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Microstructure of starch plays a vital role in the physicochemical properties. In this study, the microstructure, gelatinization and pasting properties of rice starches after acid, heat and acid-heat treatments were investigated. In our findings, molecular weight and size, amylopectin chain length distribution, degree of branching, amylose content, relative crystallinity, and hot water-solubility of rice starch were varied significantly after acid-heat treatment, showing a synergy between acid and heat. Correspondingly, acid-heat treatment markedly changed gelatinization and pasting properties of rice starch by sharply decreasing gelatinization and pasting temperatures as well as pasting viscosities. Pearson correlation analysis was performed, showing that molecular weight, size, amylopectin chain length distribution, and amylose content were significantly correlated to gelatinization temperatures, and crystallinity was remarkably correlated to gelatinization enthalpy. As for pasting properties, molecular weight and size as the major factors were substantially correlated to pasting viscosities and pasting temperature. This study provides a structure-property correlation for acid-heat treated rice starch, giving scientific basis for the application of starch in food industry.

This presented study describes a method based on high performance liquid chromatography combined with fluorescence detection (HPLC-FLD) using N-(2-iodoacetyl)-1-pyrenemethylamine (NIPA) as a novel fluorescence labeling reagent for the determination of thyreostats in bovine milk. Five thyreostats, belonging to the group of imidazole and thiouracil, were investigated in this work: tapazole (TAP), thiouracil (TU), methylthiouracil (MTU), propylthiouracil (PTU) and phenylthiouracial (PhTU). Thyreostats were specifically purified by a silver ion solid phase extraction (Ag-SPE) cartridge and then labeled using NIPA. The labeled derivatives showed excellent fluorescence property with maximum excitation and emission wavelengths of 330 nm and 375 nm, respectively. The labeled derivatives were separated on a reversed-phase Eclipse SB-C18 column within 12 min. Excellent linearity (R2 > 0.995) of all thyreostats was achieved with the limits of detection (LODs) and the limits of quantitation (LOQs) in the low micrograms per liter range of 0.21–0.30 μg/L and 0.70–1.00 μg/L, respectively. Satisfactory recoveries in the range of 93.5–98.0% were obtained for all thyreostats. The developed method has been successfully applied to analyze thyreostats in bovine milk with good applicability. Thirty bovine milk samples have been investigated, and varying levels of thiouracil were detected in thirteen of these samples. The highest level in the raw milk reached a value of 4.5 μg/L. To our best knowledge, this study is the first to report the presence of naturally occurring thiouracil in milk by HPLC-FLD analysis.

The goal of the presented work is to develop a simple and sensitive high-performance liquid chromatography in combination with fluorescence detection (HPLC-FLD) method for the determination of four nitrofurans (NFs) metabolites compounds (semicarbazide (SEM), 1-aminohydantoin (AH), 3-amino-2-oxazolidinone (AOZ) and 3-amino-morpholinomethyl-2-oxazolidinone (AMOZ)) in foodstuffs. For this goal, we synthesized a novel fluorescence labeling reagent, 4-(carbazole-9-yl)-benzyl chloroformate (CBBC) to label NFs metabolites compounds. NFs metabolites compounds can be labeled rapidly only within 5 min at the room temperature (25 °C). The labeled derivatives showed excellent fluorescence property with maximum excitation and emission wavelengths of 375 nm and 410 nm, respectively. The labeled derivatives were analyzed on a reversed-phase Eclipse XDB-C18 column within 10 min. Excellent linearity (R2 > 0.995) of all NFs metabolites compounds was achieved with the limits of detection (LODs) and the limits of quantitations (LOQs) in the low micrograms per kilogram range of 0.20–0.30 μg·kg−1 and 0.70–1.00 μg·kg−1, respectively. Satisfactory recoveries in the range of 92.5–98.0% were obtained for all NFs metabolites compounds. Using the proposed HPLC-FLD method, we successfully determined four NFs metabolites compounds in different foodstuffs. As promising, this highly sensitive and reliable method would also be extended for the quantitation of NFs metabolites compounds in other samples.

The performance of Fe(III)/H2O2 was extremely enhanced by a novel N-doped ligand dipicolinamide (Dpa) for removing various organic pollutants. This dramatic enhancement of contaminants degradation in Fe(III)-Dpa/H2O2 system under pH≥ 7 was ascribed to the coordinating capacity of Dpa to form the dissolved Fe(III)-Dpa/Fe(II)-Dpa, and the reductive capacity of Dpa to maintain the concentration of Fe(II), which made Dpa improve the catalytic performance of Fe(III) nearly twice as much as Fe(II). Dpa has a strong complexing ability than Cit, NTA, and EDTA to maintain the catalytic activity of Fe(III) without light. The single crystal of Fe-Dpa was obtained to reveal its structure activity relationship. Fe-Dpa was composed of four bonds of Fe-N and two bonds of Fe-Cl. The Fe-Cl bonds were labile sites, which was easily experienced ligand exchange with H2O2, resulting Fe-H2O2 bonds to initiate degradation reaction. The remaining Fe-N bonds were effectively planar, which had a large delocalized π electrons flow domain, enhancing the production of multiple reactive species, including iron(IV/V)-oxo species, HO· and O2-·. An empirical kinetic model of Fe(III)-Dpa/H2O2 system was established. In addition, the evaluation results of the toxicity of Fe-Dpa to larval zebrafish and chinese cabbage displayed that Fe-Dpa possesses low toxicity.

Iohexol, a widely used iodinated X-ray contrast media, is difficult to completely degrade with the traditional water treatment process. Catalytic ozonation with synthesized α-Fe0.9Mn0.1OOH as the catalyst can significantly promote the degradation of iohexol relative to that with ozonation alone. Hydroxyl radicals play a predominant role during the degradation of iohexol. The effect of various factors, including catalyst dose, ozone dose, iohexol concentration and water matrix factors, on the catalytic performance were investigated. The presence of α-Fe0.9Mn0.1OOH in the catalytic system can significantly promote the removal of iohexol and mineralization of the dissolved organic carbon in real water samples. The intermediate products were determined by high-resolution liquid chromatography, and the reaction site was predicted by frontier electron density (FED) calculations. The degradation mechanism of iohexol followed the processes of H-abstraction, amide hydrolysis, amide oxidation, and ·OH substitution. Higher exposure concentrations of iohexol had a negative effect on the survival and hatching rates in the development of zebrafish embryos. The autonomic movement process and heartbeat rate of the zebrafish larvae showed significant differences as the exposure concentration of iohexol increased. The catalytic ozonation process with α-Fe0.9Mn0.1OOH can decrease the toxicity of iohexol containing water.

A new heterogeneous catalyst was developed through immobilizing iron-dipicolinamide complex on silica particles (Fedpa@SiO2) for the degradation of organic pollutants in Fenton-like system at the pH range of 6–10. Fedpa@SiO2 exhibited an excellent catalytic performance to degrade 2,4-dichlorophenol by activating H2O2, and the effects of parameters on its performance were discussed. The reusability of Fedpa@SiO2 was achieved with three successive runs. The complexing ability of dpa avoided the precipitation of Fe, reduced its redox potential, and accelerated the electron transfer among H2O2 and iron, where the iron-oxo species (≡dpaFeV=O), as major reactive species, was generated. The carrier SiO2 contributed to both separating the active sites on the surface of Fedpa@SiO2 and avoiding the self-decomposition of Fedpa. GC-QTOF analysis indicated five aromatic products and two aliphatic acids were identified in the bulk solution, while two aromatic products and one aliphatic acid were detected on the surface of the catalyst.

Iron dipicolinamide (Fedpa), as an efficient Fenton-like catalyst, was fabricated to excite hydrogen peroxide (H2O2) for the removal of 2,4-dichlorophenol (2,4-DCP). The unique structures and the electronic properties of Fedpa were contributed to its excellent catalytic performance in alkaline Fenton process. Fe was chelated with dpa by four Fe–N bonds leaved two labile sites, which reduced the oxidation potential of dpa[FeIII/FeII], dpa[FeV/FeIII] or dpa[FeIV/FeII] to 0.316 V and 1.189 V respectively, and made it easily be bound with H2O2 to initiate the reaction. The results showed that 99.5% removal rate of 2,4-DCP (0.58 mM) was achieved by using 0.027 g/L Fedpa and 5.8 mM H2O2 in 60 min at pH 9.9. The coordination between Fe and dpa enhanced the catalytic efficiency of FeII. The active species generated in Fedpa/H2O2 system contained the iron-oxo species (dpaFeV = O or dpaIV = O), O2− and HO . The iron-oxo species was the main non-radical reactive species for the degradation of 2,4-DCP and some degradation intermediates were detected by GC-QTOF. Furthermore, the influence of factors, such as Fedpa loading, solution pH, temperature and anions (F−, Cl−, SO42−, NO3− and PO43−) on the catalytic performance of Fedpa were also discussed. This process of complexation between Fe and dpa combined with a green oxidant H2O2 presents a new insight for the use of Fenton-like system in the degradation of refractory organics.

The crystal structure of the newly synthesized quaternary MAX phase (Cr2/3Ti1/3)3AlC2 was systematically characterized by various techniques. The space group of (Cr2/3Ti1/3)3AlC2 is determined to be P63/mmc by a combination of selected-area and convergent-beam electron diffraction techniques. Rietveld refinements of the neutron diffraction and X-ray diffraction data show that in (Cr2/3Ti1/3)3AlC2, Ti and Cr are ordered with Ti in the 2a and Cr in the 4f Wyckoff sites of a M3AX2 lattice. It is interesting to find that when the order of the magnetic moment of Cr atoms is considered, the ferromagnetic configuration of (Cr2/3Ti1/3)3AlC2 becomes the ground state. Meanwhile, the Raman-active mode wavenumbers of (Cr2/3Ti1/3)3AlC2 were calculated, and the theoretical data are quite consistent with the experimental data, further proving the ordered crystal structure of this phase. The formation of (Cr2/3Ti1/3)3AlC2 with a unique crystal structure may be related to the distinctly different electronegativities and covalent radii of Cr and Ti atoms.