Characterization and Application in Natural Rubber of Leucaena Leaf and Its Extracted Products.

Leucaena is a fast-growing tree in the legume family. Its leaf contains a significant amount of protein and is thus widely used as fodder for cattle. To broaden its application in the rubber field, the effects of Leucaena leaf powder and its extracted products on the cure characteristics and mechanical properties of natural rubber were investigated. The extraction of Leucaena leaf was carried out by using a proteolytic enzyme at 60 °C. The digested protein was separated from the residue by centrifugation. Both digested protein and residue were then dried and ground into powder, namely digested protein powder and residual powder, respectively, before being characterized by Fourier transform infrared spectroscopy, scanning electron microscope, thermogravimetric analysis, X-ray diffraction, particle size determination, and protein analysis. After being added to natural rubber at 3 parts per hundred rubber, they significantly reduced both the scorch time and the optimum cure time of the rubber compounds, probably due to the presence of nitrogen-containing substances, without a significant sacrifice of the mechanical properties. For instance, the optimum cure time decreased by approximately 25.5, 35.4, and 54.9% for Leucaena leaf powder, residual powder, and digested protein powder, respectively. Thus, they can be used as green and sustainable fillers with a cure-activation effect in rubber compounding.

Development of doubly porous composite adsorbent for the extraction of fluoroquinolones from food samples.

A doubly porous microcomposite polyaniline/graphene oxide/octadecyl-bonded silica magnetite (PANI/GOx/C18-SiO2-Fe3O4) alginate adsorbent was developed and employed to extract fluoroquinolones. The Fe3O4 facilitated rapid and convenient for the separation of the adsorbent from sample solutions. The double porosity of the alginate hydrogel enhanced the surface area of the polyaniline coating. The developed method exhibited good linearity of 0.0010-50 µg L-1 for danofloxacin; 0.0050-50 µg L-1 for norfloxacin, ciprofloxacin and enrofloxacin; and 0.010-50 µg L-1 for sarafloxacin and difloxacin. The limits of detection were between 0.001 and 0.010 µg L-1 with RSD below 9.0%. The PANI/GOx/C18-SiO2-Fe3O4 adsorbent was utilized to extract fluoroquinolones from honey, milk and egg samples and satisfactory extraction recoveries were achieved ranged from 80 to 98%. The developed adsorbent has good stability which can be reused up to 7 times, is simple to prepare and convenient to use for the extraction fluoroquinolones.

A hierarchically porous composite monolith polypyrrole/octadecyl silica/graphene oxide/chitosan cryogel sorbent for the extraction and pre-concentration of carbamate pesticides in fruit juices.

A hierarchically porous structured composite monolith sorbent of polypyrrole-coated graphene oxide and octadecyl silica incorporated in chitosan cryogel (PPY/GOx/C18/chitosan) was synthesized and used as solid-phase extraction sorbent for the determination of carbamate pesticides. Various factors affecting the characteristics of the adsorbents (chemistry of the sorbent, polymerization time, concentrations of graphene oxide and octadecyl silica) and the extraction efficiency using the prepared sorbents, such as sample loading, desorption conditions, sample volume, sample flow rate, sample pH, and ionic strength, were investigated and optimized. Under the optimal conditions of sorbent preparation and extraction, the developed composite monolith sorbent provided wide linear responses from 1.0 to 500 µg L-1 for carbofuran and diethofencarb, from 0.5 to 500 µg L-1 for carbaryl, and from 2.0 to 500 µg L-1 for isoprocarb. The limits of detection using HPLC-UV at 203, 220, and 208 nm were in the range of 0.5-2.0 µg L-1. When the composite monolith sorbent was applied for the pre-concentration and determination of carbamate in fruit juices, good recoveries (84.1-99.5%) were achieved. The developed sorbents were porous and exhibited low back pressure enabling their use at high flow rates during sample loading. Extraction and clean-up were highly efficient, and the good physical and chemical stability of the sorbent enables reuse up to 13 times. Graphical abstract ᅟ.