High-performance Liquid Chromatogra Research Articles

역상 크로마토그래피에서 모멘트 방법과 van Deemter 식을 이용한 고리형 아데노신 일인산의 분리특성 연구

The moment analysis of cyclic adenosine monophosphate (cAMP) was performed using chromatograms that were obtained with the pulse input method from an octadecyl silica (ODS) high-performance liquid chromatogra- phy (HPLC) column. The general rate (GR) model was employed to calculate the first absolute moment and the second central moment. Three important coefficients for moment analysis, which are molecular diffusivity (Dm), external mass transfer coefficient (kf), and intra-particle diffusivity (De), were estimated by the Wilke-Chang equation, Wilson-Gean- koplis equation, and comparing van Deemter equation to theoretical plate number equation, respectively. Experiments were conducted by various conditions of flow rates, methanol volume ratio of the mobile phase, and solute concentra- tion. After the moment analysis, results were organized by van Deemter plots. Also van Deemter coefficients were com- pared each other to effect Hax, Hf, and Hd on height equivalent to a theoretical plate (HETP, Htotal). The value of intra- particle diffusion (Hd) was the primary factor which makes for HETP whereas external mass transfer (Hf) was disre- gardable factor.

Quantitative and Comparative Contents of Nitrate and Nitrite in Beta vulgaris L. by Reversed-Phase High-Performance Liquid Chromatography-Fluorescence

The consumption of beetroot, a food rich in nitrate, has been recommended to enhance blood perfusion, restore endothelial function, and improve exercise performance. These properties may be explained by the possible effect of nitrate present in beetroot in stimulating the endogenous syn- thesis of nitric oxide, a potent vasodilator. However, there is limited evidence giving detailed information about how ni- trate contents from beetroot used in studies have been ana- lyzed. The purpose of this study was to evaluate nitrate and nitrite contentsofbeetrootfromdifferentregions ofBrazil and from the USA. Nitrate and nitrite contents were quantified by using a reversed-phase high-performance liquid chromatogra- phy system with fluorescence detection. Beetroots from the USA showed the highest nitrate (31.2±0.010 mmol.L �1 )a nd nitrite (0.45±0.005 mmol.L �1 ) contents when compared to beetroots from Brazil. Rio de Janeiro was the region that showed the highest nitrate content (17.1±0.020 mmol.L �1 ), while Rio Grande do Norte presented the highest nitrite con- tent (0.13±0.010 mmol.L �1 ). The reversed-phase high-perfor- mance liquid chromatography-fluorescence method may be applied for the quantification of nitrate and nitrite contents in beetroot samples. The results of the present study demonstrate that beetroots may vary in their nitrate and nitrite contents.

Water Uptake and Urea Release of Hydrogels Based on Acrylamide, Methyl Methacrylate and N,N’–Methylene–bis–Acrylamide

Water swelling kinetics, equilibrium water content, urea release kinetics, and freezable and non–freezable water of hydrogels based on acrylamide (AM), methyl methacrylate (MMA) and N,N’–methylene–bis– acrylamide (NMBA) were studied. A series of copolymeric gels of AM, MMA and NMBA as a crosslinker agent were prepared by free radical solution copolymerization using a mixture of ethanol and water as a solvent and benzoyl peroxide (BPO) as initiator. Equilibrium water content (Wω) was strongly influenced by copolymer composition. For hydrogels richer in AM, EWC increased as crosslinking decreased. Instead, for high content methacrylate hydrogels, the hydrophilicity of NMBA decreased Wω. Swelling process in distilled water was studied by dynamic swelling measurements (gravimetric method ). It was found that synthesized hydrogels fits second–order swelling. Urea release studies were carried out in distilled water and the urea concentration was determined by High Performance Liquid Chroma togra phy (HPLC). The hydrogels del ivered urea very ra pidl y, for all the studied compositions most of the urea was released in less than 200 minutes. Differential Scanning Calorimetry (DCS) was employed to determine the relative proportions of non–freezing and freezing water. DSC traces shown multiple endotherms that were related with different states of association between water and the polymeric matrix.

Recent Advances in DNA Phosphorothioation Modification Studies

DNA phosphorothioate (PT) modification is a sulfur modification on DNA backbone, in which a non-bridging P—O bond is changed into a non-bridging P-S bond, being the first physiological modification described on the DNA back- bone. It is found that the DNA with backbone phosphoration has DNA degradation (Dnd) phenotype upon running electro- phoresis in Tris buffer. Moreover, this DNA phosphorothioation belongs to a kind of post-replication modification, where sulfur is incorporated stereo-specifically (i.e., it's a chiral Rp-type modification, not Sp-type configuration) into DNA back- bone at specific sequences. For example, a high frequency of GA was found to be phosphorothioated in Bermanella marisru- bri RED65 and Hahella chejuensis KCTC2396, determined by using high pressure or high performance liquid chromatogra- phy (HPLC) and mass methods. DNA phosphorothioation is widespread and quantized in bacterial genomes. It was reported that this DNA PT modification is controlled by the five proteins (DndA-E) encoded by dna degradation (dnd) genes cluster (dndA-E) in a sequence found in bacteria and archaea, but the mechanism about how these five proteins function during the pathway of DNA backbone PT modification remains elusive. Among these five genes, four of them, dndA and dndC-E, are essential for the PT modification, while inactivation of dndB resulted in increased phosphorothioation and altered sequence preference. In this paper, we reviewed the discovery history, the features of DNA phosphorothioation modification, and the recent research progresses on the structures and functions of the five proteins involved in DNA backbone phosphorothioation. We also discussed the antioxidant activities of phosphorothioated DNA in biological systems. Finally, for easily understand- ing the research direction in DNA phosphorothioation, we summarized several questions in the future studies on DNA PT modification, which includes: (1) How sulfur is incorporated into DNA backbone in biological system? (2) How the DNA phosphorothioation is affected by the proteins DndA, DndB, DndC, DndD and DndE? (3) How to get soluble DndB, DndC and DndD in a large quantity? (4) How DndA functions as a cysteine sulfur transferase, because the active site is in a rigid β- sheet conformation? Keywords DNA; phosphorothioate; DndA-E; Dnd phenotype; review

Comparative separation of chiral compounds by supercritical fluid chromatography and high performance liquid chromatography

Supercritical fluid chromatographic (SFC) technique has been widely applied in the analysis, determinations and chromatographic preparations of chiral compounds in past decades due to some advantages such as fast speed, high efficiency and low consumption of organic sol⁃ vents. Herein, 24 kinds of chiral compounds (H1-H24) have been resolved on four polysaccha⁃ ride⁃coated chiral stationary phases (CSPs) by SFC and high performance liquid chromatogra⁃ phy (HPLC), separately. Taking into account their retention times and selection factors of these compounds, SFC separation showed a better efficiency than HPLC for most of the com⁃ pounds, except for some axis⁃chiral compounds. Some complementarity between SFC and HPLC separations was observed. For H15-H17, their retentions in SFC separations showed a strengthening trend with increasing carbon numbers of side alkyl chain, whereas a reverse tend⁃ ency in HPLC separation was displayed. Most interestingly, an elution order reversal of metcon⁃ azole enantiomers was found in this work. In brief, these results would provide some valuable references for the development of SFC separation methods in the future.

Determination of related substances concentration of compound diclofenac aodium and chlorphenamine maleate tablets

Objective To establish a high performance liquid chromatogra (HPLC) method for determining the related substances concentration ofcompound diclofenac sodium and chlorphenamine maleate tablets.Methods Diclofenac sodium and chlorphenamine maleate can be separated on HyperClone 5 μ BDS C18(4.60 mm x 150 mm )column with a mixture of (CH3)(CH2)6SO3Na 15.2mg,(C2H5)3N 0.8 ml,and distilled water 800 ml,pH adjusted to 3.3 ± 0.1 with CH3COOH,then add distilled water to 1000 ml)-CH3OH-CH3CN (25∶ 30∶ 18) as mobile phase and detected at 262 nm.Injection volume:20 μ 1.Flow rate:1.0 ml/min.Results Diclofenac sodium and chlorphenamine maleate were separated from reference substances in base-line.The dection limits were 1.18 μ g/ml.Conclusion The method has strong specificity,and is simple,accurate and reproducible.It is adapted to determine the felsted substances concentration of compound diclofenac sodium and chlorphenamine maleate tablets. Key words: Compound diclofenac sodium and chlorphenamine maleate tablets; HPLC; Related substances concentration

An approach to imprint irganox 1076: Potential application to the specific migration test in olive oil

Irganox 1076 is a hindered phenolic antioxi- dant commonly added to polyolefins, whose migration from the plastic packaging into the food is regulated by European legislation. The work herein reports on an initial approach to obtain a molecularly imprinted polymer (MIP) for Irganox 1076, a previously nonimprinted target. In a subsequent step, the application of the molecularly imprinted solid-phase extraction (MISPE) to the fatty sim- ulant olive oil is tested to get its determination free of interferences using high-performance liquid chromatogra- phy with PDA detector. The influence of five variables, namely porogen, functional monomer, crosslinker, initia- tor, and initiation method was investigated through the synthesis of miniMIPs. The best results were obtained using methacrylic acid and ethylene glycol dimethacrylate in tetrahydrofuran under UV radiation with 2,2 0 -azobis-(2- methylpropionitrile). The application of MISPE to olive oil showed the potential of the imprinted polymer to clean up complex matrices. V C 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 2866-2874, 2011

Pharmacokinetic Evaluation of Metolazone Tablets using healthy Human Volunteers

A sensitive and reproducible high performance liqui d chromatography (HPLC) method has been developed and validated for the quantification of metolazone in h uman plasma, after solid phase extraction (SPE). A Good reso- lution was achieved on a reverse-phase LichroCART Purospher ® C 18 column using the mobile phase acetoni- trile–0.5% triethylamine (35:65) in isocratic eluti on with a total run time of 15 min. The analyte, metolazone , was detected by using high performance liquid chromatog ra- phy with the support of photo diode array detector. Limit of detection and Lower limit of quantification was found to be 1 and 2.5 ng/mL. The present method was succe ss- fully applied in the pharmacokinetic study of metol azone in human plasma.

Modulatory effects of amino acids on neuromuscular transmission on the crayfish fast flexor muscle

The modulatory effects of amino acids on neuromuscular transmission from an identified giant motor neuron (MoG) and abdominal fast flexor muscles of the crayfish were exam- ined using electrophysiological and pharmacological techniques. The distribution of amino acids in the cell body and axon of a single MoG was revealed using high-performance liquid chromatogra- phy with electrochemical detection. Eight different amino acids—aspartate, glutamate, glutamine, arginine, glycine, taurine, alanaine and γ-aminobutyric acid—were simultaneously detected in ei- ther the cell body or the axon of MoG. Aspartate, glutamate, alanine and arginine were present at relatively high concentration. Local pressure ejection of glutamate caused a depolarization of the abdominal fast flexor muscle fibers. On the other hand, aspartate, alanine and arginine had no clear effects on the same muscle fibers. Aspartate and arginine, however, had modulatory effects on neuromuscular transmission. Alanine had no significant effect on the neuromuscular transmission. Aspartate at a concentration of 200 μM decreased the amplitude of EJPs in the fast flexor muscle mediated by stimulation of both the MoG and non-giant fast flexor motor neurons. Arginine at a concentration of 200 μM reduced the EJP amplitude of the muscle fibers in response to MoG stimulation but enhanced the EJP amplitude of the same muscle fibers by stimulation of non-giant fast flexor motor neurons. Although rather high concentration (1 mM) were required, aspartate increased and arginine de- creased the depolarization of the muscle fibers induced by local ejection of glutamate. The oppo- site effect of arginine on the fast flexor muscles in response to the stimulation of different motor neurons suggested its modulatory role in the different effects of these motor neurons (depression and facilitation) in the fast flexor muscles. J. Exp. Zool. 283:531n540, 1999. © 1999 Wiley-Liss, Inc.

Method for the Determination of Veratridine and Cevadine, Major Components of the Natural Insecticide Sabadilla, in Lettuce and Cucumbers

Sabadilla, an insecticide widely used by organic farmers, can be separated into five of its components (veratridine, cevadine, cevine, cevacine, and sabadine) by high-performance liquid chromatogra...

The improvement of a multiwave high performance liquid chromatogra phy detection system for the purpose of diagnosis

High performance liquid chromatography(HPLC)using a multiwave detector possesses the advantage of being able to measure both the absorption spectra and the retention time. But conventional multiwave detector with diode arrays has lower sensitivity than commercial single wave UV detector with photomultiplier tubes and shows a marked decrease of sensitivity in the UV region below200n m. With our multiwave HPLC detection system, mechanical scanning with a rotary slit is conducted with a photomultiplier that has full sensitivity in the wavelength renge of160-650nm. And absorption due to oxygen below the200nm wavelength region has been inhibited by filling the optical system with nitrogen . This has resulted in an improvement in this system's detection sensitivity enabling it to measure in the UV region below200nm. Using this system, we tried out multiwave HPLC analysis for a number of clinical chemically important saccarides and amino acids without using some coloring reagents. As a result of this it was found possible to detect absorption peaks of each component below a wavelength of200nm, and the possibility of conducting qualitative analysis from the absorption spectra of the components was also demonstrated.