• Biomolecules & Therapeutics
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• v.13 no.2
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• pp.90-94
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• 2005

Prazosin hydrochloride is an antihypertensive drug with selective ${\alpha}_1$-adrenoreceptor blocking effects. A simple high performance liquid chromatographic method has been developed and validated for the quantitative determination of prazosin in human plasma. A reversed-phase C18 column was used for the separation of prazosin and terazosin (internal standard) with a mobile phase composed of water, acetonitrile and triethylamine(75:25:0.1, V/V;pH5.0) at a flow rate of 1.5 ml/min. the fluorescence detector was set at excitation and emissionwavelengths of 250 and 370 nm, respectively. Intra-and inter-day precision and accuracy were acceptable for all quality control samples including the lower limit of quantification of 0.5 ng/ml. Good recovery (>80%) was seen in plasma. Prazosin was stable in human plasma under various storage conditions. This method was used successfully for a pharmacokinetic study in plasma after oral administration of a single 2-mg dose as prazosin base to 16 healthy volunteers. The maximum plasma concentration of prazosin was 23.1 ${\pm}$ 16.5 ng/ml at 2.1 h, and the mean area under the curve and elimination half-life were calculated to be 108.4 ${\pm}$ 74.2 ng ${\cdot}$hr/ml and 2.5 ${\pm}$ 0.6 h, respectively.

• International Journal of Precision Engineering and Manufacturing
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• v.2 no.3
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• pp.41-46
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• 2001

This paper discusses the feasibility of improving micro-machining accuracy by using two-dimensional(2-D) vibration cutting. Vibration cutting is generated by two piezo actuators arranged orthogonally : one is actuated by a sine curve voltage input, and the other is actuated by a phase-shifted sine curve voltage. A tool attached to the vibrator oscillates in a 2-D elliptical motion, depending on the frequencies, amplitudes, and the phase shifts of two input signals and the workpiece feedrate. Along the elliptical tool locus, cutting is done in the lower part, and non-cutting is done in the upper part. By this way a unique feature of 2-D vibration cutting, that is, air lubrication between a tool and chips, is caused. Another unique feature of 2-D vibration cutting was experimentally verified, that is, some negative thrust force occurs as the direction of chip movement on a tool rake face is reversed. Those features not only help chips flow smoothly and continuously but also reduce cutting force, which results in a higher quality machined surface. Through tool path simulations and experiments under several micro-machining conditions, the 2-D vibration cutting, compared to conventional cutting, was found to result in a great decrease in the cutting force, a much smoother surface, and much less burr.

• Korean Journal of Veterinary Research
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• v.48 no.1
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• pp.9-16
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• 2008

A method for the quantification of eugenol in the medicinal herb Clove was developed and validated. For preparation of sample solutions clove was dried at $60^{\circ}C$ for 2h and ground by mixer and extracted with 95% ethanol for shaking extraction. The elutes were analyzed by HPLC system included a reversed phase column, a isocratic mobile phase of 60% methanol and PDA detector set at 280 nm. Calibration graphs were linear with very good correlation coefficients ($r^2>0.9999$) from $0.0125~1{\mu}g/ml$. The limit of detection per sample injection ($20{\mu}l$) was $0.81ng/{\mu}l$ and limit of quantification was $2.47ng/{\mu}l$. The method showed good intra-day precision (%RSD 0.08 ~ 0.27%) and inter-day precision (%RSD 0.32 ~ 1.19%).

• Korean Journal of Medicinal Crop Science
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• v.14 no.5
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• pp.289-292
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• 2006

High performance liquid chromatography (HPLC) was used for the determination of lignans, eleutherosides B and E, in Acanthopanax sessiliflorus fruits and their fermented wine. The lignans were quantified by a reversed-phase system using a gradient of $H_2O$ and acetonitrile as a mobile phase within 20 min. The analysis was successfully carried out within 20 min. The contents of eleutherosides Band E as main active principles of Acanthopanax species were measured in A. sessiliflorus fruits (1.15 and $8.49\;{\mu}g/mg$, respectively), their fermented wine (0.45 and $1.33\;{\mu}g/mg$, respectively) and wine residues (no detection).

• Journal of Microbiology and Biotechnology
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• v.15 no.5
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• pp.946-951
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• 2005

Biodegradation of the endocrine-disrupting chemical di-n-butyl phthalate (DBP) was investigated using a bacterium, Pseudomonas fluorescens B-1, isolated from mangrove sediment. The effects of temperature, pH, salinity, and oxygen availability on DBP degradation were studied. Degradation of DBP was monitored by solid-phase extraction using reversed-phase HPLC and UV detection. The major metabolites of DBP degradation were identified as mono-n-butyl phthalate and phthalic acid by gas chromatography-mass spectrometry (GC-MS) and a pathway of degradation was proposed. Degradation by P. fluorescens B-1 conformed to first-order kinetics. Degradation of DBP was also tested in seawater by inoculating P. fluorescens B-1, and complete degradation of an initial concentration of $100{\mu}g/l$ was achieved in 144 h. These results suggest that DBP is readily degraded by bacteria in natural environments.

• Analytical Science and Technology
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• v.13 no.3
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• pp.282-290
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• 2000

In this study, polymer additives were extracted and separated by Soxhlet extraction method and the dissolution-precipitation method from a polycarbonate (optical grade) which completely absorbed UV light below 390 nm. Analytical techniques such as UV-Vis spectroscopy, FT-IR, and HPLC were applied to analyze additives in polycarbonate. Separated materials from the polycarbonate may be a complex mixture containing additives such as UV stabilizer, antioxidants (primary and secondary), monomers, and oligomers. Several compounds such as bisphenol A, Irganox 1010, and Cyasorb UV-5411 were identified by chromatograms and UV spectra obtained from RP HPLC analysis using Bondapak $C_{18}$ column, methanol mobile phase, and a photodiode array (PDA) detector. Also, the content of UV-5411 in the polycarbonate was about 0.12 wt% by a quantitative analysis through UV spectroscopy.

• Journal of the Korean Applied Science and Technology
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• v.30 no.4
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• pp.664-671
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• 2013

Determination of xanthan gum as watersoluble-polymer in commercial cosmetic samples was carried out by High Perfomance Liquid Chromatography(HPLC). An $C_{18}$ reversed-phase column and the selected ELSD detector was applied. The 25mM ammonium acetate/acetonitrile was used for the mobile phase of gradient conditions. The analysis results of HPLC showed good linearity with correlation coefficient of $r^2=0.9993$ in the rage of $50.3{\sim}604.1{\mu}g/ml$ and detection limit of $12.0{\mu}g/ml$.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.4
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• pp.753-764
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• 1992

The steam generator water level is difficult to control at low power due to its reversed responses to the feedwater flow, which are well known as the shrink and swell phenomena. With regard to this problem a new control scheme has been studied by which the level transients could be kept within permissible ranges at low power. The relations between the various input conditions to steam generator and the level transients have been examined to be expressed in the form of process transfer functions. Analog filters have been incorporated to be expressed in the process with proper control constants. This control scheme allows the prediction of level variation together with the corresponding feedwater rate and results in mider transients with good stabilites.

• Journal of the Korean Chemical Society
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• v.34 no.4
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• pp.345-351
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• 1990

Optical isomers of DABS-amino acids have been separated in a reversed phae high performance liquid chromatography by adding Cu (Ⅱ)-L-Proline chelate to the mobile phase. The retention behaviors for the DABS-amino acids are discussed in terms of pH of the mobile phase and the concentrations of acetonitrile, Cu (Ⅱ) complex, and buffer. The selectivity of the optical isomers of DABS-amino acids increases with the pH of the mobile, and the concentration of the chelate, but decreases with concentration of the oganic modifier. The concentration of buffer does not affect the optical separation selectivity. A separation mechanism is illustrated by cis and trans formation based on the steric effect of the ligand exchange reaction between DABS-amino acids and the copper chelate.

• YAKHAK HOEJI
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• v.30 no.6
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• pp.311-316
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• 1986

A new UV labeling reagent was developed and used in HPLC for the determination of prostaglandin $E_2$ which have weak UV light-absorbing property. This reagent, 2-bromoacetyltriphenylene, was synthesized by the bromination of 2-acetyltriphenylene which was obtained from triphenylene by Friedel-Crafts reaction. The wave length maximum (${\lambda}_{max}^{CH_3CN}$ of this reagent was 268nm. Prostaglandin E$_2$ was extracted from prostaglandin E$_2$-$\beta$-cyclodextrin using a Sep-pak $C_{18}$ cartridge. The prostaglandin E$_2$ was labeled with 2-bromoacetyl-triphenylene in aectonitrite using 18-crown-6-ether as catalyst. Derivatized prostaglandins were separated on a reversed-phase column (Radial-pak) $\mu$-Bondapak $C_{18}$ using acetonitrile: water=60:40 as mobile phase. The effluent was monitored by UV detector at 254nm filter kit. Linearity of calibration curve was obtained between 30ng and 140ng, and the lower limit of detection was 5ng.