• Analytical Science and Technology
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• v.21 no.1
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• pp.41-47
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• 2008

Although liquid-liquid extraction (LLE) method has been used routinely for the analysis of amphetamine-like drugs (amphetamine; AP, methamphetamine; MA, 3,4-methylenedioxyamphetamine; MDA, 3,4-methylenedioxymethamphetamine; MDMA, 3,4-methylenedioxyethylamphetamine; MDEA), a solid-phase extraction (SPE) method, which can be automated, was applied for the simultaneous determination by GC/MS in human urine. Urine samples (3 mL) and 0.1 M phosphate buffer (1 mL, pH 7.0) were extracted by an automated SPE system. The eluent was evaporated, derivatized with trifluoroacetic anhydride (TFAA), and analyzed by GC/MS. The calibration curves was linear with correlation coefficient ($r^2$) above 0.994 in the ranges of 34.0 (AP), 28.0 (MDA)~1000.0 ng/mL for AP, MDA, and 50.0~2000.0 ng/mL for MA, MDMA, and MDEA. The limits of detection ranged from 4.0 to 10.0 ng/mL, and the limits of quantitation ranged from 12.0 to 34.0 ng/mL. The relative recoveries were 93.5~107.7 %. The precisions and accuracies were 1.9~14.8 % and -8.7~14.8 %, respectively. The present method was successfully applied to identify the MA or Ecstasy (MDMA) abusers in exact as well as rapid.

• KSBB Journal
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• v.18 no.4
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• pp.277-281
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• 2003

The study of growth characteristics for Spirulina platensis were carried out in 400 mL cylindrical photobioreactor and the effects of carbon dioxide concentration and flow rate during the growth of Spirulina platensis were investigated. The results showed that relatively low carbon dioxide concentration and high flow rate forced the growth of Spirulina platensis in experiment conditions. The pH analysis showed that different carbon dioxide concentration might form particular aqueous carbonate system in culture medium and affect the growth of Spirulina platensis. In addition, the possibility of limiting light radiation by cell density was investigated by the analysis of specific growth rate. The result intimated that the cause of decrease of specific growth rate at exponential phase was due to the limitation of light radiation by Spirulina platensis cell density in cylindrical photobioreactor.

• Journal of the Korean Chemical Society
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• v.56 no.2
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• pp.228-235
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• 2012

A $N_2O_2$ Schiff base ligand, N,N'-bis(4-methoxysalicylidene)phenylendiamine (4-$CH_3O$-salphen) was synthesized. Using the 4-$CH_3O$-salphen, the spectrophoto-metric quantitative analysis of Cu(II) ion in aqueous solution was performed. The optimum condition for the quantitative analysis of Cu(II) ion was determined as the following; the concentration of 4-$CH_3O$-salphen is $2.0{\times}10^{-4}\;mol/L$, ratio between solvent DMSO and water is 50/50(v/v), pH is 5.5. After 1 hr water incubation at $55^{\circ}C$ and then the absorbance measurements at 388 nm, a calibration curve (${\varepsilon}=3.6{\times}10^4\;mol^{-1}cm^{-1}$) with a correlation coefficient ($R^2$=0.9963) was obtained in this condition. Using this optimized condition, the quantitative analysis of Cu(II) ion was performed with various samples such as hot spring water, semiconductor factory waste water and treated water from sewage treatment plant. The average value of the measured values agreed well with standard value with a range of 0.6~5.4%. The limit of determination was 31.77 ng/mL ($5.0{\times}10^{-7}\;mol/L$).

• Korean Journal of Food Science and Technology
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• v.38 no.2
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• pp.169-175
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• 2006

Potentiometric biosensor using flow injection analysis system was developed to determine citrate concentration in foods. Biosensor system consisted of sample injector, peristaltic pump, enzyme reactor, carbonate ion selective solid-state electrode, reference electrode, detector, and recorder. Enzyme reactor was prepared with immobilized citrate lyase and oxaloacetate decarboxylase. Carbonate ions produced through enzyme reactions of citrate were potentiometrically detected by ion selective electrode. Optimum conditions for biosensor system were investigated. Interference effect of major sugars and organic acids was less than 5% on citrate biosensor system. Citrate concentrations in fruit juices were determined by biosensor and gas chromatography. No significant difference was observed between two analytical methods. Results indicate citrate biosensor is useful in determining citrate concentration in foods.

• The Korean Journal of Nuclear Medicine
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• v.31 no.1
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• pp.73-82
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• 1997

Regional myocardial blood flow (rMBF) can be noninvasively quantified using N-13 ammonia and dynamic positron emission tomography (PET). The quantitative accuracy of the rMBF values, however, is affected by the distortion of myocardial PET images caused by finite PET image resolution and cardiac motion. Although different methods have been developed to correct the distortion typically classified as partial volume effect and spillover, the methods are too complex to employ in a routine clinical environment. We have developed a refined method incorporating a geometric model of the volume representation of a region-of-interest (ROI) into the two-compartment N-13 ammonia model. In the refined model, partial volume effect and spillover are conveniently corrected by an additional parameter in the mathematical model. To examine the accuracy of this approach, studies were performed in 9 coronary artery disease patients. Dynamic transaxial images (16 frames) were acquired with a GE $Advance^{TM}$ PET scanner simultaneous with intravenous injection of 20 mCi N-13 ammonia. rMBF was examined at rest and during pharmacologically (dipyridamole) induced coronary hyperemia. Three sectorial myocardium (septum, anterior wall and lateral wall) and blood pool time-activity curves were generated using dynamic images from manually drawn ROIs. The accuracy of rMBF values estimated by the refined method was examined by comparing to the values estimated using the conventional two-compartment model without partial volume effect correction rMBF values obtained by the refined method linearly correlated with rMBF values obtained by the conventional method (108 myocardial segments, correlation coefficient (r)=0.88). Additionally, underestimated rMBF values by the conventional method due to partial volume effect were corrected by theoretically predicted amount in the refined method (slope(m)=1.57). Spillover fraction estimated by the two methods agreed well (r=1.00, m=0.98). In conclusion, accurate rMBF values can be efficiently quantified by the refined method incorporating myocardium geometric information into the two-compartment model using N-13 ammonia and PET.

• The Korean Journal of Nuclear Medicine
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• v.28 no.1
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• pp.75-84
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• 1994

The need for assessment of ureteric function in the patient with an obviousely dilated ureter has increased particularly with the added spectrum of asymptomatic patients presenting with hydrone-phrosis and hydroureter on antenatal and perinatal ultrasound. To assess the influence of ureteral status on kidney washout during $^{99m}Tc$-DTPA diuretic renography, ureteral images were reviewed in 80 children referred for hydronephrosis. A scintigraphically abnormal ureter was defined as an intense and continuous image of > 10 min during diuretic renography. Out of them, a total of 16 nephroureteral systems in 12 children with scintigraphically abnormal ureter were analyzed. A diuretic washout index using response half time (t1/2) by linear fitting after lasix injection, was determined on renal (Kt1/2) and ureteral (Ut1/2) curves (diuretic renogram vs. diuretic ureterogram). Diuretic ureterogram curve patterns corresponding to normal (type I), obstructive (II) and non-obstructive (III) cases were described. Compared with X-ray data, diuretic renography was highly sensitive (88%) and specific (99%) for detecting any ureteral abnormality. Despite an obstructive Kt1/2 (>20 min), no patient with an abnormal ureter underwent therapy at the ureteropelvic junction because the hydronephrosis regressed after surgery at the lower level. Our data indicate that the abnormal ureter findings during diuretic renography have to be recognized before therapy for children with hydeonephrosis.

• Journal of Food Hygiene and Safety
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• v.22 no.4
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• pp.370-374
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• 2007

An analytical method for the simultaneous determination of four tetracycline (oxytetracycline, tetracycline, chlortetracycline, doxycycline) in egg samples was developed and validated using liquid chromatography with ultraviolet detection. Egg samples were extracted by the liquid-liquid extraction based on acetonitrile. The chromatographic separation was achieved on a reverse phase C8 column with gradient elution using a mobile phase of 20 mM oxalic acid (pH 1.5)/acetonitrile. The procedure was validated according to the Food Drugs Administration guideline determining accuracy, precision, and limit of detection. Mean recovery of tetracyclines from spiked egg samples (50, 100, 200, 400, and $800{\mu}g/kg$) were 78.8-109.3%. Linearity in concentration range of $50-800{\mu}g/kg$ was obtained with the correlation coefficient $(r^2)$ of 0.994-0.999. The intra- and inter-day precision (relative standard deviation; RSD) was between 0.3-12.8 and 0.2-11.7%, respectively. Limit of detection (LOD) and limit of quantification (LOQ) for the investigated tetracyclines were 30 and $50{\mu}g/kg$ depending on egg samples, respectively. This method was reliable, sensitive, economical and suitable for routine monitoring of tetracycline residues in dairy egg.

• Journal of Food Hygiene and Safety
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• v.23 no.4
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• pp.324-329
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• 2008

An analytical method for the simultaneous determination of nine quinolones (QNs) namely, marbofloxacin, norfloxacin(IS), ciprofloxacin, danofloxacin, enrofloxacin, sarafloxacin, difloxacin, oxolinic acid, and flumequine in flatfish and egg was developed and validated using liquid chromatography with fluorescence detection (LC-FD). The samples were extracted using a traditional liquid-liquid extraction process; deproteinization was accomplished by the addition of trichloroacetic acid and acetonitrile (ACN), and defatting was performed with hexane. Chromatographic separation was achieved on a reverse phase C8 column with gradient elution using a mobile phase of 200 mM ammonium acetate buffer (pH 4.5) and ACN. The proposed method was validated according to the CODEX guideline. Mean recoveries of QNs from flatfish and egg were 89.6-106.5% with relative standard deviations (RSDs) below 15% at three different concentrations of 50, 100 and $500{\mu}g/kg$. Linearity was obtained with a correlation coefficient ($r^2$) of 0.9989-1.0000. The LOD for the investigated QNs was $1-16{\mu}g/kg$ depending on flatfish and egg. The present method can be applied simultaneously to determine QNs in muscle of flatfish and egg.

• Analytical Science and Technology
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• v.28 no.6
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• pp.417-424
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• 2015

In this study, the relationship between selenoprotein concentrations in blood and stomach cancer have been searched for Korean. The concentration of each selenoprotein in blood serum was analyzed and the correlation between the concentration and stomach cancer was studied to find a potential for using Selenium as a biomarker. In concentration determination, a simple calibration curve method was used with the monitoring of m/z 78 without the use of solid phase extraction. This is a lot more simple than the method using SPE with post column isotope dilution. The result obtained from the analysis of CRM BCR-637, 72.20±3.35 ng·g⁻¹, showed similar value of reference value (81±7 ng·g⁻¹). The total concentration of Se for the controlled group, cardiovascular patients group, was 105.70±21.20 ng·g⁻¹. This value was the same as normal healthy person reported earlier. Each selenoprotein concentration of GPx, SelP and SeAlb was 26.12±7.84, 65.15±14.50, 14.43±6.99 ng·g⁻¹, respectively. The distribution of each selenoprotein was 24.7%, 61.6%, and 13.7%, which was similar to the normal person. The result of stomach cancer patients, the total concentration of Se was 76.11±28.12 ng·g⁻¹ and each concentration of GPx, SelP and SeAlb was 15.41±9.01, 50.83±17.91, and 9.87±5.21 ng·g⁻¹, respectively. The total and each selenoprotein concentration level showed significant decrease for the stomach cancer patients. The level of decrease was 41.0% for GPx, 22.0% for SelP, and 31.6% for SeAlb. However, the distribution of each selenoprotein was not much different. Either total Selenium or each selenoprotein could be used as a possible index for the diagnosis of cancer. However, in age group study, it is shown that young age group (30's-40's) did not show much difference.

• Korean Journal of Soil Science and Fertilizer
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• v.22 no.4
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• pp.257-264
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• 1989

In order to study spatial variability of soil chemical properties across the land-partitioned boundary on Hwadong silt clay loam soil (Fine clayey, mixed, mesic family of Aquic Hapludalfs) in the experimental fie ld of the wheat and Barley Research Institute in Suwon, all measured data were analyzed by means of kriging, fractile diagram, smooth frequency distribution, and autocorrelation. Sampling for soil chemical property analysis was made at 225 intersections of 15x 15 grid with 10m interval from three soil depths (0-10cm, 25-35cm, 50-60cm) in the seven patitioned fields. 1. The coefficient of variance (CV) of various chemical properties varied from 5.4 to 72.7%. Soil pH was classified into the low variation group with CV smaller than 10%, while the other chemical properties belonged to the medium variation group with C.V. between 10 and 100% 2. The approximate number of soil samples for the determination of various chemical properties with error smaller than 10% were two for pH, ten for CEC, 15 for exchangeable Ca, 32 for total nitrogen content, 39 for exchangeable Mg, 40 for exchangeable K, 61 for exchangeable Na, 82 for organic matter content, 212 for available phosphate,. 3. Smooth frequency distribution and fractile diagram showed that available phosphate was in log-normal distribution while others were in normal distribution. 4. Serial correlation analysis revaled that the soil chemical properties had spatial dependence between two nearest neighbouring grid points. Autocorrelation analysis of chemcial properties measured between the serial grid points in the direction of south to north following land-partitioned boundary showed that the zone of influence showing stationarity ranged from 20 to 50m. In the direction of east to west accross land-partitioned boundary, the autocorrelogram of many chemical properies showed peaks with the periodic interval of 30m, which were similar to the partitioned land width. This reveals that the land-partitioned boundary causes soil variability.