Antioxidant activity of yeast mannans and their growth-promoting effect on Lactobacillus strains.

Yeast mannans from Saccharomyces cerevisiae (123.2 kDa, 40.5 kDa and 21.3 kDa) were prepared. The scavenging abilities of Fe2+, OH˙, and O2˙- and protective capacities against lipid peroxidation and oxidative DNA damage increased with the reduction of the molecular weights of yeast mannans. The highest scavenging abilities of Fe2+, OH˙ and O2˙- (25.32%, 70.8%, and 61.5%) were observed with YM-90, and it showed an anti-lipid peroxidation capacity of 65.82%, which was much stronger than that of vitamin C (VC), with a thiobarbituric acid-reactive substance (TBARS) inhibition rate of 80.41%. However, the highest DPPH scavenging rate (88.7%) was exhibited by YM-30. In addition, the growth-promoting effect of yeast mannans on Lactobacillus strains was further confirmed, and a 54.2% increment of Lactobacillus plantarum ZWR5 cell viability was achieved by YM-90. The results indicated the potential industrial applications of this yeast mannan technology in therapeutic and nutraceutical production.

Performance improvements in all-solution processed inverted QLEDs realized by inserting an electron blocking layer.

Highly efficient, all-solution processed inverted quantum dot light-emitting diodes (QLEDs) are demonstrated by employing 1,3,5-tri(m-pyrid-3-yl-phenyl)benzene (TmPyPB) layer as electron blocking layer. Electron injection from ZnO electron transport layer to quantum dots (QDs) emission layer (EML) can be adjusted by thickness of TmPyPB layer, enabling the balanced charge carriers in QDs EML. With optimal thickness of this TmPyPB adjuster, 59.7% increment in the device current efficiency (from 8.2 to 13.1 cd A-1) and 46.2% improvement in the maximum luminance (from 31916 to 46674 cd m-2) are achieved, compared with those of the control QLED which has double hole transport layer structure. On the other hand, we find luminescence quenching process, which often happens at the interface of ZnO nanoparticles and QDs, is not obvious in our QLEDs, in which the ZnO layer is fabricated in precursor method, and this conclusion is verified through Time Resolution Photoluminescence test. In a word, this strategy provides a direction for optimizing charge carrier balance in all-solution processed inverted QLED.

Synergistic function of doping and ligand engineering to enhance the photostability and electroluminescence performance of CsPbBr3quantum dots.

The photostability issue of CsPbX3(X = Cl, Br, I) quantum dots (QDs) is one of the key origins for the degradation of their luminescence performance, which hinders their application in lighting and displays. Herein, we report a new method combining doping and ligand engineering, which effectively improves the photostability of CsPbBr3QDs and the performance of QD light-emitting diodes (QLEDs). In this method, ZnBr2is doped into CsPbBr3QDs to reduce surface anion defects; didodecyldimethyl ammonium bromide (DDAB) and tetraoctylammonium bromide (TOAB) hybrid ligands, which have strong adsorption with QDs, are employed to protect the surface and enhance the conductivity of QD layer in QLEDs. The photoluminescence (PL) and transmission electron microscopy measurements prove the effectively improved photostability of CsPbX3QDs. Moreover, reduced defects and improved conductivity by doping and hybrid ligands treatment also enable the improved electroluminescence performance of CsPbX3QDs. The maximum luminance and external quantum efficiency of the QLED with optimized CsPbX3QDs are 3518.9 cd m-2and 5.07%, which are 3.6 and 2.1 times than that of the control device, respectively. Combining doping and hybrid ligands makes perovskite QDs have an extremely promising prospect in future applications of high-definition displays, high-quality lighting, as well as solar cells.

Efficient and Stable CdSe/CdS/ZnS Quantum Rods-in-Matrix Assembly for White LED Application.

CdSe/CdS core-shell quantum rods (QRs) are a promising prospect in optoelectronic applications but usually have a relatively low quantum efficiency and stability. Here, we report on an efficient and stable CdSe/CdS/ZnS QRs-in-matrix assembly (QRAs) by growing and embedding CdSe/CdS QRs in ZnS matrices. Structural characterizations show that the CdSe/CdS QRs are encapsulated and interconnected by ZnS in the QRAs structure. The stable ZnS encapsulation renders the CdSe/CdS QRs high quantum efficiency (QE) up to 85%. The QRAs also present high photo- and thermal-stability and can preserve 93% of the initial QE at 100 °C. The QRAs powder presents a light degradation of only 2% under continuous excitation for 100 h, displaying profound potential in optoelectronic applications. White light-emitting diodes (WLEDs) are fabricated by packaging the QRAs powder as phosphor on top of blue GaN chip. The WLED shows high optical performance and light quality.

Highly Efficient and Thermally Stable QD-LEDs Based on Quantum Dots-SiO2-BN Nanoplate Assemblies.

Silica encapsulation effectively elevates the resistance of quantum dots (QDs) against water and oxygen. However, QDs-SiO2 composites present low thermal conductivity and strong thermal accumulation, leading to considerable fluorescence quenching of QDs in optoelectronic devices at high power. Here, a sandwich structural QDs-SiO2-BN nanoplate assembly material (QDs-SiO2-BNAs) is developed to reduce the thermal quenching and enhance the stability of QDs in LEDs. The QDs-SiO2-BNAs is fabricated by embedding QDs-SiO2 into the interlayer of layer-by-layer assembled BN nanoplates, and the BN nanoplates are pretreated by SiO2 encapsulation to strengthen the interaction with QDs-SiO2. This assembly structure endows the QDs with fast heat dissipation and double surface protection against air. The medium power QDs-converted LEDs (QD-LEDs) fabricated by direct on-chip packaging of the QDs-SiO2-BNAs gain 44.2 °C temperature reduction at 0.5 W in comparison with conventional QD-LEDs. After aging, the resulting QD-LEDs present degradation of only 1.2% under sustained driving for 250 h. The QD-LEDs also pass the 1 week reliability test at 85 °C/85% RH with <±0.01 shift of the color coordinates, demonstrating the profound potential of the QDs-SiO2-BNAs in LED lighting and display applications.

[Determination of nine pesticide residues in honey using high performance liquid chromatography-tandem mass spectrometry].

A method is proposed for the simultaneous determination of nine benzimidazole and neonicotinoid pesticides present in honey by employing automatic solid-phase extraction with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). A honey sample was dissolved in a phosphate buffer (pH=7.8) followed by ultrasonic extraction. The extracts were then purified through solid-phase extraction (SPE) with hydrophilic-lipophilic balance (HLB) cartridges. Finally, nitrogen was blown on the obtained mixture, and the mixture was subsequently filtered for conducting HPLC-MS/MS analysis. Nine compounds were detected under the multiple reaction monitoring (MRM) mode, and the corresponding quantification was performed by employing the method of internal standards. The nine detected pesticides demonstrated good linearity in the range of 0.002-0.05 mg/L, with the correlation coefficient values (r2) being higher than 0.99. The limits of detection (LODs) (S/N=3) and limits of quantification (LOQs) (S/N=10) were found to be in the ranges of 0.1-1.0 µg/kg and 0.3-2.0 µg/kg, respectively. Furthermore, the results indicated that the recoveries of the nine detected pesticides range from 78.2%-101.2% at three spiked levels of 5.0, 10.0, and 20.0 µg/kg with a relative standard deviation (RSD) range of 1.3%-14.3% (n=6). Hence, the proposed method is rapid and can be employed for accurate determination of pesticide residues in large quantities of honey samples.

[Determination of characteristic compound in manuka honey by automatic on-line solid phase extraction-liquid chromatography-high resolution mass spectrometry].

A method for the determination of characteristic compound 3,5-dimethoxybenzoate-4-diglucoside (leptosperin) in manuka honey was developed by automatic on-line solid phase extraction-liquid chromatography-high resolution mass spectrometry (SPE-LC-HRMS). The samples were separated on a Dikma Diamonsil Plus C18 column (150 mm×4.6 mm, 5 µm) using the mobile phases of 0.1% (v/v) formic acid aqueous solution and acetonitrile with gradient elution. The compound was detected with negative electrospray ionization (ESI-) in Target-MS2 mode. The results showed that the linear range was 0.5-100.0 mg/L, the correlation coefficient was 0.9993. The limit of detection (LOD, S/N ≥ 3) and limit of quantification (LOQ, S/N ≥ 10) of the method was 3 mg/kg and 10 mg/kg, respectively. The recoveries at the spiked levels of 50.0, 100.0, 200.0 mg/kg (10.0, 20.0, 50.0 mg/kg in black locust samples) were in the range of 82.0%-95.2% with the relative standard deviations ranging from 2.7% to 9.7% (n=6). The proposed method was applied to 95 mature honey samples from hives in New Zealand including 12 different kinds and 50 commercial honey samples from four different countries. The method is fast, sensitive and accurate to provide technical support to solve the judgment of the manuka honey imported from New Zealand.

[Determination of three coriaria lactones in honey by ultra high performance liquid chromatography-high resolution mass spectrometry].

A method for the determination of three coriaria lactone residues in honey was developed using ultra high performance liquid chromatography-high resolution mass spectrometry. The honey samples were extracted with 0.2 mol/L phosphate buffer solution (pH = 7.5), and the extracts were cleaned up with Waters HLB solid phase extraction cartridges. The extracted components were separated on a Phenomenex C18 column by gradient elution. The qualitative and quantitative analyses were operated under t-MS2 by high resolution mass spectrometry. The results showed that the limits of detection and quantification for the three coriaria lactones in a spiked blank honey were 0.05 mg/kg and 0.1 mg/kg, respectively. The recoveries of the three coriaria lactones spiked in blank honey samples at the levels of 0.1 to 0.5 mg/kg were 86.3%-95.6% with the RSDs of 3.0%-8.4%. The method was applied for the determination of the manuka honey from New Zealand, and tutin was detected in one of the samples. The results showed that the method is suitable for the determination of the three coriaria lactone residues in honey.

[Determination of fructo-oligosaccharides in milk powder by high performance liquid chromatography-quadrupole/electrostatic field orbitrap high resolution mass spectrometry].

A method of high performance liquid chromatography-quadrupole/electrostatic field Orbitrap high resolution mass spectrometry (HPLC-Q/Orbitrap MS) was developed to determine fructo-oligosaccharides in milk powder. The milk powder samples were dissolved in deionized water. Subsequently, an aqueous solution of zinc acetate was used to precipitate protein. After centrifugation, the final aqueous solution was filtered by a polytetrafluoroethylene (PTFE) membrane with pore size of 0.22 µm. The analytes were separated on a Carbohydrate column (100 mm x 2.1 mm, 2.6 µm) through gradient elution with the combination of acetonitrile and 0.1% formic acid aqueous solution. The target-MS/MS templates were performed at isolation window of m/z 4.0 and collision energy of 30 eV in positive mode to extract the accurate product ion mass of analytes. Under the optimal condition, 1-kestose (GF2), nystose (GF3) and 1-F-ß-fructofuranosyl nystose (GF4) were well separated and the accuracy of extracted mass routinely detected was below 5 x 10(-6) (5 ppm). The whole analysis time is only ten minutes. The detection limits for GF2 and GF3 were 100 µg/kg, and the detection limit for GF4 was 55 µg/kg. Good linearities were obtained in their respective linear ranges with correlation coefficients higher than 0.998. The average recoveries at three spiked levels (5, 10 and 20 mg/kg) were in the range of 75.8%-107.3% and the relative standard deviations (RSDs) were in the range of 1.6% - 8.3%. The proposed method is simple, sensitive, fast and only in need of precipitation of proteins. The interference of matrix can be eliminated through the selection of product ion. The results were convenient and reliable and thus can be used in the large batch determination of any milk powder.

[Determination of four insecticide residues in honey and royal jelly by gas chromatography-negative chemical ionization mass spectrometry].

A method was developed for the determination of four insecticide residues in honey and royal jelly by gas chromatography-negative chemical ionization mass spectrometry (GC-NCI/MS). The honey and royal jelly samples were treated with different preparation methods as the result of the different components. The honey sample was extracted with ethyl acetate and cleaned up with primary second amine, and the royal jelly sample was extracted with acetonitrile-water (1:1, v/v), and cleaned up with a C18 solid-phase extraction column. Finally, the extracts of the honey and royal jelly were analyzed by GC-NCI/MS in selected ion monitoring (SIM) mode separately. External standard calibration method was used for quantification. The linearities of calibration curves of the four insecticides were good with the correlation coefficients greater than 0.99 in the range of 50-500 microg/L. The limits of the detection (LODs) of the four insecticides were in the range of 0.12- 5.0 microg/kg, and the limits of the quantification (LOQs) were in the range of 0.40-16.5 microg/kg. The recoveries of the four insecticides spiked in honey and royal jelly at three spiked levels (10, 15 and 20 microg/kg) were in the range of 78.2 -110.0%, and the relative standard deviations (RSDs) were all below 14%. The sensitivity and selectivity of this method were good with no interfering peaks. The proposed method is simple quick and effective to analyze the four insecticide residues in honey and royal jelly.

[Determination of trifluralin residue in aquatic products and edible oils by gas chromatography-negative chemical ionization mass spectrometry].

A confirmatory method was established for the determination of trifluralin residue in aquatic products and edible oils with the technique of offline disperse solid phase extraction and gas chromatography-negative chemical ionization mass spectrometry (DSPE-GC-MS/NCI). Trifluralin was extracted from aquatic products and edible oils with acetonitrile, and liquid-liquid partitioning formed by adding anhydrous magnesium sulfate followed by a simple cleanup step known as dispersive solid-phase extraction. The aliquot was analyzed by GC-MS/NCI using isotope internal standard method. The method was reliable and stable. The recoveries of trifluralin were in the range from 80% to 100% at three spiked levels of 1.0, 2.0, and 3.0 microg/kg, and the RSDs were not more than 10.3%. The linearity of method was good from 1 to 40 microg/L, and the LOD was 0.02 microg/kg. This method can be used as a conclusive evidence method for the determination of trifluralin residue in aquatic products and edible oils.

[Study on the safety of blue light leak of LED].

In this paper, the blue light properties of LED illumination devices have been investigated. Against the status quo of China's LED lighting, we measured the spectrum component of LED lamps and analyzed the photobiological safety under the current domestic and international standards GB/T 20145-2006/CIE S009/E: 2002 and IEC62471: 2006 standards as well as CTL-0744_2009-laser resolution, which provides the reference to the manufacture of LED lighting lamps as well as related safety standards and laws. If the radiance intensity of blue light in LED is lower than 100 W x m(-2) x Sr(-1), there is no harm to human eyes. LEDs will not cause harm to human eyes under normal use, but we should pay attention to the protection of special populations (children), and make sure that they avoid looking at a light source for a long time. The research has found that the blue-rich lamps can affect the human rule of work and rest, and therefore, the LED lamps with color temperature below 4 000 K and color rendering index of 80 are suitable for indoor use. At the same time, the lamps with different parameters should be selected according to the different distances.

[Determination of methylglyoxal in Manuka honey of New Zealand by high performance liquid chromatography].

An HPLC method was developed for the determination of methylglyoxal in Manuka honey of New Zealand. The honey sample was dissolved in water and mixed with o-phenylenediamine solution for derivatization. After the reaction for at least 8 h in the dark at room temperature, the solution was filtered with 0.22 microm membrane and injected into an HPLC system for analysis. The separation was carried out on a Kromasil reversed phase column with gradient elution. The mobile phases were methanol and 0. 1% (v/v) acetic acid aqueous solution. The detection wavelength was 318 nm. The external standard method was used for quantitation. The linear range of methylglyoxal was 1-50 mg/L with a correlation coefficient of 0. 999 9. The LOD (S/N = 3) and LOQ (S/N = 10) were 0.02 mg/L and 0.06 mg/L, respectively. The recoveries at the spiked levels of 50, 100, 200 mg/kg were 98.3%-101.5% and the RSDs (n = 5) were less than 5%. The derivative of methylglyoxal was stable within 24 h. The results showed that the pretreatment of this method is simple and the sensitivity, the recovery and repeatability are good. This method can be used for the quality control of Manuka honey of New Zealand, and also for the detection of methylglyoxal in Chinese honey.

[Determination of four kinds of illegal additive residues in sprouts and source beans by high performance liquid chromatography-tandem mass spectrometry].

A reversed-phase high performance liquid chromatography coupled with tandem mass spectrometric (LC-MS/MS) method was developed for the determination of 4-chlorophenoxyacetic acid, 6-benzylaminopurine, enrofloxacin and norfloxacin residues in sprouts and source beans. The sample was extracted by acetonitrile containing 0.1% acetic acid and concentrated. The chromatographic analysis was carried out on a C18 column with methanol and 0.1% formic acid solution as the mobile phases in gradient elution program. The MS analysis was set in electrospray ionization mode and separated to two segments of positive and negative modes. The precursor ions were m/z 189.9, 226.1, 359.9 and 320.1, while the product ions for quantification were m/z 127.0, 91.2, 315.9 and 276.2 for 4-chlorophenoxyacetic acid, 6-benzylaminopurine, enrofloxacin and norfloxacin, respectively. The calibration curves showed good linearity in the range of 5 - 200 microg/L with correlation coefficients more than 0.995. The limits of detection (LODs) were 1 microg/kg and the limits of quantification (LOQs) were 5 microg/kg for the four compounds spiked in mung bean sprouts and mung beans. The recoveries of the four compounds spiked at three levels of 5.0, 10.0 and 20.0 microg/kg ranged from 70% to 91%, with the relative standard deviations (RSDs) less than 14%. The method established is accurate, sensitive, simple, and has considerable advantages in the analysis of the four kinds of illegal additive residues in sprouts and beans simultaneously.

[Determination of five pyrrolizidine alkaloids in honey by liquid chromatography-tandem mass spectrometry].

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the determination of five pyrrolizidine alkaloids (PAs) (monocrotaline, senkirkine, retrorsine, seneciphylline and senecionine) in honey. The honey samples were dissolved in 0.1 mol/L hydrochloric acid solution and a strong-cation exchange column was used to purify and concentrate the target analytes. The separation of the analytes was carried out on a Phenomenex C18 column (100 mm x 4.6 mm, 2.6 microm) using the mobile phases of acetonitrile and 5 mmol/L ammonium acetate-0.1% (volume percentage) formic acid aqueous solution with gradient elution. The separated compounds were detected in multiple reaction monitoring (MRM) mode via positive electrospray ionization (ESI+). The calibration curves were of good linearity in the range of 1-100 microg/L (r > 0.99). The limit of quantification of the method was 1.0 microg/kg. The average recoveries were between 73.1% to 107.1% at three spiked levels (1, 20 and 50 microg/kg) with the relative standard deviations (RSDs) in the range of 4.1% to 17.0%. The proposed method was applied to different kinds of honey from China, New Zealand, Spain and Australia. The samples included rape, vitex, sunflower, cotton, tilia tree, date, acacia, buckwheat, manuka and eucalyptus honey. Monocrotaline, senkirkine and retrorsine were not detected in the collected honey samples. However, seneciphylline and senecionine were found in most of the honey samples. The concentrations of seneciphylline and senecionine were 11.0 -31.1 microg/kg and 8.3-29.1 microg/kg, respectively.

[Determination of exogenous gamma-amylase residue in honey].

A novel method for the determination of exogenous gamma-amylase residue in honey using liquid chromatography-isotope ratio mass spectrometry (LC-IRMS) was established. After pre-separation by gel column chromatography, the gamma-amylase in honey samples was separated from the sugars. The gamma-amylase was then used to catalyze maltose into glucose. This enzymatic reaction was under the conditions of 55 degrees C and 0.03 mol/L phosphate buffer solution (pH 4.5) for 48 h. The maltose and glucose in the above enzymatic reaction solution were separated using liquid chromatography. By measuring the content of glucose with isotope ratio mass spectrometry, the gamma-amylase in honey can be determined. The linear range of gamma-amylase was 5 - 200 U/kg with the quantification limit of 5 U/kg. The recoveries were between 89.6% and 108.2% with the relative standard deviations from 3.3% to 4.9%. This method was used to analyze 38 honey and rice syrup samples, and the detection rate of gamma-amylase was 76.3%. To further verify the detection capability of this method, an authentic honey was adulterated with 15% (mass fraction) rice syrup. The gamma-amylase content in this sample was 10.2 U/kg. This method can effectively identify honey adulteration with rice syrups from the perspective of enzymology.

[Determination of kojic acid in foods using high performance liquid chromatography-tandem mass spectrometry].

The quantification method for the determination of kojic acid in foods using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was developed. For solid samples, the kojic acid was extracted with acetonitrile; for liquid samples, they were diluted with water, then deproteinized by the deposition with zinc acetate and potassium ferrocyanide. The analytes were determined by HPLC-MS/MS on a C18 column with 5 mmol/L ammonium acetate/formic acid solution as mobile phases. The analysis of kojic acid was performed under selected reaction monitoring (SRM) mode by selecting one parent ion and two daughter ions as qualitative ions with [13C6]-kojic acid as the internal standard, and the most abundant daughter ion as quantitative ion. The limits of quantification (S/N > 10) were 0.1 mg/kg for the solid samples, and 2.5 mg/kg for the liquid samples. The good linearity (r > 0.99) was achieved for the target compound over the range of 0.1 - 2.0 mg/L. The recoveries at three levels for kojic acid were from 72.6% to 114% with the relative standard deviations no more than 11.4%. The method is simple and practical, and can be applied to most of matrices which may contain kojic acid as food additives. It can meet the qualitative and quantitative requirements for import and export foods.

[A novel solid phase extraction column combined with ultra performance liquid chromatography/tandem mass spectrometry for selective enrichment and determination of clenbuterol in pork].

A simple and efficient method based on a novel solid phase extraction (SPE) cartridge and ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/ MS) was developed for the determination of clenbuterol residue in pork. The minced pork sample was ultrasonically extracted by 5% (v/v) perchloric acid and centrifuged at 10 000 r/min for 15 min, then the supernatant was purified by an SMCX cartridge, which is a novel SPE column based on homemade silica matrix with two mixed modes of reversed-phase and strong cation exchange, for the selective enrichment and purification of the analyte. The linear range of the method was 0.25 - 50 microg/kg with a correlation coefficient of 0.998 2. The average recoveries ranged from 62.2% to 72.0% at the three spiked levels of 1.25, 12.5 and 50 microg/kg with the relative standard deviations (RSDs) between 4.2% and 6.1%. The limit of detection (S/N = 3) was 0.05 microg/kg. The method is simple, fast and can be extended to enrich and determine beta-agonist drugs.

[Determination of chloramphenicol in propolis by high performance liquid chromatography-tandem mass spectrometry].

A method for the determination of chloramphenicol in propolis was developed by high performance liquid chromatography-tandem mass spectrometry. The flavones were removed with lead acetate solution after the extraction of the sample with water. The extract was cleaned up by liquid-liquid extraction. Internal standard method was used for quantitative analysis. The linear range was 0.05 - 2.0 microg/L and the correlation coefficient (r2) was 0.9996. The limit of detection (LOD, S/N = 3) and limit of quantitation (LOQ, S/N = 10) were 0.1 microg/kg and 0.3 microg/kg, respectively. The recoveries ranged from 70.1% to 94.0% while the intra-day precision lower than 10% and inter-day precision lower than 15%. The method reduced the interference by removing most of the flavones and was suitable for the determination of chloramphenicol in propolis.

[Determination of amoxicillin in honey by high performance liquid chromatography-tandem mass spectrometry].

A method for the determination of amoxicillin in honey by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was established. The samples were dissolved by phosphate buffer and cleaned-up by solid phase extraction (SPE) cartridge. The analytes were determined by HPLC-MS/MS on a C18 column with methanol and 0.1% (v/v) formic acid solution as mobile phases with gradient elution. The analysis of amoxicillin was performed under selected reaction monitoring mode by selecting one parent ion and two daughter ions as qualitative ions and the most abundant daughter ion as quantitative ion. The external standard was used for quantitative analysis in this method. The calibration curve showed good linearity in the range of 2.0-100.0 microg/L with good precision and accuracy (r2 > 0.99). The limit of detection (LOD) and limit of quantitation (LOQ) were 2.0 microg/kg and 5.0 microg/kg, respectively. The average recoveries of amoxicillin in spiked honey ranged from 74.2% to 81.7% with the intra-day precisions (relative standard deviations, RSDs) from 2.8% to 7.8% and the inter-day precisions (RSDs) from 9.1% to 11.3%. This method is convenient and suitable for the determination of amoxicillin in honey.