• Journal of the Korean Vacuum Society
• /
• v.6 no.4
• /
• pp.293-297
• /
• 1997

Using trace etching method in this study, we measure the energy of argon ions generated in VEBA System which is composed of Marx Generater and Pulse Forming Line. In this system the electron beam of 240 kV, 30 kA, 60 ns is generated. Argon ions are formed through the electron beam ionization of a gas cloud injected by a fast puff valve. Thus argon ions are accelerated into vacuum drift tube by a virtual cathode and seperated with electron beam, consequently, they heat the trace etching plates made of aluminum thin films. The energy of argon ions are determined by the number of aluminum thin films penetrated by the ions. This experimental value corresponds with the theoretical value.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.10 no.4
• /
• pp.15-22
• /
• 2002

As the emission regulations on the automobiles have been increasingly stringent, precise control of air/fuel ration is one of the most important issues on the gasoline engines. Although many researches have been carried out to identify the fuel transport phenomena in the port fuel injection gasolines, mixture preparation in the cylinder has not been fully understood due to the complexity of fuel film behavior, In this paper, the mixture preparation during cold engine start is studied by using a Fast Response Flame ionization Detector.(FRFID) In order to estimate the transportation of injected fuel from the intake port into cylinder, the wall wetting fuel model was used. The two coefficient($\alpha$,$\beta$) of the wall-wetting fuel model was determined from the measured fuel mass that was inducted into the cylinder at the first cycle after injection cut-in. $\alpha$( ratio of directly inducted fuel mass into cylinder from injected fuel mass) and $\beta$ (ratio of indirectly inducted fuel mass into cylinder from wall wetted fuel film on the wall) was increased with increasing cooling water temperature. To reduce a air/fuel ratio fluctuation during cold engine start, the appropriate fuel injection rate was obtained from the wall wetting fuel model. Result of air/fuel ratio control, air/fuel excursion was reduced.

• Proceedings of the Korean Society of Food Hygiene and Safety Conference
• /
• 2001.10a
• /
• pp.140-140
• /
• 2001

A sensitive analytical method based on gas chromatograpy-mass spectrometry with a selected ion monitoring (GC/MS-SIM) with the purge-and-trap concentration and with headspace method (in limited applications) was developed for determining of epichlorohydrin in canned beverages coated with epoxy resin. The calibration curve in the range of $0.5\sim50ng$ had correlation coefficient greater than 0.998 and a detection limit of $0.l\mug/L$ was obtained using a sample volume of 20ml. The predominant ions of epichlorohydrin produced in MSD using electron ionization(EI) were m/z 57 ([M-CI]+) and 62/64 $([M-CH_2O]+)$. In survey of epichlorohydrin in thirty commercial canned beverage samples, none of them was detected.

• Mass Spectrometry Letters
• /
• v.2 no.3
• /
• pp.61-64
• /
• 2011

Matrix Assisted Laser Desorption/Ionization-Time-of-Flight mass spectrometry (MALDI-TOF-MS) is the most widely used MS technique for glycan analysis. However, the poor point-to-point and sample-to-sample reproducibility becomes a limit in glycan biomarker research. A prespotted MALDI plate which overcomes the large crystal formation of 2,5-dihydroxybenzoic acid (DHB) has been developed and applied for glycan analysis. A homogeneous matrix coated surface without a crystal structure was formed on a hydrophilic/ hydrophobic patterned surface using a piezoelectric device. The reproducible MALDI-TOF-MS data have been presented using MALDI imaging of beer glycan as well as serum glycan eluted from 10% and 20% ACN elution fractions. The glycan profile from the serum glycan by MALDI-TOF-MS with a DHB prespotted plate was highly conserved for 10 different spectra and the coefficient of variations of significant ion peaks of MALDI data varies from 3.59 to 19.95.

• Korean Journal of Plant Resources
• /
• v.30 no.6
• /
• pp.693-698
• /
• 2017

The quality control of natural products is principal key to guarantee the Good Manufacturing Practices (GMP) and Good Clinical Practices (GCP) for the functional food, pharmaceuticals and cosmeceuticals in the industry. In this study, we examined the quantitative analysis of berberine as marker substance of Coptidis Rhizoma by high performance liquid chromatography-photodiode array detector (HPLC-DAD). The HPLC method was validated and met all the requirements for the quality control analysis recommended by FDA and ICH. The berberine was separated on a Xterra $C_{18}$ column ($5{\mu}m$, $4.6{\times}250mm$) using mobile phase consisting of distilled water and acetonitrile with $KH_2PO_4$ (3.4 g) and $Na_2SO_4$ (1.7 g). Calibration curve of berberine has been estimated (y = 42293.47x-41589 with the correlation coefficient 0.9999). The amount of berberine was calculated as 4.25%. And berberastine, palmatine, columbamine, jatrorrhizine, epiberberine, berberine and coptisine in the Coptidis Rhizoma were identified by high performance liquid chromatography - electrospray ionization-mass spectrometer (HPLC-ESI-MS) method.

• Food Science of Animal Resources
• /
• v.37 no.6
• /
• pp.847-854
• /
• 2017

A rapid, sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the simultaneous determination of four barbiturates (phenobarbital, pentobarbital, amobarbital and secobarbital) in raw milk. The barbiturates were extracted using liquid-liquid extraction, ultrasonication and centrifugation, and purified on an SPE column. Analytes were separated by HPLC on a CSH C18 column eluted using an acetonitrile-water system with a linear gradient dilution programme, and detected by MS/MS. The recoveries of the barbiturates were 85.0-113.5%, and the intra- and inter-assay RSDs were less than 9.8% and 7.3%, respectively. The limit of detection was 5 ng/mL for all four of the barbiturates. The analytical method exhibited good linearity from 10 to 1000 ng/mL; the correlation coefficient ($r^2$) was greater than 0.9950 for each barbiturate. This method was also applied to the determination of barbiturates in real milk samples and was found to be suitable for the determination of veterinary drug residues in raw milk.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.7 no.8
• /
• pp.116-122
• /
• 1999

According to the stringent exhaust emission regulation, precise control of air fuel ratio is one of the most important issues on gasoline engine. Although many researches have been carried out to identify the fuel transport phenomena in a port fueled gasoline engine, complexity of fuel film behavior in the intake port makes it difficult. The fuel film behavior was investigated recently by using visualization method and these gave us qualitative understanding. The purpose of this study is to estimate of wall wetting fuel in the intake port and the inducted fuel mass was predicted by using wall wetting fuel model . The model coefficient($\alpha$,$\beta$) and fuel film mass on the port wall were determined from measured in-cylinder HC concentration using FRFID after injection off. The fuel film mass was increased, but $\alpha$(ratio of directly inducted fuel mass into cylinder from injected fuel mass) was decreased with increasing load at the same engine speed. $\beta$is nearly constant value(0.8~0.9). when injected fuel mass is varied at 1500rpm , the calculated air fuel ratio using well wetting fuel model was nearly the same as measured by UEGO.

• Archives of Pharmacal Research
• /
• v.27 no.12
• /
• pp.1202-1206
• /
• 2004

A rapid, sensitive and selective liquid chromatography-tandem mass spectrometric (LC-MS/ MS) method for the determination of lithospermic acid B (LSB) in rat serum was developed. LSB and internal standard, 7-hydroxy-3-phenyl-chromen-4-one (HPC) were extracted from rat serum with methyl-tert-butyl ether at acidic pH and analyzed on a Luna $C_8$ column with the mobile phase of acetonitrile-ammonium formate (10 mM, pH 6.5) (50:50, v/v). The analytes were detected using a negative electrospray ionization tandem mass spectrometry in the multiple- reaction-monitoring mode. The standard curve was linear $(r^2 = 0.997)$ over the concentration range of 10.0-500 ng/mL. The coefficient of variation and relative error for intra- and interassay at three QC levels were 1.1~6.2% and -10.3~-2.7%, respectively. The recovery of LSB from serum sample ranged from 73.2 to 79.5%, with that of HPC (internal standard) being 75.1 %. The lower limit of quantification for LSB was 10 ng/mL using 50 ${\mu}L$ of serum sample.

• Journal of the Korean Chemical Society
• /
• v.61 no.1
• /
• pp.25-28
• /
• 2017

Solvolyses with the reaction center being the sulfur of 4-(chlorosulfonyl)biphenyl ($C_6H_5C_6H_4SO_2Cl$, 1) was studied under solvolytic conditions and the extended Grunwald-Winstein equation was applied. The thirty five kinds of solvents gave a reasonable extended Grunwald-Winstein plot with a correlation coefficient (R) of 0.940. The sensitivity values (l = 0.60 and m = 0.47) of 1 were smaller than those obtained for benzenesulfonyl chloride ($C_6H_5SO_2Cl$, 2; l = 1.10 and m = 0.61) proposed to undergo dissociative $S_N2$ mechanism. These l and m values for the solvolyses of 1 can be considered to support a $S_N2$ pathway with some ionization reaction. The activation parameters, ${\Delta}H^{\neq}$ and ${\Delta}S^{\neq}$, were determined and they are also in line with values expected for a bimolecular reaction. The kinetic solvent isotope effect (KSIE) of 1.26 is also in accord with a bimolecular mechanism, probably assisted by general-base catalysis.

• KSBB Journal
• /
• v.30 no.4
• /
• pp.141-147
• /
• 2015

The convenient determination of methylsulfonylmethane (MSM) for a commercially available dietary supplement was developed using gas chromatography (GC)-flame ionization detector (FID). Chromatography was performed on a capillary column ($0.32mm\;I.D{\times}30m$, $0.25{\mu}m$) coated with dimethylpolysiloxane using diethylene glycol methyl ether as an internal standard. The performance characteristics of GC were evaluated in terms of selectivity, linearity, precision, accuracy, recovery, limit of detection (LOD) and limit of quantification (LOQ). The calibration curve was highly linear (the coefficient of determination: 0.9979) within the concentration range of $10.0{\sim}800.0{\mu}g/mL$ for MSM. The recoveries for three fortified concentrations were 96.7~97.1%, 96.6~97.3% and 96.8~97.2%, respectively. The LOD and LOQ of the method were $0.29{\mu}g/mL$ and $0.97{\mu}g/mL$, respectively. All obtained results were acceptable according to the guidelines of the Association of Official Analytical Chemists for dietary supplements. Thus, the validated analytical method using the GC-FID system is suitable for the determination of MSM in dietary supplement formulations for quality control.