• Journal of Korean Society on Water Environment
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• v.32 no.6
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• pp.670-699
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• 2016

In this study, 16 antibiotics were selected from among the top 30 veterinary antibiotics sold in South Korea in 2014, as well as from among the pharmaceuticals targeted by EPA method 1694, in order to review analytical methods for the detection of trace levels of antibiotics in environmental samples: surface water, soils, animal origin foods, and manures. LC-MS/MS was heavily used. In the chromatography for the detection of the selected antibiotics, the $C_{18}$ column was mostly used at the temperature of $30{\sim}40^{\circ}C$. Water and methanol/acetonitrile were commonly chosen as a nonpolar and a polar mobile phase, respectively. Gradient elution was applied to separate multiclass antibiotics. Volatile additives, such as formic acid, acetic acid, and ammonium acetate were mixed with the mobile phase to improve the ionization efficiency of analytes and the sensitivity in MS detection. Electrospray ionization (ESI) was widely used in the LC-MS/MS and positive ionization was preferred to determine the selected antibiotics. A protonated $[M+H]^+$ molecule was selected as a precursor ion, and its two transitions were analyzed, one for quantitative measurement and the other for confirmation. This study reviewed linearity of the calibration curve, recovery, repeatability, method detection limits (MDLs), and method quantification limits (MQLs) for each target compound used to validate the developed analytical methods.

• Korean Journal of Medicinal Crop Science
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• v.21 no.3
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• pp.213-219
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• 2013

This study was carried out to find out the optimum method of preparation of indigo standard solution and its stability, and to investigate the indigo contents in Niram, blue dye extract, from a total of 7 indigo plants and 34 breeding lines of Persicaria tinctoria H. Gross. Proper solvent for indigo standard was dimethyl sulfoxide (DMSO), and appropriate concentration was 1 mg of indigo in 10 mL of DMSO. Absorbance value of UV/Vis Spectrophotometer at 620 nm of standard solution was changed decreasingly 12 hours after the preparation of standard solution irrespective of the storage conditions such as temperature and light. Average value of absorbance of 8-fold diluted standard solutions prepared daily during 16 days was $0.210{\pm}0.005$, indicating the powder of indigo compound was stable chemically. Calibration curve was made for quantitative analysis of indigo of 7 Niram samples, and indigo contents ranged from 0.69% to 18.76% showing relatively larger variation. Across all 34 breeding lines, the range of indigo content was from 7.9 mg to 56.4 mg per 100 g of fresh leaves, averaging 25.2 mg of indigo content and showing a 47.7% coefficient of variation.

• Analytical Science and Technology
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• v.8 no.4
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• pp.611-615
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• 1995

The design of appropriate chemically modified electrodes should allow development of new voltammetric measurement schemes with enhanced selectivity and sensitivity. Microorganism like algae has high ability to trap toxic and heavy metal ions and different affinities for metal ions. A copper(II) ion-selective carbon paste electrode was constructed by incorporating alga Anabaena into a conventional carbon paste mixture, and then the film of 10% Nafion was coated to avoid the swelling of the electrode surface. Copper ion could be deposited at the 25% algamodified electrode for 15 min without the applied potential while stirring the solution by only immersing the electrode in a buffer (pH 4.0) cot1taining copper(II). Temperature was controlled at $35^{\circ}C$. After preconcentration was carried out the electrode was transferred to a 0.1 M potassium chloride solution and was reduced at -0.6 volt at $25^{\circ}C$. The differential pulse anodic stripping voltammetry was employed. A well-defined oxidation peak could be obtained at -0.1 volt (vs SCE). In five deposition / measurement / regeneration cycles, the responses were reproducible and relative standard deviations were 3.3% for $8.0{\times}10^{-4}M$ copper(II). Calibration curve for copper was linear over the range from $2.0{\times}10^{-4}M$ to $1.0{\times}10^{-3}M$. The detection limit was $7.5{\times}10^{-5}M$. Studies of the effect of diverse ions showed that the coexisting metal ions had little or no effect for the determination of copper. But anions such as cyanide. oxalate and EDTA seriously interfered.

• Applied Biological Chemistry
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• v.18 no.1
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• pp.52-55
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• 1975

A microdetermination of Ascorbic acid (AsA) in blood by Gas-Liquid Chromatography (GLC) was studied. AsA was applied on GLC after the conversion into trimethylsilyl derivative (TMS) and the GLC was available for the only reduced form of AsA. A calibration curve is made by GLC of TMS-AsA as the internal standard of n-docosane. The minimum amount of AsA required for the determination was 0.5ml of 1 mg% pyridine solution. Prior to the conversion of AsA in serum into TMS derivative, serum was lyophilized and then it was allowed to stand at room temperature with TMS reagents for 48 hr. On injection of the supernates of TMS derivative to GLC the peak corresponding to AsA was not detected. Its reason why the concentration of AsA in serum is $0.5mg{\sim}0.8mg%$ in general, and it is less than minimum concentration of GLC. In case of L-AsA 1 mg was added to 1ml of serum, which was followed by lyophilization, silylation and GLC. The recorvery of AsA added was 98 percentage.

• YAKHAK HOEJI
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• v.55 no.1
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• pp.64-68
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• 2011

In this study, a high performance liquid chromatography-diode array detector method was established, for simultaneous determination of three compounds, berberine, palmatine and geniposide in Hwangryunhaedok-tang, To develop and validate method, $C_{18}$ column (5 ${\mu}M$, 4.6 mm${\times}$250 mm) was used with gradient mobile phase, water containing 0.1% trifluoroacetic acid (TFA) and MeOH at the column temperature of $30^{\circ}C$. UV wavelength was set at 230 and 280 nm. Validation of the chromatography method was evaluated by linearity, precision and accuracy test. Calibration curve of standard components showed good linearity ($R^2$ > 0.9999). The limits of detection (LOD) and limits of quantification (LOQ) varied from 0.05 to 0.17 ${\mu}g/ml$ and 0.15 to 0.53 ${\mu}g/ml$, respectively. The relative standard deviations (RSDs) data of intra-day and inter-day test were in less than 2.99% and 1.90%, respectively. The results of the accuracy test were in the range of 98.36 to 102.52% with RSDs values 0.32 to 1.98%. The results of validation indicated that this method was a very accurate and sensitive assay.

• Journal of the Korean Chemical Society
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• v.45 no.3
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• pp.223-229
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• 2001

A method for the determination of glucose in human whole blood by chemiluminescence method using a stopped flow injection system has been studied. The method is based on the differences in the chemiluminescence intensities of luminol due to the different amounts of hydrogen peroxide produced from the glucose oxidase catalyzed reaction. The enzyme reactor was prepared by immobilization of glucose oxidase on aminopropyl glass beads and the chemiluminescence from a flow cell was measured by means of an optical fiber bundle. In order to obtain the optimum experimental conditions, effects of pH for the chemiluminogenic solution and enzyme reactor, flow rate and temperature on the chemiluminescence intensity were investigated. The calibration curve obtained under optimum experimental conditions was linear over the range from $1.0{\times}10^{-1}$ mM to 7.0 mM and the detection limit was $6.0{\times}10^{-2}$ mM. The proposed method was applied to the determination of glucose in whole human blood sample and the results were compared with those obtained by an official method. The present method was also evaluated by the results of recovery experiments.

• Journal of the Korean Chemical Society
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• v.44 no.6
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• pp.556-562
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• 2000

The determination of chlorite ion by flow injection analysis(FIA) with iodometric UV detection were investigated. Under rather acidic condition, chlorite ion react with iodide ion to form iodine and itself is reduced to chloride ion. The chlorite ion was determined indirectly by measuring absorbance of yellow colored iodine at 370 nm. The lengths of the mixing coil and the reaction coil, the pH of the acid stream, the concentration of the iodide ion, the injection loop volume, temperature, and flowrate were optimized as parameters for selectively determining a sort of inorganic disinfection by-product, chlorite ion by using FIA-UV detection setup. Masking agents for removing oxidants or interferences from the prepared water were tested. Independent calibration curve presented linear range of 0.002-0.2 mg/L for chlorite ion with a correlation coefficient of 0.999 or better. The limit of detection(LOD) was 0.18 ${\mu}g/L$ for chlorite ion.

• The Korea Journal of Herbology
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• v.23 no.3
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• pp.27-32
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• 2008

Objectives : In this paper, we describe that $^1H-NMR$ spectroscopy may be superior to the conventional HPLC for the quantitative analysis of hesperidin from Citrus unshiu. Methods : $^1H-NMR$ spectra (400 MHz) were recorded in $DMSO-d_6$ using a Varian UNITY Inova AS 400 FT NMR spectrometer. One hundred milligram of powdered Citrus unshiu was weighed out and mixed with 1 ml of $DMSO-d_6$ with sonication for 30 min (room temperature). The extracts were filtrated through a 0.45 ${\mu}m$ PVDF filter and 0.5 ml of filtrated extract used for quantitative $^1H-NMR$ measurement (added 1 mg of dimethyl terephthalate as internal standard). The quantity of hesperidin was calculated by the ratio of the intensity of the compound to the known amount of internal standard. For HPLC analysis, the half gram of plant material was extracted with 60 ml of MeOH for 2 hours. The extracts were made 100 ml volume and analyzed by a Waters HPLC system using a YMC ODS column. The total flow rate was 1.0 ml/min with a sample volume 10 ${\mu}l$ and UV detection at 280nm. Results : The contents of hesperidin in Citrus unshiu was determined $5.33{\pm}0.06$% in the quantitative $^1H-NMR$ method and $5.15{\pm}0.12%$ in HPLC method. Using the quantitative $^1H-NMR$ the contents of hesperidin can be determined in much shorter time than the conventional HPLC measurements. Conclusions : From those results, the advantages of quantitative $^1H-NMR$ analysis are that can be analyzed to identify and quantify, and no reference compounds required for calibration curve. Besides, it allows rapid and simple quantification for hesperidin with an analysis time for only 10 min without any pre-purification steps.

• Journal of Sensor Science and Technology
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• v.2 no.1
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• pp.35-40
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• 1993

A FET(field effect transistor) type lipid sensor was fabricated uy immobilizing lipase enzyme on the gate of pH-ISFET($SiO_{2}/Si_{3}N_{4}$). A water soluble polymer, polyvinyl alcohol(PVA) was modified with 1-methyl-4-(formyl-styryl) pyridinium methosulfate(SbQ) to give a photosensitive membrane(PVA-SbQ) in which lipase was immobilized. The optimum photolithographic conditions were ; spin coating speed $5,000{\sim}6,000$ rpm. UV exposure time $20{\sim}30$ seconds, developing time in water $30{\sim}40$ seconds, and vacuum drying time 45 min. at room temperature with the suspension containing PVA-SbQ aqueous solution(SbQ 1mol%, 10 wt %) $200{\mu}L$, bovine serum albumin (BSA) 7.5 mg, and lipase 10 mg. The lipid sensor showed good linear calibration curve in the range of $10{\sim}100$ mM triacetin as a lipid sample.

• Korean Journal of Pharmacognosy
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• v.49 no.4
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• pp.328-335
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• 2018

'EGCG(epigallocatechin gallate) rich Green Tea extract(EGTE)' was prepared by a convenient chromatographical manner using water and alcohol which was regarded as the most suitable and appropriate process for food manufacturing. The EGCG content in EGTE was estimated above 97%. Analysis of polyphenol components in green tea, i.e., catechin(C), epigallocatechin(EGC), epicatechin(EC), epigallocatechin gallate(EGCG), epicatechin gallate(ECG) and caffeine was performed by HPLC. The optimized HPLC method exhibited a good linearity of calibration curve, accuracy and precision. The long-term stability evaluation of EGTE was carried out with a powdered formulation and solution formulation by estimating the color change and measuring the EGCG content by HPLC analysis for one year. The EGCG content of the powdered EGTE stored in a transparent bottle at room temperature was retained over 97% at the end of the experimental period. The EGCG content of 0.1% water solution of EGTE stored in a transparent bottle at RT were observed to decrease below 30%, whereas that stored at $2^{\circ}C$ retained over 70%, respectively. These results suggested that a powdered formulation could be recommended for the commercialized nutraceutical product of EGTE rather than a solution formulation.