Facile Synthesis of Multi-Emission Nitrogen/Boron Co-Doped Carbon Dots from Lignin for Anti-Counterfeiting Printing.

The transformation of lignin with natural aromatic structure into value-added carbon dots (CDs) achieves a win-win situation for low-cost production of novel nanomaterials and reasonable disposal of biomass waste. However, it remains challenging to produce multi-emission CDs from biomass for advanced applications. Herein, a green and facile approach to preparing multi-emission CDs from alkali lignin via N and B co-doping is developed. The obtained N and B co-doped CDs (NB-CDs) show multi-emission fluorescence centers at 346, 428 and 514 nm under different excitations. As the doping amount of N and B increases, the fluorescence emission band gradually shifts to 428 and 514 nm, while that at 346 nm decreases. The fluorescence mechanism is explored through the research of the structure, composition and optical performance of NB-CDs in combination with density functional theory (DFT) calculations. It demonstrates that the effect of doping with B-containing functional groups on the fluorescence emission behavior is multivariate, which may be the crucial contribution to the unique multi-emission fluorescence of CDs. The multi-emission NB-CDs with prominent stability are applied for multilevel anti-counterfeiting printing. It provides a promising direction for the sustainable and advanced application of biomass-derived CDs, and the theoretical results highlight a new insight into the deep understanding of the multi-emission fluorescence mechanism.

Microwave-assisted catalytic pyrolysis of moso bamboo for high syngas production.

Microwave-assisted pyrolysis of moso bamboo with the activated carbon-supported iron(III) ion catalyst was carried out with the aim of obtaining high quality and quantity syngas(H2 + CO). The effect of the catalyst on moso bomboo pyrolysis involving the temperature-rising characteristics, product distribution, tar conversion and gas compositions were investigated. The results indicated that the catalyst improved the microwave-absorption capability and increased the maximum reaction temperatures. The formation of gases was promoted by the catalyst mainly at the expense of the tar, indicating the catalyst had an excellent activity for the tar conversion .The catalyst had the positive influence on the formation of syngas with the maximum content reaching up to 81.14 vol% with H2/CO being 1.04 and inhibited the production of CH4 and CO2. The loading of iron(III) ion into activated carbon exerted a significant influence on bamboo pyrolysis. The addition of the catalyst increased the thermal efficiency of the reaction system.

[Recent applications of graphene-based materials in capillary electrophoresis].

Graphene and graphene-based materials have been widely applied in biochemical and chemical analysis because of its unique physical and chemical properties. Recent applications of graphene-based materials in capillary electrophoresis (CE) were highlighted, such as modification of amperometric detection electrode, preparation of monolithic column, modification of capillary inner wall and modification of microchip. The potential application of graphene materials in CE is discussed in this review.

Cytokinins can act as suppressors of nitric oxide in Arabidopsis.

Maintaining nitric oxide (NO) homeostasis is essential for normal plant physiological processes. However, very little is known about the mechanisms of NO modulation in plants. Here, we report a unique mechanism for the catabolism of NO based on the reaction with the plant hormone cytokinin. We screened for NO-insensitive mutants in Arabidopsis and isolated two allelic lines, cnu1-1 and 1-2 (continuous NO-unstressed 1), that were identified as the previously reported altered meristem program 1 (amp1) and as having elevated levels of cytokinins. A double mutant of cnu1-2 and nitric oxide overexpression 1 (nox1) reduced the severity of the phenotypes ascribed to excess NO levels as did treating the nox1 line with trans-zeatin, the predominant form of cytokinin in Arabidopsis. We further showed that peroxinitrite, an active NO derivative, can react with zeatin in vitro, which together with the results in vivo suggests that cytokinins suppress the action of NO most likely through direct interaction between them, leading to the reduction of endogenous NO levels. These results provide insights into NO signaling and regulation of its bioactivity in plants.

Classification of Maojian teas from different geographical origins by micellar electrokinetic chromatography and pattern recognition techniques.

A micellar electrokinetic chromatography (MEKC) method was applied for the identification of geographical origins of Chinese green teas. Under the optimized conditions, chromatographic profiling of collected Maojian tea samples was obtained. Based on MEKC-UV profiling, twenty-four tea samples were successfully differentiated according to the relative peak areas of selected peaks in the chromatograms. Tea samples from Hubei and Henan provinces were classified correctly by hierarchical cluster analysis model (HCA) and principal component analysis (PCA). The application of linear discriminant analysis (LDA) gave correct assignation percentages of 100% for the training set and the prediction set. The overall results demonstrated that MEKC with pattern recognition could be successfully applied to discriminate Maojian teas according to their geographical origins.

[Determination of 16 polycyclic aromatic hydrocarbons in airborne particle samples using two-step thermal desorption and gas chromatography-mass spectrometry].

A method for the determination of 16 polycyclic aromatic hydrocarbons (PAHs) in airborne particle samples was developed using two-step thermal desorption and gas chromatography-mass spectrometry (GC-MS). The thermal desorption conditions and GC-MS parameters were optimized. The results showed that the detection limits (LODs) of this method varied from 0.14 to 0.42 ng/m3. The average recoveries were ranged from 52.7% to 97.9%, and the relative standard deviations (RSD) were ranged from 8.0% to 18.4%. The method was applied to analyze 32 collected airborne particle samples. In comparison with the traditional method, this method can avoid the waste of organic solvents and also shorten the analysis time. It is a green method, and beneficial for the environment and the analysts.

[Simultaneous determination of cocaine and its metabolite ecgonine methyl ester in human blood using microwave extraction-gas chromatography].

A method was developed for the simultaneous determination of cocaine (COC) and its metabolite ecgonine methyl ester (EME) in human blood using gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detection (GC-FID). The blood sample was prepared by microwave extraction (MWE). The optimal parameters of MWE were as follows: 6 mL of chloroform-isopropanol (9: 1, v/v) mixture as extraction solvent, the pH value of the sample was adjusted at 10.0 with 0.05 mol/L Na2CO3-NaHCO3 buffer, the extraction was performed at 40 degrees C for 6 min. The COC and EME in the extract were qualified using GC-MS and quantitated using GC-FID. The average recoveries of COC and EME were from 79.91% to 99.85%, the relative standard deviations were less than 3.10%, and the limits of detection (LOD) were 60 and 40 mg/L, respectively. In the method COC and EME were detected without derivatization. The method is rapid, accurate and sensitive, and can be used for the simultaneous determination of COC and EME in blood samples.

[Determination of amphetamines in human urine using microwave extraction-gas chromatography].

A method has been developed for the determination of methamphetamine (MA), 3,4-methylenedioxyamphetamine (MDA) and 3,4-methylenedioxymethamphetamine (MDMA) in human urine using microwave extraction-gas chromatography(GC). To improve the extraction efficiency, experimental parameters of the extraction, including extraction solvent and its amount, pH value of the urine sample, extraction time and temperature were investigated. The optimal conditions were as follows: the pH value of urine sample at pH 12, cyclohexane as extraction solvent, extraction at 40 degrees C for 10 min. The average recoveries of MA, MDA and MDMA with this extraction method were 92.25%, 85.94% and 91.50%, the relative standard deviations were 5.5%, 5.5% and 6.1%(n = 5), and the limits of detection were 10, 20 and 20 ng/mL, respectively. Using this method, MA, MDA and MDMA need not be derivatized and can be separated from the matrix. The results indicate that the developed method is rapid, accurate and sensitive, and can be used for the simultaneous determination of MA, MDA and MDMA in urine samples.

[Simultaneous determination of four beta-lactam antibiotics in milk by solid-phase extraction-micellar electrokinetic chromatography].

A solid-phase extraction (SPE)-micellar electrokinetic chromatography (MEKC) method was developed for the simultaneous determination of four beta-lactam antibiotics (ampicillin, amoxicillin, penicillin V and cephalexin) in spiked milk samples. The milk samples were extracted by SPE after protein precipitation. The analysis was performed by MEKC at 18 kV with phosphate buffer containing sodium dodecyl sulfate (SDS) and the detection was carried out at 210 nm. The four antibiotics could be baseline-separated less than 9 min. The linearities in 0.5 - 20 mg/L could be constructed with the correlation coefficients between 0.994 3 - 0.997 6, and the limits of detection were 0.16 - 0.20 mg/L. The average recoveries of antibiotics from milk were over 70% except amoxicillin. The method is sensitive, specific and easy for the determination of beta-lactam antibiotic residues in milk.

[Determination of methamphetamine in human blood using microwave extraction-gas chromatography].

A method was developed for the determination of methamphetamine (MAM) in human blood using microwave extraction-gas chromatography (GC). To improve the extraction efficiency, experimental parameters on the extraction, including such as extraction solvent and its amount, pH value of blood sample, extraction time and temperature were investigated. Comparing with conventional liquid-liquid extraction method, the microwave extraction showed better efficiency under the optimal conditions. The optimal conditions were as follows: the pH of blood sample at 13, ethyl acetate as extraction solvent, extraction at 30 degrees C for 8 min. The average recovery of MAM with this extraction method was 81.4%, and the relative standard deviation was 6.4%. The limit of detection was 220 microg/L for MAM in the blood. Using this method, MAM need not be derivatized and can be separated from the matrix. The results indicate that the developed method is rapid, accurate and sensitive, and can be used for the determination of MAM in blood samples.

Chiral separation of ephedrine isomers by capillary electrophoresis using bovine serum albumin as a buffer additive.

A method utilizing bovine serum albumin (BSA) as buffer additive for chiral separation by means of capillary electrophoresis is described. Parameters that affect chiral separation, such as buffer pH, buffer concentration, BSA concentration, and organic modifier, are investigated. Baseline resolution of ephedrine-pseudoephedrine and norephedrine-norpseudoephedrine isomers are achieved in an uncoated capillary with a 20 mmol/L phosphate buffer at pH 9.0 in the presence of 10 micromol/L BSA and 15% (v/v) 2-propanol at 25 degrees C. The developed method can be applied for the analysis of ephedra plant extracts that contain the four test drugs.

[Determination of scopolamine and atropine in Flos Daturae by RP-HPLC].

OBJECTIVE: To develop a quantitative analytical procedure of scopolamine and atropine in Flos Daturae using RP-HPLC. METHOD: The two alkaloids were separated on a Hypersil BDS C18 column (4.6 mm x 250 mm, 5 microm) with a mobile phase of 0.02 mol x L(-1) sodium acetate buffer (containing 0.02% triethanolamine and the pH was adjusted to 6.0 with acetic acid)-methanol (60:40) and a detection wavelength of 215 nm. The flow rate was 1.0 mL x min(-1) and the column temperature was maintained at room temperature. RESULT: The mean recovery was (99.6 +/- 1.8)% for scopolamine and (100.4 +/- 1.5)% for atropine. CONCLUSION: This method was simple, accurate and sensitive.

[Solid phase extraction and room temperature phosphorimetry coupling technique and its application].

The principle and application in the environmental analysis of Solid Phase Extraction (SPE) combined with Room Temperature Phosphorescence (RTP) analysis were reviewed. The principle, device, separation modes, operation procedures and application of SPE were commented. The merits and shortages in the operation procedure and quantitative analysis of classic RTP were also summarized. The potential application in the trace sample analysis and the advantage of coupling technique of SPE and RTP were indicated. The sensitivity and selectivity of the coupling technique could be greatly increased because of the strong enrichment ability of the SPE materials and the high selectivity of RTP. So far the technique has been successfully used in the analysis of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzofurans (PClDBFs) in the environmental samples according to their phosphorescence emission after preconcentration on the Whatman 1PS filter paper and C18 or C8 SPE membranes.

A new simple and rapid electrochemical method for the determination of hydroxyl radical generated by Fenton reaction and its application.

A simple and rapid electrochemical method to detect the hydroxyl radical is described. This method employed the reaction between.OH and dimethyl sulfoxide (DMSO) to generate quantitatively formaldehyde, which then reacted with hydrazine hydrochloride at pH 6.2. The product showed a second-order derivative cathodic wave with the peak potential of -1.08 V( vsSCE) by single sweep oscillopolarography. The electrochemical behavior of the product was investigated by single sweep oscillopolarography and cyclic voltammetry. The experimental conditions for the measurement were optimized and the scavenging activity of some flavonoids on hydroxyl radicals was studied.

A new simple and sensitive fluorometric method for the determination of hydroxyl radical and its application.

A simple and sensitive fluorometric method to detect the hydroxyl radical is described. This method employs the reaction between OH and dimethyl sulfoxide (DMSO) to generate quantitatively formaldehyde, which then reacts with ammonia and 1,3-cyclohexanedione (CHD) at pH 4.5. The product produces the characteristic fluorescence with its excitation and emission wavelength at 400.4 and 452.3 nm, respectively. The quantitative analysis of hydroxyl radical can be done through the determination of the fluorescence intensity. By the developed method, the scavenging abilities of some amino acids and flavonoids on hydroxyl radical are studied.