• Journal of Food Hygiene and Safety
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• v.32 no.5
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• pp.418-423
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• 2017

An analytical method for the determination of dexamethasone (DM) in bovine milk samples was developed and validated using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Milk samples were extracted by the liquid-liquid extraction based on acetonitrile. The chromatographic separation was achieved on a reverse phase $C_{18}$ column with gradient elution using a mobile phase of 0.1% formic acid in 95% acetonitrile. The procedure was validated according to the Ministry of Food and Drug Safety guideline determining accuracy, precision, limit of detection (LOD), and limit of quantification (LOQ). Mean recoveries of DM from spiked milk samples (25, 125, and 1,250 ng/mL) were 98.9-109.6%, and the relative standard deviation was between 1.7 and 4.4%. Linearity in concentration range of 12.5-1,250 ng/mL was obtained with the correlation coefficient ($r^2$) of 0.9997. LOD and LOQ for the investigated DM were 0.15 and 0.5 ng/mL depending on milk samples, respectively. This method was reliable, sensitive, economical and suitable for routine monitoring of DM residues in bovine milk.

• Journal of the Korean Chemical Society
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• v.39 no.12
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• pp.902-909
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• 1995

Detection limit as well as calibration curves on organophosphorus pesticide(dimethoate, diazinon, parathion-methyl, fenitrothion, malathion) and BHCs were measured for evaluation of utility on qualitative or quantitative analysis of pesticides with ion Trap mass spectrometer and quadrupole mass spectrometer. As ionization source, EI and CI were adopted for qualitative analysis of pesticides by comparison of each fragmentation pattern. At the same time, the utility as trace analysis techniques through scan or selected ion monitoring(SIM) mode was evaluated. With ion trap for all pesticides, detection limit(DL, 1 ${\mu}L$ injection) on scan mode was ranged 0.008∼0.225 ng at signal to noise ratio 3. With quadrupole DL on scan mode was ranged 0.23∼3.1 ng over 0.032∼0.68 ng on SIM mode. The calibration curve with ion trap generated good linearity over 0.99 as correlation coefficient. As clean up procedure, Bio Beads S-X3 was used for the separation of oils from five organophosphorous pesticides in flour extractant showing more than 80% as recovery at most cases. In case of BHCs in jinseng with Florisil column, the recovery of pesticides has been 60% to 90%.

• Journal of the Korean Chemical Society
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• v.54 no.5
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• pp.523-532
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• 2010

The proposed method is simple, sensitive and specific Liquid chromatography-tandem mass spectrometry (LCESI-MS/MS) method for the quantification of Entacapone (EA) in human plasma using Entacapone-d10 (EAD10) as an internal standard (IS). Chromatographic separation was performed on Zorbax SB-C18, $2.1{\times}50\;mm$, $5\;{\mu}m$ column, mobile phase composed of 10 mM Ammonium formate (pH 3.0): Acetonitrile (60:40 v/v), with a flow-rate of 0.7 mL/min, followed by Liquid-liquid extraction. EA and EAD10 were detected with proton adducts at m/z $306.1{\rightarrow}233.1$ and $316.3{\rightarrow}233.0$ in multiple reaction monitoring (MRM) positive mode respectively. The method was validated over a linear concentration range of 1.00 - 2000.00 ng/mL with correlation coefficient ($r^2$) $\geq$ 0.9993. Intra and inter-day Precision within 3.60 to 7.30 and 4.20 to 5.50% and Accuracy within 97.30 to 104.20 and 98.30 to 105.80% proved for EA. This method is successfully applied in the bioequivalence study of healthy Indian human volunteers.

• Journal of Korea Water Resources Association
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• v.39 no.2 s.163
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• pp.121-126
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• 2006

Snowmelt effect is identified from the analysis of the relationship between precipitation and groundwater level(GWL) data and Severe drawdown of GWL is observed in drought. Groundwater dam Operation Index (GOI), which is developed for the optimal operation of groundwater dam, is calculated by taking common logarithm of the moving average(MA) of precipitation data for a certain period. The period can vary from watershed to watershed because the period is decided by picking the maximum correlation coefficient between GWL and GOI of several MAs of precipitation. For Ssangchun watershed, the correlation was the strongest when we apply 70 day MA for GOI calculation. Snowmelt effect is considered by applying the temperature change by elevation($0.5^{\circ}C$ decrease per 100m) and examining the areal distribution of the watershed by elevation. Snow event is assumed when the daily average temperature is below $0^{\circ}C$ and snowmelt is assumed when the temperature is above zero degree Celsius. Total snowmelt is assumed for the day. When the snow event is occurred the precipitation data is separated into two components, snow and rainfall. The areal distribution by elevation is used for the calculation in the separation. The correlation between GWL and GOI is higher when we consider snowmelt effect than we neglected it.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.12
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• pp.1753-1757
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• 2012

A new liquid chromatographic tandem mass spectrometric (LC-MS/MS) assay for the quantification of ginsenoside Rb1 in human plasma was developed and validated. The separation was performed on a Agilent C18 column ($4.6mm{\times}150mm$, particle size 5 ${\mu}m$) with a gradient elution of 0.1% formic acid in water and 0.1% formic acid in methanol and a flow rate of 0.9 mL/min. The analyte was determined using electrospray positive ionization mass spectrometry in the multiple reaction monitoring (MRM) mode (m/z 1131.714${\rightarrow}$365.303). Human plasma samples were extracted with acetone : water (50:50) by the liquid-liquid extraction method. The method was linear over the dynamic range of 10~500 ng/mL with a correlation coefficient of r=0.9995. The intra-and inter-day precision over the concentration range of ginsenoside Rb1 was lower than 5.8% (correlation of variance, CV), and the accuracy was between 96.0~104.6%. This LC-MS/MS assay of ginsenoside Rb1 in human plasma is applicable for quantification in a pharmacokinetic study.

• Analytical Science and Technology
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• v.16 no.1
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• pp.32-38
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• 2003

The rapid and sensitive determination method of sildenafil and its related compounds (Vardenafil, Homosildenafil, Tadanafil.) has been investigated using high performance thin layer choromatography (HPTLC). Optimizing separation conditions and simultaneous determination method of these compounds were studied. The calibration curves of those compounds at 254 nm was found to be linear in the range of $1.0{\sim}56.5{\mu}g/mL$, respectively. The detection limts (LOD) and quantification limits (LOQ) of these were found to be $0.8{\sim}1.8{\mu}g/mL$ and $1.0{\sim}2.3{\mu}g/mL$. The coefficient of variation (C.V.) were less than 2.5%. Finally, the present method was applied to determine sildenafil and its related substances in dietary supplement.

• Korean Journal of Food Science and Technology
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• v.38 no.1
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• pp.1-4
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• 2006

Method of analyzing sodium alginate in foods was developed using high performance liquid chromatography (HPLC). HPLC conditions for sodium alginate were: column, MCI GEL $(8\;mm\;i.d{\times}300\;mm)$; mobile phase, deionized water; detector, refractive index detection (sensitivity = 16). Separation of sodium alginate was achieved within 15 min. Sodium alginate showed good linear relationship at 0.1-2.0% range. Correlation coefficient of calibration curve for sodium alginate exceeded 0.999, and detection limit was 0.005%. Recovery rate of sodium alginate in wheat flour dough was 106.67%. This method was successfully applied to analyses of cereals, saccharides, and ice cream, etc. Sodium alginate was detected in chocolate, noodles, and kelp at 0-44.8% range.

• Resources Recycling
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• v.29 no.1
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• pp.43-52
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• 2020

The objectives of this study were to identify the optimal mix of foam concrete with the low-strength and high-flow for the repairing ground subsidence situation emergently by utilizing a large amount of industrial by-products and evaluate the possibility by applying it to the site. The factors of the experiment were the mixing ratio of mixing water and a foaming agent and the mixing ratio of foam over paste volume. The optimal mix identified by the experiment was applied to the field and basic properties were evaluated. The results of the experiment showed that the optimal mixing ratio of mixing water and the foaming agent was 10%. Moreover, when the mixing ratio of pre-foam over paste volume was 170%, it satisfied the target. However, to ensure stable quality when applying to the field, the foam mixing ratio was set 140% for the field application. The field application test of foam concrete with the low-strength and high-flow using an eco-friendly binder satisfied all target performances. Therefore, the possibility of using it as a mixture and construction method for a ground repair system is confirmed. However, there was a quality deviation between the upper part and the lower part due to the separation between foam and paste. Consequently, further studies are needed to improve it.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.703-712
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• 2021

In this study, a formula was derived to calculate the damage impact distance using the Chemical Accident Response Information System (CARIS) so that local governments can decide on the evacuation and notification of 13 types of substances. The National Institute of Chemical Safety selected 16 out of 97 types of accident preparedness substances in 2018 and called them residents' evacuation preparedness substances. In a chemical accident, local governments should prepare for resident notification, such as emergency disaster texts. Using the CARIS in Chungju, this study modeled the damage-affected distances of 13 types of substances for the evacuation of residents. Under all conditions, the coefficient of determination R2 was 0.99 or higher, representing a range of at least 0.9921 to a maximum 0.9999. The relative standard deviation between the damage impact distance obtained using the calculation formula, and the CARIS result was compared. The minimum separation distance was corrected considering the actual chemical accident response situation, and the range was found to be between 0.58 and 5.97%. The damage impact distance can be calculated at the site using the calculation formula derived from the research, and local governments can determine whether to evacuate or notify residents.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.6
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• pp.655-662
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• 2021

This study aimed to estimate exploitable groundwater for the sustainable supply of groundwater in the Jinju region of South Gyeongsang Province. As an integrated hydrologic analysis model, SWAT-MODFLOW was used to estimate the distributed groundwater recharge in consideration of land use and soil distribution. As a result of calibration of the model, the coefficient of determination between the observed flow and the simulated flow was 0.75-0.80, which was good. The simulated groundwater recharge rate showed a spatio-temporal distribution due to heterogeneous watershed characteristics. The amount of groundwater recharge shows lower values over winter and spring, but it increases according to the pattern of precipitation in summer and autumn. The calculated average annual groundwater recharge was compared with the result using the baseflow separation method of natural flow, and the deviation of both results was small, within 3 %, confirming the validity of the estimated groundwater recharge. Exploitable groundwater is defined as the amount of recharge corresponding to low flow with 10 years of return period. Therefore, in this study, 14.2 % of the annual precipitation was found to be exploitable as a result of calculating the amount of recharge at a 10-year frequency using a statistical frequency analysis technique.