Elucidation of Non-Intentionally Added Substances from Plant Fiber/Plastic Composites by UPLC-QTOF/MS.

Plant fiber/plastic composites (PPCs) have been widely used in food contact materials (FCMs) for many benefits, such as their claimed better environmental footprint compared to conventional plastics. However, their safety is still not fully understood and must be comprehensively evaluated. Non-volatiles extracted from six PPCs with different plant fibers and polymer matrices were characterized by employing ultra-high-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry in combination with various spectral libraries and manual elucidation, taking into account spectral similarity and characteristic product ions. A total of 115 compounds were tentatively identified, 50 of which were oligomers or their derivatives from the sample with polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT) as the polymer matrix, and some of them were Cramer rules class III substances based on the threshold of toxicological concern (TTC). Seven reaction products between PLA and PBAT monomers, as well as four derivatives of melamine, were elucidated and well detailed for the first time. In addition, bisphenol S was detected in all samples even though its origin remains to be further explored. Isoprothiolane, as an insecticide and fungicide used to control a range of rice pests, was identified in the sample with rice husk as fillers, experimentally confirming the presence of agrochemicals in samples containing plant fibers.

A novel Hg2+ selective ratiometric fluorescent chemodosimeter based on an intramolecular FRET mechanism.

A irreversible Hg2+ selective ratiometric fluorescence probe FR, a fluorescein fluorophore linked to a rhodamine B hydrazide by a thiourea spacer, was designed and synthesized. The developed probe FR exhibited great ratiometric fluorescence enhancement and remarkable yellow-magenta color change toward Hg2+ with excellent selectivity in aqueous acetone solution, and the ratiometric fluorescence response to Hg2+ was not interfered by other metal cations including Fe3+, Co2+, Ni2+, Cr3+, Zn2+, Pb2+, Cd2+, Ca2+, Mg2+, Ba2+ and Mn2+. The linear range and the detection limit of this supposed ratiometric fluorescence method for Hg2+ were 0.0-10.0x10(-6) and 5x10(-8) M, respectively.

Fluorogenic and chromogenic rhodamine spirolactam based probe for nitric oxide by spiro ring opening reaction.

A new fluorogenic and chromogenic probe rhodamine B spirolactam (1) was developed that in aqueous solutions exhibited a highly selective and sensitive "turn-on" type spectral response toward NO detection following a NO-induced spiro-ring opening reaction in 1.

Colorimetric detection of fluoride in an aqueous solution using Zr(IV)-EDTA complex and a novel hemicyanine dye.

A new highly sensitive and selective colorimetric method for fluoride determination in water is described. The novel reagent used is a hemicyanine dye (HC), which forms a stable complex with Zr-EDTA, the fluoride-binding site, through the hydroxyl groups. The hemicyanine-chelating Zr-EDTA complex (HC-Zr-EDTA) is ready to react with fluoride ion to release HC. This result in remarkable color change of the sensing solutions from red (lambda(max)=513nm) to yellow (lambda(max)=427nm) at pH 4.40. When applied to the colorimetric determination of fluoride ions, a linear range from 3.0x10(-6) to 5.0x10(-5)mol/L and a detection limit of 2.8x10(-6)mol/L with a correlation coefficient of 0.9993 can be achieved under the optimized conditions. Because of the specific affinity of fluorides for the [Zr-EDTA], there is little interference by other ions. This method has been successfully applied to the determination of fluorides in toothpaste samples.