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A convenient and green pre-processing method is presented for determining physiological targets and drugs in biological samples using nanofiber-packed solid-phase extraction instead of a traditional cartridge. Biological samples, including plasma (model target molecule is desloratadine), urine (catecholamines), and saliva (cortisol) were used to characterize sample pre-treatment. Nanofiber-based solid-phase extraction sufficiently isolated the compounds from the complex matrixes. The absolute extraction rates were between 52.3% and 85.7%. Because the nanofiber-packed solid-phase extraction cartridge is a small, lightweight, portable, convenient, and labor-saving device, this pre-processing method has great potential for further application.

The objective of this study was to compare the enrichment performanc of polystyrene-dithizone (PS-DZ) electrospun nanofibrous membrane with commercial cellulose acetate (CA) film for lead in air. Lead was analyzed by preconcentration on different membranes followed by digestion and analysis by Atomic Fluorescence Spectrometry. In comparison to CA film, the PS-DZ electrospun nanofibrous membrane exhibited a significant advantage in enrichment efficiency (about threefold increase). The result confirms that electrospun nanofibrous membrane can be a potential candidate for the sampling of metals in air.

Due to pipe-laying process changed for Offshore Oil 201 pipelay vessel requires to place sand blasting machine equipment in suite place, to meet the sand-blasting machine to complete the process of laying pipe work cycle which demands for subsea pipelines sandblasting, then the sand-blasting lifting equipment was designed. The equipment consists of a hydraulic lifting platform system, rail trolley system and control system. The experiments showed that the sand-blasting lifting equipment could securely connect with sand-blasting machine, the sand-blasting machine could be lift fast, installation fast in the suite place, meeting the production requirements.

The objective of this study was to research the performance of the electrospun polystyrene-acrylic resin composite nanofibre on the adsorption of gaseous aromatic compounds, such as benzene and chlorobenzene. The equilibrium adsorption amount of benzene was 254.3 μg mg-1, while the equilibrium adsorption amount of chlorobenzene was 2.5 μg mg-1. The dynamic adsorption of the two compounds onto the composite nanofibres was also studied. Comparing with the conventional adsorbent (Tenax-TA), the performace of this nanofibre was well as that of Tenax-TA. The results of comparison confirm that electrospun nanofibres can be a potential adsorbent for the sampling of gaseous aromatic compounds.

In order to detect the environmental pollutants in water sample with high sensitivity, an automatic method based on a combined preconcentration setup and flow injection system was developed. A novel packed fiber solid phase extraction (PFSPE) cartridge packed with electrospun nanofiber was first designed to adsorb environmental pollutants from water media in an online manner. Rhodamine B (RB) was selected as a model pollutant. Under the optimized conditions, a good linearity of wide range between 25-1000 ng mL-1 was achieved. The LOD was 7.5 ng mL-1. The method was applied to analysis RB in water samples with satisfactory results.

A novel micro-extraction procedure was developed through the use of an electrospun polymer nanofiber as a solid-phase extraction (SPE) sorbent to directly extract benzimidazoles in pork. The target compound was then monitored by a high performance liquid chromatography with ultraviolet detector (HPLC-UV) system. The eluted solvent was investigated meanwhile. Under the optimized conditions, a linear response for benzimidazoles over the range of 20-1000 ng mL−1 was achieved with the γ2 >0.99. The recoveries were in the range of 95.4%~101.2%. RSDs of intra-day and inter-day assays were 3.5%~6.3% and 5.7%~9.9%. The method is simple, sensitive, accurate and repeatable, which can be used for the determination of benzimidazoles in pork.

In recent years, many studies found that hair cortisol can serve as a good biomarker of chronic stress. A high-performance liquid chromatography-Fluorescence (HPLC-Flu) method for the determination of hair cortisol based on novel packed nanofiber solid-phase extraction (PFSPE) was established. The incubation solution of hair samples was extracted by the new type of PFSPE column. The column was eluted with 100 μL of ethanol, and then 230 μL of concentrated sulfuric acid was added into the eluant and retained for 2 min. The mixture of reactants and water was secondly extracted by the PFSPE column, in which the target compounds were desorbed with 50 μL of methanol directly. The detection limit of cortisol was 0.5 ng g −1 (signal-to-noise ratio of 3). The within-run and between-day precisions (RSD) were below 6.8% and 8.9%, and the average recovery of cortisol spiked into the hair samples was 88.9%. The method of pretreatment is simple, fast and green. Moreover, the established method can be used to determine the level of cortisol in hair samples, which is a simple, inexpensive determination method for applications in physiology, psychiatry, sports medicine, cognitive science, psychology and other areas of research.

A rapid and simple preconcentration step applying packed-fiber solid-phase extraction columns has been investigated to vitamin B 12 . The extraction performance of the new method was investigated preliminarily on vitamin functional drink. The analysis used a reversed-phase C 18 column, with a photo-diode array detector at 220 nm. The samples were preconcentrated with packed-fiber solid-phase extraction columns. Good linearity was observed in vitamin functional drink. The repeatability of extraction performance, expressed as relative standard deviations, was from 3.5% to 4.3%. The limit of detection (LOD) is 5 ng mL −1 (S/N = 3). Finally, the method had been applied for the determination of vitamin B 12 in vitamin functional drink.

An accurate, simple, and sensitive reversed-phase high-performance liquid chromatographic method, with loratadine as internal standard (IS) and UV detection at 286 nm, has been developed for deterination of cystine in human urine. The major innovations of the method include use of acrylonitrile to protect cysteine from oxidization to cystine, separation of cysteine, as the dansyl derivative, from cystine, and use of isocratic elution instead of gradient elution to reduce the time and cost of serial analysis. The mobile phase was 0.05 M sodium acetate–methanol, 35:65 (v/v), adjusted to pH 3.5 with 2.5 M citric acid, at a flow rate of 1.0 mL min−1. The retention times of cystine and the IS were 16.6 and 19.9 min, respectively. The limit of detection for cystine was 0.3 mg L−1. Extraction recovery of cystine was >85.6%. Intra-day and inter-day precision (RSD) for cystine were below 4.3 and 8.5%, respectively. There was no chromatographic interference from other α-amino acids present in mammalian proteins, or from other urine components. The calibration plot for the cystine derivative was linear in the range 1–500 mg L−1 and the correlation coefficient was 0.9992. The method was validated appropriately and successfully used for determination of cystine in human urine.

Nitroxoline (8-hydroxy-5-nitroquinoline) and the structural related compounds 8-hydroxyquine, 8-hydroxy-5,7-dinitroquinoline, and 8-hydroxy-5-nitrosoquinoline have been investigated by reversed-phase high-performance liquid chromatography on C18/ODS. Complete separation and symmetric, peaks were obtained by use of THF-methanol-water, 3∶3∶4, containing 10 mmol L−1 disodium ethylenediamine tetraacetic acid (EDTA) and 10 mmol L−1 citric acid in the water, as mobile phase. The pH and the concentration of EDTA in the mobile phase were found to be critical for eliminating tailing and for full separation. The calibration plot was linear for concentrations between 3.0 and 300 μg mL−1; the regression coefficient was 0.99996. Assay of the nitroxoline standard showed that recovery was from 99.3 to 102%, with a mean standard deviation for nitroxoline of 0.9%. The method is suitable for quality control of nitroxoline.

For the first time, electrospun composite nanofibers comprising polymeric crown ether with polystyrene (PCE-PS) have been used for the selective extraction of catecholamines - dopamine (DA), norepinephrine (NE) and epinephrine (E) - prior to their analysis by high-performance liquid chromatography-electrochemical detection. Using a minicartridge packed with PCE-PS composite nanofibers, the target compounds were extracted effectively from urine samples to which diphenylborinic acid 2-aminoethyl ester was added as a complexing reagent. The extracted catecholamines could be liberated from the fiber by the addition of acetic acid. A good linearity was observed for catecholamines in the range of 2.0-200 ng mL(-1) (NE, E and DA). The detection limits of catecholamines (signal-to-noise ratio = 3) were 0.5 ng mL(-1) (NE), 0.2 ng mL(-1) (E) and 0.2 ng mL(-1) (DA), respectively. Under the optimized conditions, the absolute recoveries of the above three catecholamines were 90.6% (NE), 88.5% (E) and 94.5% (DA). The repeatability of extraction performance was from 5.4 to 9.2% (expressed as relative standard deviation). Our results indicate that the proposed method could be used for the determination of NE, E and DA in urine.

Due to the limitation of the hole injection, p-type doping is essential to improve the performance of InGaN/GaN multiple quantum well light-emitting diodes (LEDs). In this work, we propose and show a depletion-region Mg-doping method. Here we systematically analyze the effectiveness of different Mg-doping profiles ranging from the electron blocking layer to the active region. Numerical computations show that the Mg-doping decreases the valence band barrier for holes and thus enhances the hole transportation. The proposed depletion-region Mg-doping approach also increases the barrier height for electrons, which leads to a reduced electron overflow, while increasing the hole concentration in the p-GaN layer. Experimentally measured external quantum efficiency indicates that Mg-doping position is vitally important. The doping in or adjacent to the quantum well degrades the LED performance due to Mg diffusion, increasing the corresponding nonradiative recombination, which is well supported by the measured carrier lifetimes. The experimental results are well numerically reproduced by modifying the nonradiative recombination lifetimes, which further validate the effectiveness of our approach. NRF (Natl Research Foundation, S’pore) ASTAR (Agency for Sci., Tech. and Research, S’pore) Published version

Laser lift-off technique was employed to carry out transfer of prefabricated InGaN multiple-quantum-well light-emitting diodes (LEDs) from sapphire onto Cu substrate. Silver epoxy was used as the bonding material. Characterization results showed tremendous device improvements in terms of maximum allowable current, light output power, and reliability from the use of conductive Cu substrate. LEDs on Cu could withstand a maximum current of 530 mA before breakdown while those on sapphire could only withstand 350 mA. At 40 mA, light output power of LEDs on sapphire and Cu was 0.74 and 0.95 mW, respectively. In addition, reliability test at constant current of 300 mA showed improvement in light output power for LEDs on Cu whereas LEDs on sapphire suffered deterioration with time.

To develop a high performance liquid chromatography (HPLC) for detection of monoamine neurotransmitters and its metabolites after pre-column derivatization with dansyl chloride.The C(18) chromatograph column (150 mm×4.6 mm×5 µm) was selected for detection, and derived by dansyl chloride (10 mg/ml) under the condition of 50°C water bath by pH11 buffer solution. 20 µl acetic acid acetone solution (1.0 mol/L) was then mixed in for termination of the reaction. Then the solution was cooling to room temperature, 0.1 mol/L acetic acid zinc-acetonitrile-tetrahydrofuran solution was adopted for mobile phrase, with the volume ratio at 62:35:3. The flow rate was 1.0 ml/min between 0-10 min, 2.0 ml/min between 10-35 min. The ultraviolet detection wavelength was 286 nm. The above method separately detected monoamine neurotransmitters and its metabolites and evaluated the limit of detection, accurate degree and accuracy degree.The linear relations between each component was good in the range of 1 - 20 µg/ml (r = 0.999). The lowest detection limit of norepinephrine, dopamine, 5-hydroxytryptamine and the metabolites 3-methoxy-4-benzoglycols, homovanillic acid and 5-heteroauxin were separately 0.60, 0.80, 0.41, 0.21, 0.19 and 0.1 µg/ml; while the average recovery rates were between 78.5% - 95.9%, and the relative standard deviation (RSD) was 6.62%, 7.64%, 2.98%, 3.60%, 5.09% and 3.09%, respectively. In the process of selection and optimization of the chromatographic conditions, we observed the importance of metal ions to discretion, and discussed the temperature, pH of the buffer solution and dosage of dansyl chloride in derivation. Under the above conditions, the reaction was perfect, and the baseline of the detected materials thoroughly separated.The method to detect monoamine neurotransmitters and its metabolites by HPLC and pre-column derivatization with dansyl chloride was established; and this method could provide reference for the detection of polyamine by HPLC.