Assay of Serum Glutamic-Oxaloacetic Transaminase Using Malate Dehydrogenase Preparation Obtained from Streptomyces aureofaciens

Abstract

A modified spectrophotometric method for serum glutamic-oxaloacetic transaminase (SGOT) assay was developed. A crude cell-free extract from Streptomyces aureofaciens which showed a high level of malate dehydrogenase (MDH) activity (E.C. 1.1.1.37) was used as the enzymatic indicator. The lyophilized microbial preparation was used without previous purification and was quite stable under refrigeration for one year. Serum sample assays using both the method utilizing the crude cell extract and an enzymatic commercial kit showed good correlation.     

Development and validation of an HPLC method for tetracycline‐related USP monographs

A novel reversed‐phase HPLC method was developed and validated for the assay of tetracycline hydrochloride and the limit of 4‐epianhydrotetracycline hydrochloride impurity in tetracycline hydrochloride commercial bulk and pharmaceutical products. The method employed L1 (3 µm, 150 × 4.6 mm) columns, a mobile phase of 0.1% phosphoric acid and acetonitrile at a flow rate of 1.0 mL/min, and detection at 280 nm. The separation was performed in HPLC gradient mode. Forced degradation studies showed that tetracycline eluted as a spectrally pure peak and was well resolved from its degradation products. The fast degradation of tetracycline hydrochloride and 4‐epianhydrotetracycline hydrochloride in solution was retarded by controlling the autosampler temperature at 4 °C and using 0.1% H₃PO₄ as diluent. The robustness of the method was tested starting with the maximum variations allowed in the US Pharmacopeia (USP) general chapter Chromatography <621>. The method was linear over the range 80–120% of the assay concentration (0.1 mg/mL) for tetracycline hydrochloride and 50–150% of the acceptance criteria specified in the individual USP monographs for 4‐epianhydrotetracycline hydrochloride. The limit of quantification for 4‐epianhydrotetracycline hydrochloride was 0.1 µg/mL, 20 times lower than the acceptance criteria. The method was specific, precise, accurate and robust. Copyright © 2014 John Wiley & Sons, Ltd.     

Quantitative Analysis of Tetracycline by High Performance Liquid Chromatography on Polystyrene-Divinylbenzene Packing Materials

Abstract

Isocratic high-performance liquid chromatography on a poly(styrene-divinylbenzene) copolymer column allows the complete separation and resolution of tetracycline, 4-epitetracycline, anhydrotetracycline and 4-epianhydrotetracycline. A fermentation impurity, 2-acetyl-2-decarboxamidotetracycline is also resolved from tetracycline. The mobile phase combines tert.-butanol, water and phosphate buffer, tetrabutylammonium sulphate and sodium ethylenediaminetetraacetate at a pH of 9.0 for elution at a temperature of 60°. The method was used to analyse official standards and commercial samples.     

Quantitative analysis and pharmacokinetics study of tigecycline in human serum using a validated sensitive liquid chromatography with tandem mass spectrometry method

Tigecycline, a novel intravenously administered glycylcycline antibiotic, currently plays a key role in the management of complicated multiorganism infections. However, current liquid chromatography with tandem mass spectrometry methods briefly describe parameters and the only reported internal standard was sometimes difficult to obtain. In our study, an updated liquid chromatography with tandem mass spectrometry method for the quantitative analysis of tigecycline in human serum was developed. Sample preparation involved precipitation with 20% trichloroacetic acid. Chromatographic separation of tigecycline and tetracycline (internal standard) was achieved on a Hypersil GOLD C₁₈ column using gradient elution. The selected reaction monitoring transitions were performed at m/z 586.1→513.2 for tigecycline and m/z 445.1→410.2 for tetracycline. The assay was linear over the concentration range of 5–2000 ng/mL. The intra‐ and interday precisions at three concentration levels (10, 100, and 1600 ng/mL) were <15% and their accuracies were within the range of 95.1–106.1%. The mean recovery ranged from 94.3 to 105.6% and the matrix effect from 92.1 to 97.6%. Tigecycline was stable under all tested conditions. This validated method was successfully applied to a pharmacokinetic study in critically ill patients. The data demonstrated that our method allows quantification of tigecycline in serum in a quick and reliable manner for widespread application.     

RP-HPLC and NMR study of antioxidant flavonoids in extract from <Emphasis Type="Italic">Gentiana piasezkii</Emphasis>

A reversed-phase high performance liquid chromatography (RP-HPLC) separation with photodiode array detection (PDA) was developed for the simultaneous determination of five flavonoids, lutonarin (LO), saponarin (SA), isoorient (IO), 7-O-feruloylorientin (FO) and luteolin (LE) in the extract of Gentiana piasezkii, a popular forage grass, pharmaceutical and ornamental plant in China. The optimized method was achieved for the separation and detection of selected constituents, using acetonitrile-1% acetic acid as the mobile phase with gradient elution at a flow rate of 0.8 mL/min and 350 nm as the detection wavelength. The contents of the five flavonoids, i.e., LO, SA, IO, FO and LE in the plant of G. piasezkii were 0.1524, 0.0673, 0.300, 0.0552 and 0.0052%, respectively. The compounds possess similar structures and have been studied by nuclear magnetic resonance (NMR) spectroscopy.     

One-pot practical method for synthesis of functionalized 4H-chromen-5-one derivatives under catalyst and solvent-free conditions

Abstract

A facile and practical method was described for the synthesis of 4H-chromen-5-ones under catalyst- and solvent-free conditions by one-pot stirring of starting materials at 110?°C. The products were obtained by the reaction between cyclic 1,3-dicarbonyl compounds, aromatic aldehydes and (E)-N-methyl-1-(methylthio)-2-nitroethenamine (NMSM) in short duration with good to excellent yields. This simple and environmentally benign method eliminates the use of expensive, metallic and corrosive catalysts, hazardous organic solvents, and chromatographic separation.     

The use of load separation criterion and normalization method in ductile fracture characterization of thermoplastic polymers

Load separation is the theoretical basis for the single-specimen J-integral experiment and the incremental calculation of J-integral crack growth resistance (J-R) curves. This criterion has been experimentally studied in nongrowing crack records in several materials, and more recently a new method to extend the applicability to growing crack experiments has been proposed in testing steel. This article examines the applicability of the load separation criterion for evaluating ductile fracture mechanics parameters in rubber-modified polystyrenes and thermally treated polypropylene in the bending configuration. This criterion allows the load to be represented as the multiplication of two independent functions: a material deformation function and a crack geometry function. Its validity is evaluated with both stationary and growing crack experiments. η-factor calculation for smooth and side-grooved specimens was also tried using the simple method of Sharobeam and Landes, in order to identify material dependency. This article also investigates the applicability of the normalization method, based on the load separation criterion for evaluating J-R curves on PP and PS. A simple approach which combines a blunt notched and a precracked specimen experiment is proposed to determine the J-R curve of the materials studied. The resulting J-R curves are compared with multiple specimen results available in the literature for these materials. A good agreement between the J-R curves obtained from this simple method and from the multiple specimen technique was found. © 1996 John Wiley & Sons, Inc.     

Determination of Vitamin B12 in Multivitamin Tablets by High Performance Liquid Chromatography

Abstract

Two procedures for separation and determination of vitamin B₁₂ in multivitamin tablets by reversed phase high performance liquid chromatography are proposed. Sample preparation is very simple: tablets are dissolved in distilled water, centrifuged and filtered. The sample solution is directly applied in the sample loop injector and chromatograms are obtained with gradient elution using water-methanol and water-acetonitrile as solvents. The peak of vitamin B₁₂ from samples of B-complex tablets is well separated with the two procedures. For multivitamin tablets, however, only the procedure with water and methanol as solvents was good for separation and quantification of vitamin B₁₂. Both procedures were verified by the standard addition method and also compared to a previously developed method using electrothermal atomic absorption spectrometry for vitamin B₁₂ determination.     

Determination of flavonoids in the flowers of <Emphasis Type="Italic">Paulownia tomentosa</Emphasis> by high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) technique coupled with photodiode array (PDA) detection was developed for the simultaneous determination of four flavonoids, i.e. apigenin (AP), diplacone (DI), mimulone (MI) and 5,4′-dihydroxy-7,3′-dimethoxyflavanone (DDF) in extracts of the flowers of Paulownia tomentosa. The optimized method was proposed for the separation and detection of the selected constituents, using methanol-1% acetic acid as the mobile phase at a flow rate of 0.8 mL/min, 290 and 267 nm as the detection wavelengths. All the flavonoids showed good linearity in a relatively wide concentration range (r > 0.9999). The detection limits for the analytes ranged from 0.2 to 4.0 ng, at a signal-to-noise ratio of 3. Inter- and intra-assay accuracy and precision were all lower than 5.0%. The recovery of the method was 95.9–101.9%. Moreover, the optimized HPLC method was employed to analyze the flowers of Paulownia tomentosa.     

A simple way of recycling of homogeneous catalyst in Suzuki reaction

Abstract

A simple and practical method of recycling homogeneous catalysts in the Suzuki reaction using appropriate work up conditions is reported here. The commonly used and commercially available homogeneous catalysts 1 (Pd-100) dichlorobis(tri-phenylphosphine)palladium(II), 2 (Pd-106) dichloro[1,1′-bis(diphenylphosphino)ferrocene]palladium(II)-dichloromethane adduct, and 3 (Pd-118) 1,1′-bis(di-tert-butylphosphino)ferrocene]dichloropalladium(II) selected for our study and were recycled successfully for three times using simple acidic and basic work up conditions depending on the presence of amino or carboxylic acid functional group in the product.     

Simultaneous Determination of Oxytetra- cycline, Doxycycline, Tetracycline and Chlortetracycline in Tetracycline Antibiotics by High-Performance Liquid Chromatog- raphy with Fluorescence Detection

A simple, rapid and sensitive high-performance liquid chromatographic method with fluorescence detection for the simultaneous determination of oxytetracycline, doxycycline, tetracycline and chlortetracycline was developed, and successfully applied to the analysis of commercial tetracycline antibiotics. The separation was performed on a reverse-phase C₁₈ column with a gradient elution composed of methanol and sodium acetate buffer (containing disodium ethylenediaminetetraacetate and calcium chloride, pH 8.10) as the mobile phase, and fluorescence detection at 532 nm (excitation at 380 nm). The detection limits for oxytetracycline, doxycycline, tetracycline and chlortetracycline were 0.1, 0.5, 0.3 and 0.4 g L^–1, respectively. Data with respect to precision and accuracy were reported and discussed.     

Speciation analysis of chromium in natural water samples by electrothermal atomic absorbance spectrometry after separation/preconcentration with nanometer zirconium phosphate

A sensitive and simple method for the electrothermal atomic absorption spectrometry (ETAAS) determination of Cr(III) after separation/preconcentration on a micro-column packed with nanometer sized zirconium phosphate has been developed. Total chromium was determined after the reduction of Cr(VI) to Cr(III) by 10% (m/v) of aqueous ascorbic acid. The limit of detection for Cr(III) was 1.5 ng/L with an enrichment factor of 300. The static adsorption capacity of the sorbent for Cr(III) was 9.34 mg/g. The relative standard deviation was 3.2% (n = 7, c = 10 ng/mL). The method was applied successfully to the determination of Cr(III) and Cr(VI) in natural water samples.     

Determination of Tetracycline by Microdroplet Hydrodynamic Adsorptive Voltammetry Using a Multiwalled Carbon Nanotube Paste Rotating Disk Electrode

A novel and simple method is proposed for the determination of tetracycline by adsorptive voltammetry in a droplet using a carbon nanotube paste rotating disk electrode (CNTP-RDE). An enhanced electrochemical oxidation response of tetracycline was observed in pH 8.2 supporting electrolyte by the addition of a long-chain cationic surfactant, such as benzyldimethyltetradecylammonium chloride (zephiramine). Under the optimized experimental conditions, the calibration curve was linear across a tetracycline concentration range from 1.0?×?10^?7 to 2.0?×?10^?6 M. The limit of detection and sensitivity were 4.0?×?10^?8 M and 0.9358?A M^?1, respectively. This method was successfully employed for the determination of tetracycline in milk samples.     

Separation of Ethyl Anthranilate Azopigments from Germ-Free Rat Feces by Reversedphase High-perform Ance Liquid Chromatography

Abstract

A simple method was developed for the separation of ethyl anthranilate azopigments derived from conjugated bilirubins prepared from germfree (GF) rat feces. The Δ and α₀ azopigments were separated and these two azopigments were also separated into their endo-vinyl- and exo-vinyl isomers, respectively. The reverse-phase, high-performance liquid chromatographic (HPLC) separation was achieved by using a μBondapak C₁₈ column and a mixture of acetonitrile, distilled water and sodium acetate as the mobile phase.     

UPLC-MS/MS method for the determination of acrylic acid in tap water

Abstract

A simple and rapid method employing ultra-high performance liquid chromatography tandem mass spectrometry has been developed for the direct determination of acrylic acid in tap water for the first time. The method worked on a ultra-high-performance liquid chromatography system and utilized the direct injection of 10?μL volumes. Aqueous samples were filtered with 0.22?μm membrane after diluting with the acetonitrile without any further pretreatment. The separation was accomplished by using a HILIC column with a gradient elution program. Acetonitrile and ammonium acetate solution (pH = 7) were applied in the method as the mobile phase. Acrylic acid- d₃ was used as the internal standard in the quantification process. The method provided good recovery from 102.8% to 104.4%, good precision with intraday relative standard deviations in a range of 2.3% and 5.1%. The limit of quantification for the method was 45?μg/L. The possible structures of qualitative ion and quantitative ion of acrylic acid were proposed in this work with the help of the product ion spectra of acrylic acid and its corresponding isotopic standards. This study provided a reliable and quantitative method that could be used for daily monitoring of water quality.     

Improved Liquid Chromatographic Method for Acyclovir Determination in Plasma

Abstract

A simple and reproducible method for determining acyclovir (ACV) in plasma is presented. The method involved the use of acetaminophen as internal standard. A single extraction step was performed using trichloroacetic acid for protein separation. After pH adjustment, samples from the supernatent layer were directly injected into a high pressure liquid chromatograph. Components separation was perfected through manipulation of solvent combinations and pH. The acyclovir and the internal standard retention times were 8.5 and 11 min. respectively. High correlation was obtained between AUC and the drug concentration (r>0.99). Statistical analysis showed that the method is highly reproducible for ACV determination in aqueous solutions or in plasma. The mean drug recovery was better than 88%. The sensitivity obtained should enable the use of the method in future bioavailability and/or pharmacokinetic studies.     

Separation and Determination of D-Gluconic Acid Produced During Fermentation by Capillary Zone Electrophoresis

Abstract

A novel method was developed for separation and determination of D-gluconic acid produced during fermentation by capillary zone electrophoresis (CZE) with direct UV detection at 214 nm, using selected carrier electrolyte composed of 6 mM potassium biphthalate, 50 mM disodium hydrogen phosphate and 15% (v/v) acetonitrile. The effects of concentration of phthalate, phosphate and organic modifier (acetonitrile), as well as temperature for the separation were investigated. The method is simple, inexpensive and will make it very useful in the gluconic acid industry.     

Biamperometric Determination of Tetracycline in Pharmaceuticals

Abstract

A fast, reliable, and low cost biamperometric flow‐injection method, with an error of 1.3% and an analytical throughput of 55 samples h^?1, for determination of tetracycline hydrochloride in pharmaceuticals capsules is proposed. The analytical curve was linear (r=0.998) in the range 10 to 50 mg l^?1 using Fe(CN)₆ ^3? and NaOH solutions as reagent and carrier stream/supporting electrolyte, respectively. A relative standard deviation of 1.6% (10 sequential injections of 30.0 mg l^?1) was verified with detection and quantification limits of 0.6 and 3.4 mg l^?1, respectively.     

The Separation of Conjugated and Unconjugated Bilirubin in Bile by High-Performance Liquid Chromatography

Abstract

A fast and simple method was developed for the separation of unconjugated bilirubin and its mono- and di-glucuronide conjugates from bile by high-performance liquid chromatography (HPLC). Unconjugated bilirubin was separated on a reversed-phase column using acetonitrile-water (70:30 v/v) as the mobile phase, while the conjugates were separated on a μ-Bondapak-carbohydrate column employing acetonitrile-water (90:10 v/v) as the eluent. The application of this method was demonstrated by the analysis of the bile pigments in rat bile.     

水热合成具有分级结构的钨酸铋纳米花及其光催化降解四环素性能

采用一种简单的无模板水热合成法制备了具有分级结构的钨酸铋纳米花,并将钨酸铋纳米花材料应用于可见光催化去除水中的四环素类抗生素。通过X射线粉末衍射、扫描电镜、透射电镜、紫外固体漫反射、比表面分析等一系列物理表征对光催化剂和催化反应体系进行了表征。研究结果表明钨酸铋纳米光催化剂对四环素类抗生素（四环素和土霉素）均具有良好的降解能力。此外,催化剂对碱性溶液中四环素的降解效率普遍较高,且该催化剂表现出良好的循环稳定性。