Ultrasonic-Induced Surface Disordering Promotes Photocatalytic Hydrogen Evolution of TiO2.

Surface disordering has been considered an effective strategy for tailoring the charge separation and surface chemistry of semiconductor photocatalysts. A simple but reliable method to create surface disordering is, therefore, urgently needed for the development of high-performance semiconductor photocatalysts and their practical applications. Herein, we report that the ultrasonic processing, which is commonly employed in the dispersion of photocatalysts, can induce the surface disordering of TiO2 and significantly promote its performance for photocatalytic hydrogen evolution. A 40 min ultrasonic treatment of TiO2 (Degussa P25) enhances the photocatalytic hydrogen production by 42.7 times, achieving a hydrogen evolution rate of 1425.4 µmol g-1 h-1 without any cocatalyst. Comprehensive structural, spectral, and electrochemical analyses reveal that the ultrasonic treatment induces the surface disordering of TiO2, and consequently reduces the density of deep electron traps, extends the separation of photogenerated charges, and facilitates the hydrogen evolution reaction relative to oxygen reduction. The ultrasonic treatment manifests a more pronounced effect on disordering the surface of anatase than rutile, agreeing well with the enhanced photocatalysis of anatase rather than rutile. This study demonstrates that ultrasonic-induced surface disordering could be an effective strategy for the activation of photocatalysts and might hold significant implications for the applications in photocatalytic hydrogen evolution, small molecule activation, and biomass conversion.

Optimization of Three Extraction Methods and Their Effect on the Structure and Antioxidant Activity of Polysaccharides in Dendrobium huoshanense.

Dendrobium huoshanense is a famous edible and medicinal herb, and polysaccharides are the main bioactive component in it. In this study, response surface methodology (RSM) combined with a Box-Behnken design (BBD) was used to optimize the enzyme-assisted extraction (EAE), ultrasound-microwave-assisted extraction (UMAE), and hot water extraction (HWE) conditions and obtain the polysaccharides named DHP-E, DHP-UM, and DHP-H. The effects of different extraction methods on the physicochemical properties, structure characteristics, and bioactivity of polysaccharides were compared. The differential thermogravimetric curves indicated that DHP-E showed a broader temperature range during thermal degradation compared with DHP-UM and DHP-H. The SEM results showed that DHP-E displayed an irregular granular structure, but DHP-UM and DHP-H were sponge-like. The results of absolute molecular weight indicated that polysaccharides with higher molecular weight detected in DHP-H and DHP-UM did not appear in DHP-E due to enzymatic degradation. The monosaccharide composition showed that DHPs were all composed of Man, Glc, and Gal but with different proportions. Finally, the glycosidic bond types, which have a significant effect on bioactivity, were decoded with methylation analysis. The results showed that DHPs contained four glycosidic bond types, including Glcp-(1→, →4)-Manp-(1→, →4)-Glcp-(1→, and →4,6)-Manp-(1→ with different ratios. Furthermore, DHP-E exhibited better DPPH and ABTS radical scavenging activities. These findings could provide scientific foundations for selecting appropriate extraction methods to obtain desired bioactivities for applications in the pharmaceutical and functional food industries.

Contamination and Health Risk Assessment of Multiple Mycotoxins in Edible and Medicinal Plants.

Edible and medicinal plants (EMPs) are widely used but are easily infected by harmful fungi which produce mycotoxins. Herein, 127 samples from 11 provinces were collected to investigate 15 mycotoxins based on geographic, demographic, processing, and risk characteristics. A total of 13 mycotoxins were detected, and aflatoxin B1 (0.56~97.00 µg/kg), deoxynivalenol (9.41~1570.35 µg/kg), fumonisin B1 (8.25~1875.77 µg/kg), fumonisin B2 (2.74~543.01 µg/kg), ochratoxin A (0.62~19.30 µg/kg), and zearalenone (1.64~2376.58 µg/kg) occurred more frequently. Mycotoxin levels and species were significantly different by region, types of EMPs, and method of processing. The margin of exposure (MOE) values was well below the safe MOE (10,000). AFB1 exposure from Coix seed and malt consumption in China was of high health concern. The hazard Index (HI) method showed the range of 113.15~130.73% for malt, indicating a public health concern. In conclusion, EMPs should be concerned because of the cumulative effects of co-occurred mycotoxins, and safety management strategies should be developed in follow-up studies.

Comparison of two commercial methods with a UHPLC-MS/MS method for the determination of multiple mycotoxins in cereals.

Immunoassay-based techniques are important on-site screening tools for the detection of mycotoxins in cereals. This study aims to evaluate the trueness, precision, repeatability and cross-reactivity of commercially available test strips, ELISA kits and UHPLC-MS/MS on analyzing zearalenone, ochratoxin A, deoxynivalenol, T-2 toxin and fumonisin B1. The results showed that false negative rate (25.7 %-37.4 %) of all tested mycotoxins by test strips was higher than the false positive rate (0 %-31.0 %). The repeatability of ELISA kits at the declared LOD dispersed from -85.7 % to +98.4 %. ELISA kits were more accurate at 50 % of the maximum residue limit (MRL) of mycotoxins than 150 % and 200 %. All the tested deoxynivalenol/zearalenone derivatives had cross-reactivity with different level, and sample matrix could reinforce this overestimation of target mycotoxin. This study emphasized that higher-quality antibody screening and more analytical performance investigations are need to address for on-site detection of mycotoxins in the future.

Experimental Investigation of Oxide Leaching Methods for Li Isotopes.

To examine the applicability of different leaching methods used to extract secondary oxides from silicate solids for lithium isotope (δ7Li) measurement, this study has conducted leaching experiments on five different types of silicate solids, including a fresh basalt, two weathered basalts, a Yellow River sediment (loess-dominated) and a shale. Four factors were assessed in the experiments: the concentration of the leaching reagent hydroxylamine hydrochloride (HH), the leaching temperature (20 °C vs 95 °C), the leaching time and the reagent/solid ratio. Based on elemental concentrations and Li isotopes, 0.04 mol l-1 hydroxylamine hydrochloride (HH) in 25% v/v acetic acid at room temperature for 1 h with 40 ml g-1 reagent/solid ratio is recommended. At high temperatures, low δ7Li and high magnesium/iron ratios indicate that minerals other than secondary oxides are dissolved. With increased leaching time, there is no evidence for Li isotopic fractionation at room temperature. However, longer leaching time or increased reagent/solid ratios may increase the risk of leaching from non-oxide phases. Meanwhile, results suggest that low concentrations of HH are not sufficient to target the secondary oxides evenly, while high concentrations of HH can leach out more non-oxides. We also examined the optimal oxide leaching method within a full sequential leaching procedure (i.e., exchangeable, carbonate, oxide, clay and residual phases). Elemental concentrations show that no elements exist exclusively in oxides, so it is essential to analyse multi-elemental concentrations to verify that the leaching has accessed this phase in a given sample. Comparing secondary oxides with their corresponding solutions, we estimate the isotopic fractionation (Δ7Lioxide-solution) is -16.8‰ to -27.7‰.

Preparation, characterization and immunoregulatory activity of derivatives of polysaccharide from Atractylodes lancea (Thunb.) DC.

A polysaccharide (ALP-1) extracted from Atractylodes lancea (Thunb.) DC. was carboxymethylated (C-ALP-1), phosphorylated (P-ALP-1) and acetylated (A-ALP-1) to improve its physicochemical properties and bioactivities. The solubility of all derivatives was increased, and the solubility of A-ALP-1 increased to 137.5 mg/mL, which was much higher than the solubility of ALP-1 (15.0 mg/mL). The results of HPSEC-MALLS-RID showed that the molecular weight of polysaccharides was slightly increased after the modification, and the root mean square radius of rotation (Rz) and morphology of polysaccharides in solution were also changed. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) results confirmed that the surface morphology of ALP-1 changed dramatically and the crystallinity decreased after structural modification. From thermal analysis results, the T50 of ALP-1, C-ALP-1, P-ALP-1 and A-ALP-1 were 281.34, 292.14, 333.75 and 298.70 °C, which showed that derivatives had stronger thermal stability than ALP-1. The immunomodulatory activity studies displayed that P-ALP-1 showed the best ability to stimulate RAW264.7 macrophages to release NO, and A-ALP-1 showed the best capacity to stimulate TNF-α and IL-6 releasing. These results indicated that chemical modification could enhance the solubility, the thermal stability and immunomodulatory activity of polysaccharides, which is beneficial for the development and utilization of natural polysaccharides.

Preparation, characterization, and bioactivity evaluation of oligosaccharides from Atractylodes lancea (Thunb.) DC.

Sixteen oligosaccharide monomers with the degree of polymerization 3 to 18 (DP 3 to DP 18) and three active fractions (DP 3-9, DP 8-11, and DP 11-17) were separated from Atractylodes lancea (Thunb.) DC. by optimized fast protein liquid chromatography coupled with refractive index detector (FPLC-RID) and preparation hydrophilic interaction chromatography (Pre-HILIC). Gas chromatography-mass spectrometer (GC-MS), liquid chromatography tandem mass spectrometry (LC-MS/MS), nuclear magnetic resonance (NMR) spectroscopy, and methylation analysis showed that the oligosaccharide in A. lancea was 1-kestose [ß-D-fructofuranosyl-(2 â†’ 1)-ß-D-fructofuranosyl-(2 â†’ 1)-α-D-glucopyranoside] (inulin-type fructooligosaccharides, FOS). Particularly, DP 3-9 showed the best capacity in stimulating phagocytic, NO, and cytokines production on RAW264.7 cells than any other purified oligosaccharide monomers and active fractions. It could also activate T-cells in Peyer's patch cells and enhance the production of colony stimulation factors. Besides, FPLC-RID showed a good capacity for large-scale preparation of DP 3-9 with the recovery of more than 93%. The bioactivity of sixteen FOS monomers (DP 3 to DP 18) and three FOS fractions (DP 3-9, DP 8-11, and DP 11-17) investigated in this study are beneficial for the utilization of FOS as a functional ingredient in novel product development.

Quantifying the impact of recovery during chromatographic purification on the accuracy of lithium isotopic determination by multi-collector inductively coupled plasma mass spectrometry.

RATIONALE: Lithium (Li) isotopes have increasingly been applied as tracers in Earth and planetary sciences and their effectiveness relies upon accurate and precise Li isotopic data. Nowadays, multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) combined with chromatographic purification is the most common strategy for obtaining Li isotopic ratios in natural samples, with a long-term internal precision better than 0.3‰ in most laboratories. However, there is a large discrepancy in the Li isotopic compositions of the same reference materials determined by MC-ICP-MS among international laboratories (e.g. ca 3.5‰ difference for measurements of homogeneous seawater), which has been attributed to insufficient recovery of Li during chromatographic purification. Despite this recognition, the exact impact of Li recovery during purification on Li isotopic determinations by MC-ICP-MS has never been quantified. METHODS: We employed a normal distribution function to model Li elution curves and quantified the Li isotopic fractionation resulting from Li recovery during chromatographic purification. Furthermore, we compared the calculated and measured relative recovery (R) with the Li isotopic ratios determined by ICP-MS to validate our theoretical calculation. RESULTS: The theoretical calculations showed that R should be higher than 99.8% in order to avoid observable Li isotopic fractionation during chromatographic purification at IEECAS. This idea is further supported by the better long-term external precisions for data with R ≥ 99.8% compared with previous values of 99.5% ≤ R < 99.8%. Our results indicated that the large differences in the reported Li isotopic ratios for homogeneous seawater among international laboratories are probably attributable to Li isotopic fractionation occurring during ion exchange chromatography. CONCLUSIONS: Our theoretical calculation via R is the first quantitative and convenient approach for monitoring Li isotopic fractionation during sample purification, ensuring that R ≥ 99.8% can avoid observable Li isotopic fractionation during purification, which will improve the accuracy of Li isotopic measurements by MC-ICP-MS and the comparability among laboratories.

Oligosaccharide-based quality evaluation of Atractylodis rhizome and a strategy for simplifying its quality control.

BACKGROUND: Atractylodis rhizoma, is the dried rhizomes of Atractylodes lancea (Thunb.) DC. or A. chinensis (DC.) Koidz. Both of two are pharmacologically and economically important, while with differences in efficacy. Therefore, an authentication system is vital for evaluation the quality and discrimination adulteration of Atractylodis rhizoma. Fructooligosaccharides (FOS), which are regarded as functional ingredients in Atractylodis rhizoma, have not been used for quality control of Atractylodis rhizoma for shortage of reference compounds. RESULTS: A HPLC-ELSD method was developed for the quantification of FOS in Atractylodis rhizoma. And chemometrics analysis showed that 2 markers including content of degree of polymerization (DP) 12 and total content of DP 3-15 could be used as the main distinctive elements for quality evaluation of Atractylodis rhizome. Actually, the separation and purification of high DP FOS, such as DP 12, is still a challenge because of high polarity. Then DP 5-based qualification evaluation was investigated for quality control of Atractylodis rhizoma. The results showed that A. lancea and A. chinensis could be clearly separated. CONCLUSIONS: DP 5-based quantification method was credible and effectively adopted for solving the shortage of reference compounds and improving the quality control of Atractylodis rhizoma.