• Bulletin of the Korean Chemical Society
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• v.33 no.7
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• pp.2224-2228
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• 2012

This study describes the ability of capillary electrochromatography (CEC) for the determination of imidacloprid and carbendazim in tomato samples. A novel liquid crystal crown ether modified hybrid silica monolithic column was synthesized, characterized and developed as separation column for the first time. Baseline separation of imidacloprid and carbendazim could be achieved using a mobile phase containing 90% (v/v) 20 mmol/L phosphate buffer (pH 7.0) and 10% (v/v) acetonitrile. The matrix matched calibration curves were linear with correlation coefficient $r^2$ > 0.9998 in the range of 0.20-10.00 mg/L. The limits of detection for imidacloprid and carbendazim were 0.061 and 0.15 mg/kg, respectively, which were below the maximum residue limits established by the European Union as well as Codex Alimentarius. Average recoveries for imidacloprid and carbendazim varied from 101.6-108.0% with relative standard deviations lower than 6.3%. This method was applied to the analysis of tomatoes collected from local markets.

• Bulletin of the Korean Chemical Society
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• v.24 no.11
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• pp.1571-1574
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• 2003

This paper describes an inductively coupled plasma emission spectrometric method for the analysis of Fe in rat plasma. Calibration curves were obtained in the range of 0.125-1.50 ${\mu}g{\cdot}mL^{-1}$. The relative standard deviation ranges from 5.93% to 6.80%, and accuracy was between 87.6 and 102.0%. Dilution with water had no influence on the performance of the method, which could then be used to quantify Fe concentration in plasma up to 0.50 ${\mu}g{\cdot}mL^{-1}$. The limit of quantification was 0.10 ${\mu}g{\cdot}mL^{-1}$. At this level, the average relative standard deviation was 6.8%. The results indicate that the method meets the accuracy and precision requirements for the pharmacokinetic studies. The Fe concentration in rat plasma was measured and the main pharmacokinetic parameters were calculated by Topfit 2.0 (GmbH. Shering AG, Godecke AG, Germany).

• Journal of the Korean Ceramic Society
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• v.20 no.1
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• pp.43-48
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• 1983

The formation of strontium titanate from several molar $SrCO_3$ and $TiO_2$ mixtures was studied in air and $CO_2$ gas Mixtures of $SrCO_3$ and $TiO_2$ were heated in air at 400-$600^{\circ}C$ DTA-TG was used to obtain thermal histories of simples heated in air and $CO_2$ gas. X-ray diffraction analysis was used to determine both the phase composition and the amounts of each phase present. The phase relationship of various compounds $SrTiO_3$, $Sr_2TiO_4$, $Sr_2Ti_3O_7$ and $Sr_4Ti_3O_{10}$ formed by the sintering in each composition was shown by the calibration curves. High temperature X-ray analysis was used to determine both the formation process and deformation process of each products. Small amount of SrTiO3 is formed first at the surface af contact SrTiO3 reacts with $SrCO_3$ to form Sr2TiO4 this is affected on the $CO_2$ pressure.

• Analytical Science and Technology
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• v.16 no.1
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• pp.59-69
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• 2003

Benzophenone (BZP) and 4-nitrotoluene (4-NT) listed as endocrine disrupting chemicals are suspected to contaminate ground water sites and soil. Analytical method for simultaneous determination of the two chemicals in soil and ground water was developed by gas chromatography-mass spectrometry. Water (100 ml) was extracted with hexane, and soil (10 g) was extracted with methanol and hexane. Recovery in water was >72% for BZP and 90-118% for 4-NT. Recovery for 4-NT and BZP in soil was 51-59% with coefficient variation of less than 19.5%. Calibration curves showed a good linearity with $r^2=0.997$. In water and soil collected at nation-wide sites, BZP was found at 5 sites among 43 water sites at the concentration of $14.87{\pm}3.83ng/100 ml$. No 4-NT was found. It is suggested that this method is appropriate to the simultaneous quantitation of 4-NT and BZP in ground water and soil samples.

• Analytical Science and Technology
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• v.18 no.6
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• pp.453-459
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• 2005

Phenol compounds in water were simultaneously analyzed by extractive derivatization. Aqueous solution was controlled to pH 13 with sodium hydroxide, and then $500{\mu}L$ of benzoyl chloride was added to the solution. The solution was shaken for 15 minutes and extracted with diethyl ether and then analyzed using GC/MS-SIM. The calibration curves of phenolic compounds in the range of 0.05 to $5.0{\mu}g/mL$ showed a good linearity having the correlation coefficient of $r^2=0.9915$ and standard deviation of ${\leq}8.5%$, respectively. The recoveries by this method ware 58.4-114.0%.

• Natural Product Sciences
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• v.22 no.2
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• pp.77-81
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• 2016

A reversed-phase high-performance liquid chromatographic method is described for the simultaneous determination of three antibacterial flavonoids, artocarpanone, artocarpin, and cycloartocarpin in ethyl acetate extracts from Artocarpus heterophyllus heartwoods. Separation was achieved using a TSK-gel ODS-80Tm column ($5{\mu}m$, $4.6{\times}150mm$) at $25^{\circ}C$ with a gradient elution system of methanol and water as follows: 0-8 min, 60:40; 8-27 min, 80:20; 27-35 min, 60:40, v/v, at a flow rate of 1 mL/min, and a quantitative UV detection at 285 nm. The method was validated by measuring the key parameters, including specificity, linearity, sensitivity, accuracy, repeatability and reproducibility. A high degree of specificity and sensitivity was achieved. The calibration curves for all three flavonoids showed good linearity with a coefficient of determinations ($R^2$) of ${\geq}0.9995$. The recoveries of the method were from 98-104%, with good reproducibility and repeatability (RSD values of less than 2%) were also achieved. Ethyl acetate was the best solvent for extraction of these three flavonoids using the heat reflux conditions for 1 h. This optimized sample preparation and HPLC method can be practically used for a routine standardization process of the extracts from the A. heterophyllus heartwoods.

• Korean Journal of Pharmacognosy
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• v.42 no.3
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• pp.240-245
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• 2011

A high-performance liquid chromatography (HPLC) method was developed for quantitative analysis of liquiritin and glycyrrhizin in Sagunja-tang (SGT, Sijunzi-tang in Chinese), a traditional Korean medicine. HPLC analysis was performed using a Gemini C18 column operating at $40^{\circ}C$, and photodiode array (PDA) detection at 254 nm and 280 nm for quantification of the two components in SGT. The mobile phase using a gradient flow consisted of two solvent systems. Solvent A was 1.0% (v/v) aqueous acetic acid and solvent B was acetonitrile with 1.0% (v/v) acetic acid. Calibration curves were acquired with $r^2$ values > 0.9998, and the relative standard deviations (RSDs, %) for intra- and inter-day precision were not exceed 4.0%. The recovery of each component was in the range of 91.85 - 108.62%, with a RSD less than 4.0%. The contents of the two components in SGT were 7.94 - 13.83 mg/g.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.7
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• pp.826-833
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• 2004

Cascade impactors are widely used to collect size classified aerosol. A major disadvantage of this instrument is the required long sampling time. Electrical low pressure impactor has been developed to overcome this disadvantage and to achieve real-time measurements on the particle size distribution. The instrument consists primarily of a corona charger, low pressure cascade impactor and multi channel electrometer. We designed and evaluated the performance of a potable 3-stage low pressure impactor using an electrical method. For the calibration of the impactor, monodispersed particles were generated using evaporation-condensation method followed by electrostatic classification using a DMA(Differential Mobility Analyzer). The collection efficiency curves of the stages can be determined by analysing the fraction of particles collected by each stage.

• Journal of Environmental Science International
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• v.14 no.4
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• pp.445-449
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• 2005

A simple and sensitive analytical method based on RP-HPLC with UV detector$(225{\cal}nm)$ and mobile phases using $0.1{\%}$ phosphoric acid and acetonitrile was developed for simultaneous determination of quinclorac, bentazone, 2,4-D, bensulfuron-methyl, dymuron, capropamide, pencycuron, ethofenprox. This method was resulted in recovery of $78{\~}96{\%}$ with RSD $3.3{\~}7.5{\%}$, LODs $0.12{\~}0.84$ and LOQs $0.34{\~}1.20{\cal}mg/L$. Calibration curves were linear with r of $0.9995{\~}0.9999$.

• Archives of Pharmacal Research
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• v.24 no.6
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• pp.601-606
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• 2001

A simple assay method of recombinant human epidermal growth factor (rhEGF) in a pharmaceutical preparation was studied and validated by capillary electrophoresis (CE) using micellar electrokinetic chromatography (MEKC) techniques. Factors affecting the migration behavior and separation performances of the peptide; type of buffers pH, butler concentration, and concentration of sodium dodecyl sulfates (SDS) were investigated to optimize the analytical performance. CE was performed using running buffers 50.0 mM borate (pH 8.5) containing 12.5 mM SDS at 20 $mutextrm{V}$ of the applied voltage. Calibration curves for the rhEGF showed good linearity (r>0.999) over the wide dynamic range from 1.25 to $100{\mu\textrm{g}}/ml$. Sample analysis was performed by using standard addition method to eliminate the matrix effects of dosage vehicle. This method is assumed to be useful for quality control (QC) of various forms of pharmaceutical products of the peptide.