Determination of medroxyprogesterone acetate residues by CE immunoassay with chemiluminescence detection

A rapid and simple method is developed for the determination of medroxyprogesterone acetate (MPA) by CE immunoassay with chemiluminescence (CL). This method is based on the competitive reactions between horseradish peroxidase (HRP)-labeled MPA (MPA-HRP) and free MPA with anti-MPA antiserum. The influencing factors on the electrophoresis and CL detection were studied completely and the optimal conditions of separation and determination were obtained. The linear range was 2.0-50 nmol/L and the LOD for MPA was 0.9 nmol/L. The present method was applied to the analysis of pork tissues.     

Classical solutions to relativistic Burgers equations in FLRW space-times

We are interested in the classical solutions to the Cauchy problem of relativistic Burgers equations evolving in Friedmann-Lemat?tre-Robertson-Walker(FLRW)space-times,which are spatially homogeneous,isotropic expanding or contracting universes.In such kind of space-times,we first derive the relativistic Burgers equations from the relativistic Euler equations by letting the pressure be zero.Then we can show the global existence of the classical solution to the derived equation in the accelerated expanding space-times with small initial data by the method of characteristics when the spacial dimension n=1 and the energy estimate when n 2,respectively.Furthermore,we can also show the lifespan of the classical solution by similar methods when the expansion rate of the space-times is not so fast.     

高功率准连续激光二极管抽运的Nd：YVO4激光器

对高功率准连续激光二极管端面抽运的Nd:YVO4固体激光器进行了实验研究。研究了抽运功率、温度、重复率及输出镜的透过率对激光器输出功率的影响。当激光二极管重复率达到720Hz、抽动功率33.2W时,激光输出最大平均功率为11W。     

Determination of PEGylation homogeneity of polyethylene glycol-modified canine uricase

Polyethylene glycol-modified canine uricase (PEG-UHC) was prepared by modifying the ε-amino group of lysine residues on the canine uricase (UHC) protein to near-saturation with 5 kDa monomethoxyl-polyethylene glycol succinimide (mPEG-SPA-5k). In order to accurately determine the PEGylation uniformity of PEG-UHC, CZE, 3–8% gradient gel SDS-PAGE, and imaging CIEF (iCIEF) analyses were compared. CZE could not effectively separate PEG-UHC proteins with different degrees of modification, 3–8% gradient gel SDS-PAGE could separate PEG-UHC into seven gel bands; however, most of the gel bands were smeared or blurred, and the separation of PEG-UHC samples by iCIEF was significantly better than that by 3–8% gradient gel SDS-PAGE. Under denatured conditions, iCIEF separated 12 pI peaks, and could also accurately quantify the relative monomer PEG-UHC content. More than 85% of the total monomeric PEG-UHC was conjugated with 7–12 PEG molecules; of this 85%, approximately 40% was conjugated with 9–10 PEG molecules. These results demonstrated that iCIEF exhibits good potential for determining the PEGylation homogeneity of PEGylated protein drugs.     

Kinetic and mechanistic studies on the oxidation of pyrrolidine by bis(hydrogenperiodato)argentate(III) complex anion

The kinetics of oxidation of pyrrolidine by bis(hydrogenperiodato)argentate(III) complex anion ([Ag(HIO₆)₂]^5?) was studied in alkaline medium, with reaction temperatures in the range of 15.0–30.0 °C. The experiments indicated that the oxidation follows an overall second-order reaction, being first-order in both Ag(III) and pyrrolidine. The observed second-order rate constants, k′, decreased with increasing [IO₄ ^?] but increased slightly with increasing [OH^?]. The influence of ionic strength on the reaction rate was also investigated. The oxidation resulted in oxidative deamination of pyrrolidine, giving 4-hydroxybutyrate as the product. A reaction mechanism is proposed which includes an equilibrium between [Ag(HIO₆)₂]^5? and [Ag(HIO₆)₂(OH)(H₂O)]^2?; these two Ag(III) species are reduced by pyrrolidine in parallel rate-determining steps. The rate equation derived from the proposed mechanism can explain the experimental observations. The rate constants of the rate-determining steps, together with the associated activation parameters, were calculated accordingly.     

Hydrothermal conversion of cellulose into lactic acid with nickel catalyst

Utilization of biomass has become a major topic of research around the world. One promising aspect of utilization is production of lactic acid from carbohydrate biomass. Our previous study showed that lactic acid can be formed from glucose and cellulose by alkaline hydrothermal reactions, but the yield of lactic acid was low, particular for cellulose. In this study, an efficient method for producing lactic acid from cellulose under hydrothermal conditions with NaOH in the presence of nickel was developed. Experiments were conducted in a batch reactor at 300 °C for 1?C4 min. Results showed that nickel could promote the yield of lactic acid from cellulose. The highest yield of 34.07% was obtained by adding 0.5 mmol nickel using 2.5 M NaOH solution at 300 °C for 1 min.     

Preparation and evaluation of hydrophilic C18 monolithic sorbents for enhanced polar compound retention in liquid chromatography and solid phase extraction

Hydrophilic C18 monolithic polymer sorbents were synthesized for use in solid phase extraction (SPE) and in capillary liquid chromatography (LC). The approach involved incorporating both hydrophobic and hydrophilic monomers into a monolithic material, by copolymerization of stearyl methacrylate (SMA), poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) and ethylene dimethacrylate (EDMA) in the presence of selected porogens, to produce translucent mesoporous monolithic materials in bulk (SPE) or white macroporous monoliths inside fused silica capillary columns (capillary LC). A capillary column containing one of the hydrophilic C18 monoliths (i.e. poly(SMA-co-PEGMEMA-co-EDMA) with 15% (w/w) PEGMEMA) demonstrated nearly 35% reduction in retention of polycyclic aromatic compounds and greater than 40% increase in retention of phenols compared to a hydrophobic C18 monolithic column. In addition, the hydrophilic monolith demonstrated significantly improved resolution of phenols. Similar monolithic materials prepared in bulk were ground and sieved to obtain 45-65 μm particles with desired rigidity for SPE. To achieve optimum extraction performance for phenols, several parameters, including sample pH and volume, and eluent type and volume, were investigated. Under optimized experimental conditions, the method demonstrated good sensitivity (1.6 ng/mL LOD) and linearity (R(2)>0.97 for 10-200 ng/mL). Again, incorporation of 15% (w/w) PEGMEMA in the monolith increased the extraction efficiency of phenols in water from approximately 20% to 67-92% compared to a hydrophobic C18 monolithic material. Increased wettability of the sorbent by the aqueous sample matrix and the presence of hydrogen-bonding interactions are responsible for the improved retention of polar compounds.     

Tailoring Morphology of PVDF-HFP Membrane via One-step Reactive Vapor Induced Phase Separation for Efficient Oil-Water Separation

Poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP) receives increasing attention in membrane separation field based on its advantages such as high mechanical strength, thermal and chemical stability. However, controlling the microporous structure is still challenging.In this work, we attempted to tailor the morphology of PVDF-HFP membrane via a one-step reactive vapor induced phase separation method.Namely, PVDF-HFP was dissolved in a volatile solvent and then was cast in an ammonia water vapor atmosphere. After complete evaporation of solvent, membranes with adjustable porous structure were prepared, and the microstructures of the membranes were analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction characterizations. Based on the results, a mechanism of dehydrofluorination induced cross-linking of PVDF-HFP has been suggested to understand the morphology tailoring.To our knowledge, this is the first report of one-step reactive vapor induced phase separation strategy to tailor morphology of PVDF-HFP membrane. In addition, the membranes prepared in the ammonia water vapor exhibited enhanced mechanical strength and achieved satisfactory separation efficiency for water-in-oil emulsions, suggesting promising potential.     

Prediction of soil organic carbon partition coefficients by soil column liquid chromatography

To avoid the limitation of the widely used prediction methods of soil organic carbon partition coefficients (KOC) from hydrophobic parameters, e.g., the n-octanol/water partition coefficients (KOW) and the reversed phase high performance liquid chromatographic (RP-HPLC) retention factors, the soil column liquid chromatographic (SCLC) method was developed for KOC prediction. The real soils were used as the packing materials of RP-HPLC columns, and the correlations between the retention factors of organic compounds on soil columns (ksoil) and KOC measured by batch equilibrium method were studied. Good correlations were achieved between ksoil and KOC for three types of soils with different properties. All the square of the correlation coefficients (R2) of the linear regression between log ksoil and log KOC were higher than 0.89 with standard deviations of less than 0.21. In addition, the prediction of KOC from KOW and the RP-HPLC retention factors on cyanopropyl (CN) stationary phase (kCN) was comparatively evaluated for the three types of soils. The results show that the prediction of KOC from kCN and KOW is only applicable to some specific types of soils. The results obtained in the present study proved that the SCLC method is appropriate for the KOC prediction for different types of soils, however the applicability of using hydrophobic parameters to predict KOC largely depends on the properties of soil concerned.     

Determination of organophosphate and carbamate pesticides based on enzyme inhibition using a pH-sensitive fluorescence probe

A flow injection system for the determination of organophosphate and carbamate pesticides is described. A sensitive fluorescence probe was synthesized and used as the pH indicator to detect the inhibition of the enzyme acetylcholinesterase (AChE). The percentage inhibition of enzyme activity is correlated to the pesticide concentration. Several parameters influencing the performance of the system are discussed. The detection limits of 3.5, 50, 12 and 25 μg/l for carbofuran, carbaryl, paraoxon and dichlorvos, in pure water, respectively were achieved with an incubation time of 10 min. A complete cycle of analysis, including incubation time, took 14 min. The detection system has been applied to the determination of carbofuran in spiked vegetable juices (Chinese cabbage and cole), achieving recovery values between 93.2 and 107% for Chinese cabbage juice and 108 and 118% for cole juice at the different concentration levels assayed.