Magnetic solid-phase extraction based on sulfur-functionalized magnetic metal-organic frameworks for the determination of methylmercury and inorganic mercury in water and fish samples.

A novel magnetic metal-organic frameworks (Fe3O4@UiO-66-SH) was successfully prepared by coating Fe3O4 nanospheres with sulfur-functionalized UiO-66. The Fe3O4@UiO-66-SH possesses both the magnetic properties of Fe3O4 and the diverse properties of metal-organic framework (MOF) in one material, which has the superiority of high surface area, easy-operation and strong adsorb ability with mercury, is used for the magnetic solid-phase extraction of methylmercury (MeHg+) and inorganic mercury (Hg2+) in water and fish samples. The analyzes were conducted by high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS). The different pretreatment conditions influencing the extraction recoveries of Hg2+ and MeHg+, including adsorbent amount, pH, extraction time, elution solvent, elution volume, desorption time, co-existing ions and dissolved organic materials were investigated. Under the optimized conditions, the limits of detection (LODs) of Hg2+ and MeHg+ for water samples were 1.4 and 2.6 ng L-1, and the limits of quantification (LOQs) of Hg2+ and MeHg+ for water samples were 4.7 and 8.7 ng L-1. The enrichment factors (EFs) were 45.7 and 47.6 fold for Hg2+ and MeHg+, respectively. The accuracy of the proposed method was demonstrated by analyzing the certified reference material of fish tissue (GBW10029) and by determining the analyte content in spiked water and fish samples. The determined values were in good agreement with the certified values and the recoveries for the spiked samples were in the range of 84.5-96.8%.

Computational design and synthesis of molecular imprinted polymers for selective solid phase extraction of sulfonylurea herbicides.

A high-efficiency approach for the synthesis of molecularly imprinted polymers has been developed and further for the solid-phase extraction of sulfonylurea herbicides in food samples. Molecular simulation approach combined chemometric selected metsulfuron-methyl (MSM) and 2-trifluoromethyl acrylic acid (TFMAA) as the template and the monomer to synthesize the molecularly imprinted polymers (MIPs). Experimental validation confirmed that the MSM-imprinted polymers showed a higher selectivity and affinity to sulfonylurea herbicides. The optimized molecularly imprinted solid-phase extraction (MISPE) conditions, including loading, washing, and eluting conditions, were established. The developed MISPE technology combined HPLC-MSMS was successfully used for the determination of sulfonylurea herbicides in foods. Compared with commercial SPE columns, MISPE showed high affinity, excellent selectivity and low matrix effect. The recoveries of sulfonylurea herbicides spiked in four matrices were between 86.4% and 100.2%, with the relative standard deviations (RSD) in the range of 0.9%-10.5%.

Magnetic C60 nanospheres based solid-phase extraction coupled with isotope dilution gas chromatography-mass spectrometry method for the determination of sixteen polycyclic aromatic hydrocarbons in Chinese herbal medicines.

C60-based magnetic nanospheres were synthesized by coating Fe3O4 nanospheres with silica, then modifying with 3-aminopropyltriethoxysilane as a linker and a C60 fullerene stationary phase. The morphologies, magnetic properties, infrared absorption and carbon content of magnetic nanospheres were studied by TEM, VSM, FTIR and carbon and sulfur analyzer. The magnetic nanospheres were employed for the magnetic solid-phase extraction (MSPE) of 16 polycyclic aromatic hydrocarbons (PAHs) in nine Chinese herbal medicines. The analyses were conducted by isotope dilution gas chromatography-mass spectrometry. The main parameters influencing the extraction, including extraction solvent, adsorbent amount, and extraction time were optimized. Method validation showed that the limit of detection (LOD) was 0.02-0.11 µg/kg, and the limit of quantification (LOQ) was 0.07-0.36 µg/kg. The spiked recoveries rates for 16 PAHs in white peony root were 84.7-107.2%. The relative standard deviation (RSD) was 1.7-8.4%. The established method was further used for the determination 16 PAHs in nine Chinese herbal medicines. Total content of 16 PAHs varied from 73.6 µg/kg (fructus lycii) to 2172.6 µg/kg (astragalus root). The results indicate that the pollution of PAHs in Chinese herbal medicines is serious. The established method can effective detect PAHs contamination in Chinese herbal medicines.

Using stable isotope signatures to delineate the geographic point-of-origin of Keemun black tea.

BACKGROUND: Confirmation of food labeling that claims production in a small geographic region is critical to traceability, quality control and brand protection. In the current study, isotope ratio mass spectrometry (IRMS) was used to generate profiles of δ13 C and δ15 N to determine if the stable isotope signatures of Keemun black tea differ within the three counties that claim production. Other factors (cultivar type, leaf maturity and manufacturing process) were considered for their potential effects. RESULTS: Both cultivar type and leaf maturity have remarkable impact on the δ15 N values of tea leaves, and that the cultivar influenced the δ13 C values. Keemun black tea from Qimen county could be easily discriminated from samples from Dongzhi and Guichi counties based on δ15 N signatures. The k-NN model was cross-validated with an accuracy of 91.6%. Environmental factors and/or genotype seem to be the major reasons for δ15 N differences in Keemun black tea from the selected regions. CONCLUSION: This article provides a potential effective method to delineate the geographic point-of-origin of Keemun black tea based on δ15 N signatures. © 2018 Society of Chemical Industry.