In this work, the defective Cu-BDC with different defect concentration and Cu1+/Cu2+ coordinatively unsaturated sites (CUS) content were designed and synthesized by introducing defective linkers with different pKa values. The...
Nitrofuran
(NF) is a class of broad-spectrum antibiotics that are
used illegally in animal feeding. NF and its metabolites have proven
to pose potential risk to human health. To address the current analytical
needs to quantify low levels of NF metabolites in animal foods, a
sensitive method was developed for simultaneous detection of four
NF metabolites in fish products by an ultraperformance liquid chromatography-diode
array detector (UPLC-DAD). With 2-nitrobenzaldehyde (2-NBA) as the
derivatizing reagent, the metabolites were hydrolyzed and derivatized
under the assistance of thermostatic ultrasound. Compared with the
current detection methods, the time of the derivatization reaction
has been shortened from 16 to 2 h. The relative coefficient of four
NF metabolite derivatives reached more than 0.998, with excellent
linear relationship. The limits of detection (LODs) and limits of
quantification (LOQs) of six repeated determinations reached 0.25–0.33
and 0.80–1.10 μg/kg, respectively. For all four NF metabolites,
the limit of detection of the method was below the minimum required
performance limit (MRPL) of 1.0 μg/kg, which makes it compatible
with the EU requirements. The recoveries ranging from 89.8 to 101.9%
with relative standard deviation below 6.5% were obtained for all
of the NF metabolites. What’s more, this method was successfully
applied for the determination of four NF metabolites in the fish products.
As a promising approach, this method could also be extended for the
quantitation of NF metabolites in aquaculture and poultry products.
Microplastics (MPs) are novel pollutants, which can carry toxic contaminants and are released in biota and accumulate. The adsorption behavior of MPs and aged MPs has attracted extensive attention. In this paper, the aging process of polystyrene (PS) and poly (butyleneadipate-co-terephthalate) (PBAT) plastics under ultraviolet (UV) irradiation at a high temperature and their adsorption properties for the contaminant diclofenac sodium (DCF) before and after aging was investigated. There are many factors affecting the adsorption capacity of MPs. In this experiment, three aspects of MPs, organic pollutants, and environmental factors are explored. The Freundlich model as well as the pseudosecondary kinetic model is more applicable to the process of DCF adsorption by MPs. The main effects of adsorption of organic pollutants by MPs are electrostatic interactions, hydrogen-halogen bonds, and hydrophobic interactions. The adsorption capacity of the UV-aged MPs on DCF is significantly enhanced, and the order of adsorption capacity is Q(A-PBAT) (27.65 mg/g) > Q (A-PS) (23.91 mg/g) > Q (PBAT) (9.30 mg/g) > Q (PS) (9.21 mg/g). The results show that more active sites are generated on the surface of MPs after aging, which can enhance their adsorption capacity for organic pollutants. This adsorption mechanism will increase their role as contaminant carriers in the aquatic food chain.
Microplastics (MPs) will cause compound pollution by combining with organic pollutants in the aqueous environment. It is important for environmental protection to study the adsorption mechanism of different MPs for pollutants. In this study, the adsorption behaviors of malachite green (MG) and rhodamine B (RhB) on polyethylene (PE) and polyvinyl chloride (PVC) were studied in single systems and binary systems, separately. The results show that in single system, the adsorptions of between MPs for pollutants (MG and RhB) are more consistent with the pseudo-second-order kinetics and Freundlich isotherm model, the adsorption capacity of both MPs for MG is greater than that of RhB. The adsorption capacities of MG and RhB were 7.68 mg/g and 2.83 mg/g for PVC, 4.52 mg/g and 1.27 mg/g for PE. In the binary system, there exist competitive adsorption between MG and RhB on MPs. And the adsorption capacities of PVC for the two dyes are stronger than those of PE. This is attributed to the strong halogen-hydrogen bond between the two dyes and PVC, and the larger specific surface area of PVC. This study revealed the interaction and competitive adsorption mechanism between binary dyes and MPs, which is of great significance for understanding the interactions between dyes and MPs in the multi-component systems.
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