• Journal of Food Hygiene and Safety
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• v.18 no.2
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• pp.43-50
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• 2003

A liquid chromatographic method, using matrix solid-phase dispersion (MSPD) is developed for the extraction of residual furazolidone in chicken eggs. Blank or fortified egg samples (0.5 g) were blended with Octadecylsilyl (Bulk $C_{18}$, 40${\mu}{\textrm}{m}$, 18%. load, endcapped. 2 g) derivatized silica. After homogenization, $C_{18}$/egg and Na$_2$S $O_4$matrix were transferred to a column made of 10 ml glass syringe and filter paper and compressed 4.0∼4.5 ml volume. The column was washed with 8 ml of hexane and dried under $N_2$ gas. Furazolidone was eluted with acetonitrile (8 ml) under gravity. The eluate containing furazolidone was free from interfering compounds when analyzed by HPLC with UV detection (365 nm, photodiode array). Calibration curves were linear (r = 0.99985) and inter- (1.47%) and intra-assay (5.29%) variabilities for the concentration range examined (7.8∼497 ng/g of eggs, 20 ${mu}ell$ injection volume) were indicative of an acceptable methodology for the analysis of furazolidone. Average recovery of furazolidone added to egg was 96.2%. The limit of detection for the proposed method was 1 ng/g for furazolidone. The method using MSPD is proposed as an alternative assay to the classical method which involves the use of large volumes of a harmful solvent and requires a long tedious separation and clean-up processes prior to its determination.

• Analytical Science and Technology
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• v.21 no.4
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• pp.284-295
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• 2008

For plastics samples, a method using combustion ion chromatography was selected as a method for rapid low-cost analysis to test whether hazardous substances are contained or not. Using combustion ion chromatography, a verification test for F, Cl and Br compounds generated a linear calibration curve with a correlation coefficient of $r^2$ = 0.999~1.000 in the calibration range from 0.5 to 4.0 mg/kg. The detection limits were found to be 0.005~0.024 mg/kg and quantitative limits were found to be 0.014~0.073 mg/kg. The recoveries of combustion ion chromatography using certified reference material (CRM) were found to be 95.5~104.9%. Based on these results, a proficiency test was conducted together with several laboratories in and out of the country, to make comparative analysis of the results from each laboratory. As a result, the data supported the use of combustion ion chromatography as an effective analysis method to deal with regulations for halogen-free electronic products and for other hazardous substances in the electronic products.

• Journal of The Korean Astronomical Society
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• v.42 no.6
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• pp.155-159
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• 2009

In order to determine color excess in the $uvby\beta$ color system for high amplitude $\delta$ Scuti stars, reddening free $[m_1]$, $[c_1]$, and $\beta$ indices data were obtained from the existing literature for 21 stars. Then, the three intrinsic relations of $(b-y)_0$ - $[m_1]$, $(b-y)_0$ - $[c_1]$, and $(b-y)_0$ - $\beta$ were investigated. Among these, it was shown that the $(b-y)_0$-$[c_1]$ relation is the most useful. By establishing intrinsic $(b-y)_0$-$[c_1]$ relations for six reddening calibration stars, color excesses of other stars were determined.

• Korean Journal of Agricultural and Forest Meteorology
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• v.7 no.1
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• pp.91-97
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• 2005

Class A evaporation pan has been used throughout the world to measure free water evaporation mainly by manual observation once a day. In this study, a new automatic water level measurement method is used for understanding of free water evaporation and numerical analysis. This new technique measures the weight of buoyancy bar in water, and does not need calibration because it is not affected by water density change with water temperature. Field observations of evaporation were made near Haenam Meteorological Station over paddy field located in southwestern Korea from 20 April to 30 May 2004 and the data from ten clear days (16 - 25 May) were used for this analysis. The observed total evaporation was about 50.7mm during this period whereas the estimated from an empirical equation was 50.4mm. As expected, the pan evaporation is well correlated with wind speed and the vapor pressure deficit between the water surface and the air.

• Structural Engineering and Mechanics
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• v.28 no.5
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• pp.525-548
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• 2008

This article deals the theory for solving an inverse problem of plate structures using the frequency-domain information instead of classical time-domain delays or free vibration eigenmodes or eigenvalues. A reduced set of output parameters characterizing the defect is used as a regularization technique to drastically overcome noise problems that appear in imaging techniques. A deconvolution scheme from an undamaged specimen overrides uncertainties about the input signal and other coherent noises. This approach provides the advantage that it is not necessary to visually identify the portion of the signal that contains the information about the defect. The theoretical model for Quantitative nondestructive evaluation, the relationship between the real and ideal models, the finite element method (FEM) for the forward problem, and inverse procedure for detecting the defects are developed. The theoretical formulation is experimentally verified using dynamic responses of a steel plate under impact loading at several points. The signal synthesized by FEM, the residual, and its components are analyzed for different choices of time window. The noise effects are taken into account in the inversion strategy by designing a filter for the cost functional to be minimized. The technique is focused toward a exible and rapid inspection of large areas, by recovering the position of the defect by means of a single accelerometer, overriding experimental calibration, and using a reduced number of impact events.

• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.197-203
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• 2014

A rapid, accurate and precise method for the determination of 22 amino acids in Isatidis Radix by Hydrophilic Interaction Ultra-High-Performance Liquid Chromatography Coupled with Triple-Quadrupole Mass Spectrometry (HILIC-UPLC-MS/MS) was established. Chromatographic separation was carried out on a Acquity UPLC BEH Amide column ($2.1mm{\times}100mm$, $1.7{\mu}m$) with gradient elution of acetonitrile (containing 0.05% formic acid and 2 mM ammonium formate) and water (containing 0.15% formic acid and 10 mM ammonium formate) at a flow rate of 0.4 mL/min; Waters Xevo$^{TM}$ TQ worked in multiple reaction monitoring mode. All components were separated in 17 min. All calibration curves were linear ($R^2$ > 0.991) over the tested ranges. The limits of detection (LOD) and limits of quantitation (LOQ) for these compounds were 0.21-79.55 and 0.72-294.23 ng/mL, respectively. The average recoveries were in the range of 93.75-104.16% with RSD value less than 6.56%. Therefore, this method could be an alternative assay for the determination of 22 amino acids in Isatidis Radix due to its rapidness, sensitivity, less sample and solvent consumption.

• International Journal of CAD/CAM
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• v.9 no.1
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• pp.37-46
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• 2010

Existing methods for the registration of blurred images are efficient for the artificially blurred images or a planar registration, but not suitable for the naturally blurred images existing in the real image mosaic process. In this paper, we attempt to resolve this problem and propose a method for a distortion-free stitching of naturally blurred images for image mosaic. It adopts a multi-resolution and robust feature based inter-layer mosaic together. In each layer, Harris corner detector is chosen to effectively detect features and RANSAC is used to find reliable matches for further calibration as well as an initial homography as the initial motion of next layer. Simplex and subspace trust region methods are used consequently to estimate the stable focal length and rotation matrix through the transformation property of feature matches. In order to stitch multiple images together, an iterative registration strategy is also adopted to estimate the focal length of each image. Experimental results demonstrate the performance of the proposed method.

• Applied Chemistry
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• v.15 no.2
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• pp.113-116
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• 2011

A sensitive and selective determination method of Fe(II) ion by luminol-H₂O₂ system using a chelating reagent has been presented. A metal ion-chelating ligand complex such as Fe(II)-diethylenetriamine pentaacetic acid (DTPA) produced higher chemiluminescence (CL) intensity as well as longer lifetime in luminol-H₂O₂ system than metal exist as free ions. Furthermore, the catalytic activity of Cu(II) and Pb (II) complexes with chelating reagents in luminol-H₂O₂ system was lost since chelating reagents act as a masking agent although free Cu(II) and Pb(II) ions have high catalytic activity. On the optimized conditions, the calibration curve of Fe(II) ion was linear over the range from 1.0×10^-7 to 2.0×10^-5 M with correlation coefficient of 0.996. The detection limit was calculated to be 4.0×10^-8 M.

• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.3055-3060
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• 2012

A simple, rapid and sensitive spectrofluorometric method was developed for the determination of folic acid (FA), based on its quenching effect on the fluorescence intensity of enoxacin (ENX)-europium ($Eu^{3+}$) complex as a fluorescent probe. Fluorometric interaction between ENX-$Eu^{3+}$ complex and FA was studied using UV-visible and fluorescence spectroscopy. The quenched fluorescence intensity at an emission wavelength of 614 nm was proportional to the concentration of FA. Optimum conditions for the determination of FA were investigated. Under optimal conditions, the reduced fluorescence intensity at 614 nm was responded linearly with the concentration of FA. The linearity was maintained in the range of $1.25{\times}10^{-9}$ to $1.50{\times}10^{-7}$ M (R = 0.9986) with the limit of detection ($3S_b/m$) (where $S_b$ is the standard deviation of blank and m is the slop of linear calibration curve) of $6.94{\times}10^{-10}$ M. The relative standard deviation (RSD) for 9 repeated measurements of $1.0{\times}10^{-9}$ M FA was 1.42%. This method was simple, cost effective, and relatively free of interference from coexisting substances. Successful determinations of FA in pharmaceutical formulation and biological samples with the developed method were demonstrated.

• Biomolecules & Therapeutics
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• v.27 no.2
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• pp.193-200
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• 2019

Ceramide metabolism is known to be an essential etiology for various diseases, such as atopic dermatitis and Gaucher disease. Glucosylceramide synthase (GCS) is a key enzyme for the synthesis of glucosylceramide (GlcCer), which is a main ceramide metabolism pathway in mammalian cells. In this article, we developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to determine GCS activity using synthetic non-natural sphingolipid C8-ceramide as a substrate. The reaction products, C8-GlcCer for GCS, could be separated on a C18 column by reverse-phase high-performance liquid chromatography (HPLC). Quantification was conducted using the multiple reaction monitoring (MRM) mode to monitor the precursor-to-product ion transitions of m/z $588.6{\rightarrow}264.4$ for C8-GlcCer at positive ionization mode. The calibration curve was established over the range of 0.625-160 ng/mL, and the correlation coefficient was larger than 0.999. This method was successfully applied to detect GCS in the human hepatocellular carcinoma cell line (HepG2 cells) and mouse peripheral blood mononuclear cells. We also evaluated the inhibition degree of a known GCS inhibitor 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) on GCS enzymatic activity and proved that this method could be successfully applied to GCS inhibitor screening of preventive and therapeutic drugs for ceramide metabolism diseases, such as atopic dermatitis and Gaucher disease.