 polychlorinated biphenyls (PCBs) by using magnetic carbon nanocomposites (MCNs) based dispersive microextraction (M-SPE), subsequent dispersive liquid-liquid microextraction (DLLME) with two miscible stripping solvents, and quantitation by GC-μECD.

Simultaneous enantiomeric analysis of eight pesticides in soils and river sediments by chiral liquid chromatography-tandem mass spectrometry

A rapid and sensitive multi-residue method was developed for the simultaneous quantification of eight chiral pesticides (including diniconazole, metalaxyl, paclobutrazol, epoxiconazole, myclobutanil, hexaconazole, napropamide and isocarbophos) at enantiomeric levels in environmental soils and sediments using chiral liquid chromatography-tandem mass spectrometry based on a combined pretreatment of matrix solid-phase dispersion and dispersive liquid-liquid microextraction (MSPD-DLLME). Under optimized conditions, 0.1 g of solid sample was dispersed with 0.4 g of C18-bonded silica sorbent, and 3 mL of methanol was used for eluting the analytes. The collected eluant was dried and then further purified by DLLME with 550 μL of dichloromethane and 960 μL of acetonitrile as extraction and disperser solvent, respectively. The established method was validated and found to be linear, precise, and accurate over the concentration range of 2-500 ng g^-1 for epoxiconazole, paclobutrazol and metalaxyl and 4-500 ng g^-1 for isocarbophos, hexaconazole, myclobutanil, diniconazole and napropamide. Recoveries of sixteen enantiomers varied from 87.0 to 104.1% and the relative standard deviations (RSD) were less than 10.1%. Method detection and quantification limits (MDLs and MQLs) varied from 0.22 to 1.54 ng g^-1 and from 0.91 to 4.00 ng g^-1, respectively. Finally, the method was successfully applied to analyze the enantiomeric composition of the eight chiral pesticides in environmental solid matrices, which will help better understand the behavior of individual enantiomer and make accurate risk assessment on the ecosystem.