Removal of lipopolysaccharide and reactive oxygen species using sialic acid immobilized polysulfone dialyzer

Sialic acid (N‐acetylneuraminic acid, NANA) was covalently immobilized onto the surface of a polysulfone (PSF) hollow fiber membrane. Prior to the immobilization, the surface of PSF was treated with ozone, followed by grafting with acrylic acid, and then the esterification of NANA. The surface concentration of NANA was determined by 2‐thiobarbituric acid (TBA) test. Hemocompatibility, the capability of suppressing oxidative stress, and clearance of lipopolysaccharide (LPS) from the resulting hollow fiber membrane were evaluated. The results show that by immobilizing NANA onto PSF hollow fiber, the adhesion of platelet was reduced, while both APTT and PT were little affected. Furthermore, oxidative stress was suppressed by NANA‐immobilized PSF hollow fibers. The level of LPS was also greatly reduced. Copyright © 2009 John Wiley & Sons, Ltd.     

Fast Determination of Clenbuterol and Salbutamol in Feed and Meat Products Based on Miniaturized Capillary Electrophoresis with Amperometric Detection

The fast separation capability of a novel miniaturized capillary electrophoresis with an amperometric detection (μCE‐AD) system was demonstrated by determining clenbuterol and salbutamol in real samples. The effects of several factors such as the acidity and concentration of the running buffer, the separation voltage, the applied potential and the injection time on CE‐AD were examined and optimized. Under the optimum conditions, the two β‐agonists could be baseline separated within 60 s at a separation voltage of 2 kV in a 90 mmol/L H₃BO₃‐Na₂B₄O₇ running buffer (pH 7.4), which was not interfered by ascorbic acid and uric acid. Highly linear response was obtained for above compounds over three orders of magnitude with detection limits ranging from 1.20×10^?7 to 6.50×10^?8 mol/L (S/N=3). This method was successfully used in the analysis of feed and meat products with relatively simple extraction procedures.     

Comparative Study of the Determination of Parabens in Shampoos by Liquid Chromatography with Amperometric and Coulometric Detection

The simultaneous determination of four para‐hydroxybenzoic acid esters (parabens) in shampoos was studied by liquid chromatography (LC) with amperometric (LC‐AD) and coulometric (LC‐CD) detection. The parabens were separated on an ODS C18 reversed column by isocratic elution with a mobile phase based on methanol‐0.1 M acetic acid (60 : 40%, v/v) with 0.02 M NaClO₄ at a flow rate of 0.8 mL min^?1. The limit of detection (S/N>3) for the analytes was in the 15–25 pg (injected mass) range at an applied potential of 1.20 V vs. Ag/AgCl using the LC‐AD and in the 2–3 pg range at a potential of 0.790 V vs. Pd using the LC‐CD. The peak ratio of the internal standard peak (IS: 4‐hydroxybenzoic acid sec‐butyl ester) versus the analyte peak was found to be related to the amount injected from 0.1 ng to 100ng (r=0.996–0.999) with the LC‐AD and from 0.050 ng to 100 ng range (r=0.999–1.000) with the LC‐CD. The relative standard deviation (RSD, n=10) was comprised between 1.8 to 3.5% by LC‐AD ( 5 ng injected) and between 2.0 to 2.4% by LC‐CD (0.5 ng injected). The determination of four most used parabens in ten different shampoos was successfully realized.     

The effect of covalent immobilization of sialic acid on the removal of lipopolysaccharide and reactive oxygen species for polyethylene terephthalate

Polyethylene terephthalate (PET) was aminolyzed with 1,6‐diaminohexane (DAH) and then sialic acid (NANA) was immobilized via amidation onto the surface. The surface concentration of NANA was determined by 2‐thiobarbituric acid (TBA) test. The hemocompatibility of the resulting PET fabrics was evaluated based on complete blood count (CBC), coagulating times, and protein adsorption. The ability to remove lipopolysaccharide (LPS) was also determined. In addition, the effect of contacting NANA‐immobilizing PET on the suppression of reactive oxygen species (ROS) production was measured by the chemiluminescence (CL) method. The results show that by immobilizing NANA onto PET, the adhesion of platelet (PLt) was reduced, and oxidative stress was suppressed. The level of LPS was also greatly reduced. Copyright © 2010 John Wiley & Sons, Ltd.     

Electrochemical Behavior and Electroanalytical Determination of Indole‐3‐Acetic Acid Phytohormone on a Boron‐Doped Diamond Electrode

In this work, a boron‐doped diamond (BDD) electrode was used for the electroanalytical determination of indole‐3‐acetic acid (IAA) phytohormone by square‐wave voltammetry. IAA yielded a well‐defined voltammetric response at +0.93 V (vs. Ag/AgCl) in Britton–Robinson buffer, pH 2.0. The process could be used to determine IAA in the concentration range of 5.0 to 50.0 µM (n=8, r=0.997), with a detection limit of 1.22 µM. The relative standard deviation of ten measurements was 2.09 % for 20.0 µM IAA. As an example, the practical applicability of BDD electrode was tested with the measurement of IAA in some plant seeds.     

Poly(pyridine‐3‐boronic acid)/Multiwalled Carbon Nanotubes Modified Glassy Carbon Electrodes for Simultaneous Determination of Ascorbic Acid, 3,4‐Dihydroxyphenylacetic Acid and Uric Acid

Poly(pyridine‐3‐boronic acid) (PPBA)/multiwalled carbon nanotubes (MWCNTs) composite modified glassy carbon electrode (GCE) was used for the simultaneous determination of ascorbic acid (AA), 3,4‐dihydroxyphenylacetic acid (DOPAC) and uric acid (UA). The anodic peaks for AA, DOPAC and UA at the PPBA/MWCNTs/GCE were well resolved in phosphate buffer solution (pH 7.4). The electrooxidation of AA, DOPAC and UA in the mixture solution was investigated. The peak currents increase with their concentrations increasing. The detection limits (S/N=3) of AA, DOPAC and UA are 5 µM, 3 µM and 0.6 µM, respectively.     

Metal‐binding Sites of N‐Acetylneuraminic Acid

Sialic acid represents a group of thirty derivates of neuraminic acid with various substituents at the amino residue and the alcoholic hydroxy groups. We analysed the behaviour of the tetracoordinated metal ions palladium(II) and silicon(IV) against the most important derivative N‐acetylneuraminic acid (NANA). The molecular structures were assigned by a combined ¹H, ¹³C and ²⁹Si NMR‐spectroscopic approach. Despite the presence of many different functional groups, the coordination chemistry of NANA with Pd^II follows established rules. Coordination via the N‐acetyl‐group – sterically impossible with Pd^II – was realised with Si^IV.     

Simultaneous measurement of methyl tert‐butyl ether and tert‐butyl alcohol in human serum by headspace solid‐phase microextraction gas chromatography–mass spectrometry

The abundant production of methyl tert‐butyl ether (MTBE) and its widespread use have led to an increase in the potential for human exposure. This work described a simple, fast, sensitive, reliable and low‐cost method for the simultaneous measurement of MTBE and its metabolite, tert‐butyl alcohol (TBA) in human serum by headspace solid‐phase microextraction gas chromatography–mass spectrometry. Extraction conditions were optimized and 40 °C, 10 min, 250 rpm and 0.3 g NaCl for a 1 mL sample were the optimal conditions. This method showed good analytical performance in terms of sensitivity with limits of detection in serum (1 mL) of 0.03 µg/L for MTBE and 0.05 µg/L for TBA, accuracy (mean recovery values) from 75.8% to 85.8%, precision (relative standard deviations) <10% and sample stability (biodegradation) <10% after 28 days. A verification experiment proved the reproducibility and stability of this method as well. Finally the method was used to detect 212 specimens, and the internal dose levels for MTBE in human serum were presented in China. Copyright © 2015 John Wiley & Sons, Ltd.     

Determination of amino acid neurotransmitters in rat hippocampi by HPLC‐UV using NBD‐F as a derivative

A simple, rapid and accurate high‐performance liquid chromatography method with ultraviolet–visible detection was developed for the determination of five amino acid neurotransmitters – aspartate, glutamic acid, glycine, taurine and γ‐aminobutyric acid – in rat hippocampi with pre‐column derivatization with 4‐fluoro‐7‐nitrobenzofurazan. Several conditions which influenced derivatization and separation, such as pH, temperature, acetonitrile percentage mobile phase and flow rate, were optimized to obtain a suitable protocol for amino acids quantification in samples. The separation of the five neurotransmitter derivatives was performed on a C₁₈ column using a mobile phase consisting of phosphate buffer (0.02 mol/L, pH 6.0)–acetonitrile (84:16, v/v) at a flow rate of 1.0 mL/min with the column temperature at 30°C. The detection wavelength was 472 nm. Without gradient elution, the five neurotransmitter derivatives were completely separated within 15 min. The linear relation was good in the range from 0.50 to 500 µmol/L, and the correlation coefficients were ≥0.999. Intra‐day precision was between 1.8 and 3.2%, and inter‐day precision was between 2.4 and 4.7%. The limits of detection (signal‐to‐noise ratio 3) were from 0.02 to 0.15 µmol/L. The established method was used to determine amino acid neurotransmitters in rat hippocampi with satisfactory recoveries varying from 94.9 to 105.2%. Copyright © 2013 John Wiley & Sons, Ltd.     

Highly Sensitive Nitric Oxide Sensing Using Three‐Dimensional Graphene/Ionic Liquid Nanocomposite

A nanocomposite gel with a uniform porous structure and well‐controlled compositions prepared by mixing three‐dimensional graphene material with an ionic liquid, 1‐butyl‐3‐methylimidazolium hexafluorophosphate, is used for nitric oxide detection. It shows a fast response of less than 4 seconds, an excellent sensitivity of 11.2 µA cm⁻² (µmol/L)⁻¹ and an extremely low detection limit of 16 nM with a signal‐to‐noise ratio of 3 (S/N=3), a performance superior to that of reported works based on carbon nanotubes and nanoparticles. The high sensitivity is attributed to the large electroactive surface area of the graphene gel nanocomposite towards nitric oxide oxidation. The electrochemical behavior of the gel nanocomposite is investigated and explained.     

Analysis of 11-nor-Δ(9) -tetrahydrocannabinol-9-carboxylic acid and its glucuronide in urine by capillary electrophoresis/mass spectrometry

Δ⁹‐Tetrahydrocannabinol is the primary psychoactive component in cannabis, one of the most commonly used illicit drugs in the world. This paper describes a simple and rapid method for direct analysis of major metabolites of Δ⁹‐tetrahydrocannabinol; 11‐nor‐Δ⁹‐tetrahydrocannabinol‐9‐carboxylic acid and its glucuronide in urine by capillary electrophoresis/mass spectrometry. The only pretreatment needed for a urine sample was dilution with methanol containing an internal standard and centrifugation. Electrophoresis was carried out in an untreated fused‐silica capillary (50 µm i.d. × 85 cm) filled with 40 m m ammonium formate (pH 6.4). An analysis could be completed within 10 min. For both compounds, the assay was linear over the range 0.1 ? 10 µg/mL in urine with correlation coefficients (r²) > 0.99 and the limit of detection was 0.5 pg (10 nL injection). The detection yields and reproducibilities were determined at three different concentrations (0.1, 0.5 and 2 µg/mL in urine). The mean detection yields were 60 ? 99%. The intra‐ and inter‐day relative standard deviations of migration times were 0.063 ? 0.19 and 0.18 ? 0.36%, and those of peak areas were 4.2 ? 18 and 5.9 ? 25%, respectively. The proposed method successfully analyzed the urine samples of cannabis users. Copyright © 2012 John Wiley & Sons, Ltd.     

Quantification of γ-aminobutyric acid in the heads of houseflies (Musca domestica) and diamondback moths (Plutella xylostella (L.)), using capillary electrophoresis with laser-induced fluorescence detection

A novel method was developed for quantifying the levels of γ‐aminobutyric acid (GABA) in the heads of houseflies (Musca domestica) and diamondback moths (Plutella xylostella (L.)), using capillary electrophoresis with laser‐induced fluorescence detection (CE‐LIF). The GABA in sample was derivatized with 4‐chloro‐7‐nitro‐2,1,3‐benzoxadiazole (NBD‐Cl) prior to CE‐LIF analysis. In total, 32 mmol/L borate buffer, at pH 9.2 and containing 5.3 mmol/L β‐cyclodextrin (β‐CD) and 10.4 mmol/L sodium dodecyl sulfate (SDS), was determined to be the optimum CE background electrolyte (BGE) for GABA analysis. The detection limit of GABA was 0.016 μmol/L. The relative standard deviations (RSDs) of the migration time and peak area of GABA were 1.78 and 4.93%, respectively. The average recoveries of 0.97, 3.88, and 5.83 μmol/L of GABA, each added to the head sample of housefly, ranged from 88.9 to 110.5%. This method is simple and applicable to GABA assays of the heads of insects. With this newly developed CE‐LIF method, the amounts of GABA in the heads of houseflies (M. domestica) and diamondback moths (P. xylostella (L.)) were measured. The results are relevant to the understandings of some insecticides and insecticide‐resistance mechanisms in pests.     

Quantification of malondialdehyde by HPLC‐FL – application to various biological samples

Malondialdehyde (MDA) is stabile product of lipid peroxidation (LPO), and therefore MDA is frequently used as a biomarker of LPO. To determine MDA level in various biological samples (human plasma, fish liver tissue and cells in culture), we used an HPLC method with fluorescent detection based on 2‐thiobarbituric acid (TBA) assay. The method was validated by the use of spiked pooled plasma samples. In tested concentration range (0.15–3.0 µmol/L) the method was linear (R² = 0.9963), the between‐day variability (coefficient of variations, CVs) was between 4.7 and 7.6%, the within‐day variability CVs was between 2.6 and 6.4% and recovery was between 91.2 and 107.6%. The level of MDA in human plasma (healthy male, non‐smokers, 46.3 ± 4.7 years; N = 38) was 2.2 ± 1.4 µmol/L; that in liver tissue of common carp (Cyprinus carpio; N = 12) was 0.02 ± 0.004 µmol/g tissue, and in cultured cells (human laryngeal carcinoma cells; N = 10) it was 0.18 ± 0.02 nmol/mg proteins. The HPLC‐FL method is rapid, accurate and reliable to follow the extent of LPO in various biological samples, particularly in samples in which a low level of MDA is expected, such as cells in culture. Owing to the rapid analytical process and run time, it can be used for routine analysis of MDA in clinical laboratory. Copyright © 2014 John Wiley & Sons, Ltd.     

Comparative metabolite profiling of carboxylic acids in rat urine by CE‐ESI MS/MS through positively pre‐charged and 2H‐coded derivatization

A new approach to the selective comparative metabolite profiling of carboxylic acids in rat urine was established using CE‐MS and a method for positively pre‐charged and ²H‐coded derivatization. Novel derivatizing reagents, N‐alkyl‐4‐aminomethyl‐pyridinum iodide (alkyl=butyl, butyl‐d9 or hexyl), containing quaternary amine and stable‐isotope atoms (deuterium), were introduced for the derivatization of carboxylic acids. CE separation in positive polarity showed high reproducibility (0.99–1.32% RSD of migration time) and eliminated problems with capillary coating known in CE‐MS anion analyses. Essentially complete ionization and increased hydrophobicity after the derivatization also enhanced MS detection sensitivity (e.g. formic acid was detected at 0.5 pg). Simultaneous derivatization of one sample using two structurally similar reagents, N‐butyl‐4‐aminomethyl‐pyridinum iodide (BAMP) and N‐hexyl‐4‐aminomethyl‐pyridinum iodide, provided additional information for recognizing a carboxylic acid in an unknown sample. Moreover, characteristic fragmentation acquired by online CE‐MS/MS allowed for identification and categorization of carboxylic acids. Applying this method on rat urine, we found 59 ions matching the characteristic patterns of carboxylic acids. From these 59, 32 ions were positively identified and confirmed with standards. For comparative analysis, 24 standard carboxylic acids were derivatized by chemically identical but isotopically distinct BAMP and N‐butyl‐d9‐4‐aminomethyl‐pyridinium iodide, and their derivatization limits and linearity ranges were determined. Comparative analysis was also performed on two individual urine samples derivatized with BAMP and N‐butyl‐d9‐4‐aminomethyl‐pyridinium iodide. The metabolite profiling variation between these two samples was clearly visualized.     

Asymmetric Synthesis of All Four Isomers of an Unusual Heterocycle‐Containing Amino Acid: 2‐Amino‐3‐furan‐2‐yl‐pentanoic Acid

All four isomers of a novel β‐branched unusual amino acid were designed and synthesized with high stereoselectivity (>90% de) and in 33% –44% overall yields by the use of 4(R/S)‐5,5‐dimethyl‐4‐phenyl‐oxazolidin‐2‐one as the chiral auxiliary via asymmetric 1,4‐Michael addition, direct or indirect azidation, hydrolysis and hydrogenation reactions.     

HPLC quantification of 5‐hydroxyeicosatetraenoic acid in human lung cancer tissues

A simple and cost‐effective HPLC method was established for quantification of 5‐hydroxyeicosatetraenoic acid (5‐HETE) in human lung cancer tissues. 5‐HETE from 27 patients' lung cancer tissues were extracted by solid‐phase extraction and analyzed on a Waters Symmetry C₁₈ column (4.6 × 250 mm, 5 µm) with a mobile phase consisting of methanol, 10 mm ammonium acetate, and 1 m acetic acid (70:30:0.1, v:v:v) at a flow rate of 1.0 mL/min. The UV detection wavelength was set at 240 nm. The calibration curve was linear within the concentration range from 10 to 1000 ng/mL (r² > 0.999, n = 7), the limit of detection was 1.0 ng/mL and the limit of quantitation was 10.0 ng/mL for a 100 µL injection. The relative error (%) for intra‐day accuracy was from 93.14 to 112.50% and the RSD (%) for intra‐day precision was from 0.21 to 2.60% over the concentration range 10–1000 ng/mL. By applying this method, amounts of 5‐HETE were quantitated in human lung cancer tissues from 27 human subjects. The established HPLC method was validated to be a simple, reliable and cost‐effective procedure that can be applied to conduct translational characterization of 5‐HETE in human lung cancer tissues. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and application of boronic acid‐functionalized magnetic adsorbent for sensitive analysis of salbutamol residues in pig tissues

Salbutamol (SAL) is the most widely used β₂‐agonist drug for asthma and chronic obstructive pulmonary patients, but it is also often abused as feed additive. In recent years, the abuse of SAL has led to a large number of food safety incidents. Therefore, the monitoring of SAL residues in animal products is very important. A highly selective boronate affinity magnetic adsorbent was synthesized and developed for detection of trace levels of SAL residues in pig tissue samples. The obtained Fe₃O₄@SiO₂@FPBA(4‐formylphenylboronic acid) magnetic adsorbent showed good adsorption ability to catechol and SAL, and then it was successfully applied as special magnetic solid‐phase phase extraction adsorbent coupled with high‐performance liquid chromatography (HPLC) for simultaneous isolation and determination of cis‐diol compounds. The binding capacity of catechol and SAL reached 96 and 50 µmol/g, respectively. The method was successfully established for the detection of trace levels of SAL in pig tissue samples. The linear range extended from 0.32 to 800 µg/kg (R² = 0.9994). The limit of detection of SAL was 0.19 µg/kg. The recoveries were satisfactory (89.5–108.0%) at three spiked levels with RSD between 2.1 and 11.3%. These results indicated that the method has potential for enrichment and detection of trace levels of SAL residual in animal food products. Copyright © 2015 John Wiley & Sons, Ltd.     

Nonenzymatic Hydrogen Peroxide Electrochemical Sensor Based on Au‐HS/SO3H‐PMO (Et) Nanocomposite

A newly nonenzymatic sensor for hydrogen peroxide (H₂O₂) based on the (Au‐HS/SO₃H‐PMO (Et)) nanocomposite is demonstrated. The electrochemical properties of the as‐prepared nanocomposite were studied. It displayed an excellent performance towards H₂O₂ sensing in the linear response range from 0.20 µM to 4.30 mM (R=0.9999) with a sensitivity of 6.35×10² µA µM^?1 cm^?2 and a low detection limit of 0.0499 µM. Furthermore, it was not affected by electroactive interference species. These features proved that the modified electrode was suitable for determination of H₂O₂.     

Chemiluminometric and Fluorimetric Determination of Folic Acid

Abstract

Folic acid was found to inhibit the chemiluminogenic reaction of N‐bromosuccinimide with dichlorofluorescein in alkaline medium. The analyte has also been determined after generation of a fluorescing compound by the action of hexacyanoferrate(III) or N‐bromosuccinimide in alkaline medium. Both procedures were further investigated and an attempt to propose the corresponding mechanisms was also made. The chemiluminogenic procedure allows the determination of folic acid within the range 6.0 to 114 µg/ml with limits of detection and quantification equal to 2.0 and 6.0 µg/ml, respectively and rsd at 11.4 µg/ml equal to 1.0% (n=12) while the fluorogenic procedure allows the determination of folic acid within the range 0.022–1.10 µg/ml with limits of detection and quantification equal to 0.002 and 0.005 µg/ml, respectively and rsd at 0.022 µg/ml equal to 0.7 (n=10). The methods are compared and successfully applied to commercial preparations containing folic acid.     

Simultaneous determination of corosolic acid and euscaphic acid in the plasma of normal and diabetic rat after oral administration of extract of Potentilla discolor Bunge by high‐performance liquid chromatography/electrospray ionization mass spectrometry

Potentilla discolor Bunge has been used for diabetes in China for a long time. Corosolic acid (CA) and euscaphic acid (EA), with significant anti‐diabetic activity, are two major triterpenoids in P. discolor. In this study, a specific, sensitive and convenient LC‐MS method has been developed for simultaneous determination of CA and EA in the plasma of normal and diabetic rats after oral administration of the extract of P. discolor. The chromatographic separation was achieved using an Alltima C₁₈ column (53 × 7.0 mm, i.d., 3 µm) with a mobile phase composed of 0.1% formic acid water and 0.1% formic acid acetonitrile at a flow rate of 1.0 mL/min. The detection was performed by MS with electrospray ionization interface in negative selected ion monitoring mode. All the validation data, such as specificity, linearity (r² > 0.9991 within 0.025–10.0 µg/mL), lower limit of quantitation (2.5 ng/mL), precision (intra‐ and inter‐day <14.7%), accuracy (<15.0%), recovery (85.7–110.8%) and stability were determined and all of them were within the required limits. This method was successfully applied for the evaluation of the pharmacokinetic behaviors of these two compounds in the plasma of normal and diabetic rats. Copyright © 2013 John Wiley & Sons, Ltd.