• 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.

• YAKHAK HOEJI
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• v.52 no.2
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• pp.93-100
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• 2008

A liquid chromatographic method with tandom spectrometric detection (LC/MS/MS) for the simultaneous determination of doxifluridine and its active metabolite, 5-fluorouracil (5-FU) was developed over the concentration range of $5{\sim}2000$ ng/ml, respectively. Doxifluridine, 5-FU and internal standard, 5-chlorouracil (5-CU), were extracted from liver and intestine tissue via protein precipitation. Acetonitrile was used as the extraction solvent and the supernatant was evaporated and reconstructed in mobile phase. Optimum chromatographic separation was achieved on a Agilent Zorbax $C_{18}$ ($100\;mm{\times}2.1\;mm$, $3.5\;{\mu}m$) column with mobile phase run in isocratic with methanol : water (20 : 80, v/v). The flow rate was 0.2 ml/min with total cycle time of 5 min. The lower limit of quantification was validated at 5.0 ng/ml of liver and intestine tissue, for both doxifluridine and 5-FU, respectively. The intra-day and inter-day precision and accuracy of quality control (QC) samples were <11% coefficient of variation and <7% relative error from theoretical concentration for both analytes. In addition, the special designed stability study was performed, because the metabolism of doxifluridine occurs spontaneously even in ice bath for monkey liver. The stability of doxifluridine in liver and intestine of monkey and beagle dog was compared. It was found that bioanalytical validation could not be performed for the monkey liver; however, beagle dog's liver has relatively low speed of metabolism compared to monkey liver and instead of monkey liver, beagle dog's liver could be used for the validation. Bioanalytical validation could be performed in monkey intestine. Eventually, this developed method for liver and intestine will be useful in support of the toxicokinetic and pharmacokinetic studies of doxifluridine and 5-FU.

• Bulletin of the Korean Chemical Society
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• v.33 no.11
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• pp.3665-3670
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• 2012

Metal-p-$NH_2$-Bn-DOTA (paraammionobenzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid: ABDOTA) complex was synthesized and purified for bio-tagging to quantify biological target materials using laser ablation (LA)-ICP-MS. Since the preparation of a pure and stable tagging complex is the key procedure for quantification, magnetic particles were used to purify the synthesized metal-ABDOTA complex. The magnetic particles immobilized with the complex attracted to a permanent magnet, resulting in fast separation from free un-reacted metal ions in solution. Gd ions formed the metal-complex with a higher yield of 64.3% (${\pm}3.9%$ relative standard deviation (RSD)) than Y ions, 52.3% (${\pm}2.5%$ RSD), in the pH range 4-7. The complex bound to the magnetic particles was released by treatment with a strong base, of which the recovery was 81.7%. As a reference, a solid phase extraction (SPE) column packed with Chelex-100 resin was employed for separation under similar conditions and produced comparable results. The tagging technique complemented polydimethylsiloxane (PDMS) microarray chip sampling in LA-ICP-MS, allowing determination of small sample volumes at high throughputs. For application, immunoglobulin G (IgG) was immobilized on the pillars of PDMS microarray chips and then tagged with the prepared Gd complex. IgG could then be determined through measurement of Gd by LA-ICP-MS. A detection limit of 1.61 ng/mL (${\pm}0.75%$ RSD) for Gd was obtained.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.1
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• pp.77-84
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• 2006

Since the long-term exposure of mutans streptococci to xylitol is known to select for xylitol-resistant $(X^R)$ natural mutants, the occurrence and survival of such $(X^R)$ strains were performed in batch culture methods. The aim of the study was to compare the differentiation and quantification of mRNA expression of the gtf genes of $X^R\;and\;X^S$ mutans streptococci. Using a real-time reverse-transcription polymerase chain reaction, the expression of each gtf was determined. In $X^R$ strains, the relative levels of transcription of gtfB and gtfC were decreased while that of gtfD was increased, suggesting the presence of independent promoters. It also suggested that mutation related to production of glucosyltransferase occurred under the exposure of xylitol could explain the caries-preventive mechanisms of xylitol.

• International Journal of Industrial Entomology and Biomaterials
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• v.23 no.2
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• pp.223-229
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• 2011

Cyclophilins are originally identified as cytosolic binding protein of the immunosuppressive drug cyclosporine A. They have an activity of peptidyl prolyl cis/trans-isomerases (PPIase), which may play important roles in protein folding, trafficking, assembly and cell signaling. In this study, we report the cloning and characterization of a Bombyx mori cyclophilin A (bCypA) cDNA. The full-length cDNA of bCypA consist of 947 nucleotides with a polyadenylation signal sequence AATAAA and contain an open reading frame of 498 nucleotides encoding a polypeptide of 166 amino acids. The deduced amino acid sequence of bCypA shares a central peptidyl prolyl cis/trans-isomerase and a cyclosporin-A-binding domain with other cyclophilin sequences. Relative quantification real-time (RT) PCR analysis shows that mRNA transcripts of bCypA are detected in all the investigated tissues and highest expression level in the skin of 3-day-old 5 instar larva. Also, bCypA had PPIase activity on the proline-containing peptides. Accordingly, we suggest that bCypA is a new member of the cyclophilin A (CyPA) family and will be useful for quality control of bioactivity recombinant proteins with proline-containing peptides.

• Preventive Nutrition and Food Science
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• v.19 no.4
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• pp.321-326
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• 2014

In this study, we developed a method to quantify esculetin (6,7-dihydroxycoumarin) in plasma and tissues using HPLC coupled with ultraviolet detection and measured the level of esculetin in rat plasma after oral administration. The calibration curve for esculetin was linear in the range of 4.8 ng/mL to 476.2 ng/mL, with a correlation coefficient ($r^2$) of 0.996, a limit of detection value of 33.2 ng/mL, and a limit of quantification value of 100.6 ng/mL. Recovery rates for the 95.2 ng/mL and 190.5 ng/mL samples were 95.2% and 100.3%, within-runs and 104.8% and 101.0% between-runs, respectively. The relative standard deviation was less than 7% for both runs. In the pharmacokinetic analysis, the peak plasma esculetin level was reached 5 min after administration ($C_{max}=173.3ng/mL$; $T_{1/2}=45min$; $AUC_{0{\sim}180min}=5,167.5ng{\cdot}min/mL$). At 180 min post-administration (i.e., after euthanasia), esculetin was only detectable in the liver ($30.87{\pm}11.33ng/g$) and the kidney ($20.29{\pm}7.02ng/g$).

• Analytical Science and Technology
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• v.28 no.4
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• pp.299-307
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• 2015

In May 2012, a safety hazard issue arose because some kiwifruit growers in New Zealand had sprayed streptomycin to prevent kiwifruit canker. Therefore, for food safety management, analytical methods to determine streptomycin residues in kiwifruits are required. We developed an analytical method to determine streptomycin residues in kiwifruit samples using liquid chromatograph tandem mass spectrometer (LC-ESI-MS/MS). Streptomycin residues in samples were extracted using 1% formic acid in methanol, centrifugation for 10 min, and subsequent supernatant filtration. Purified samples were subjected to LC-ESI-MS/MS to confirm presence of and quantify streptomycin residues. Average streptomycin recoveries (6 replicates each sample) were in the range of 94.8%-110.6% with relative standard deviations of <10%. The linearity of the concentration range of 0.01-5.0 mg/kg using a matrix-matched calibration gave R² = 0.9995. The limit of quantification (LOQ) was 0.01 mg/kg. Results showed that our analytical method is rapid, simple, and sensitive, with easy sample preparation.

• Toxicological Research
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• v.26 no.2
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• pp.149-155
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• 2010

The pesticide trichlorfon is readily degraded under experimental conditions to dichlorvos. A method has therefore been developed by which residues of trichlorfon in milk are determined as dichlorvos, using gas chromatography with ${\mu}$-electron capture detection. The identification of dichlorvos was confirmed by mass spectrometry. Milk was extracted with acetonitrile followed by centrifugation, freezing lipid filtration, and partitioning into dichloromethane. The residue after partitioning of dichloromethane was dissolved in ethyl acetate for gas chromatography. Recovery concentration was determined at 0.5, 1.0, and 2.0 of times the maximum permitted residue limits (MRLs) for trichlorfon in milk. The average recoveries (n = 6) ranged from 92.4 to 103.6%. The repeatability of the measurements was expressed as relative standard deviations (RSDs) ranging from 3.6%, to 6.7%. Limit of detection (LOD) and limit of quantification (LOQ) were 3.7 and $11.1{\mu}g/l$, respectively. The accuracy and precision (expressed as RSD) were estimated at concentrations from 25 to $250{\mu}g/l$. The intra- and inter-day accuracy (n = 6) ranged from 89.2% to 91% and 91.3% to 96.3%, respectively. The intra- and inter-day precisions were lower than 8%. The developed method was applied to determine trichlorfon in real samples collected from the seven major cities in the Republic of Korea. No residual trichlorfon was detected in any samples.

• Applied Chemistry for Engineering
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• v.30 no.5
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• pp.591-596
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• 2019

A recently developed propellant, ammonium dinitramide (ADN, $NH_4N(NO_2)_2$ is stable and safe at an ambient condition. However, it requires high purity for practical applications. A very little quantity of foreign impurities in ADN may cause clogging of thruster nozzles and catalyst poisoning for the use of a liquid propellant. Thus, several purification processes for precipitated ADN particles such as repetition extraction, activated carbon adsorption and low-temperature extraction were presented in this study. The purifying methods helped to improve the chemical purity as evaluated by FT-IR and UV-Vis spectroscopy in addition to ion chromatography (IC) analyses. Among the purification processes, adsorption was found to be the best, showing a final purity of 99.8% based on relative quantification by IC. Thermal analysis revealed an exothermic temperature of $148^{\circ}C$ for the synthesized liquid monopropellant, but rose to $188^{\circ}C$ when urea was added.

• Journal of Applied Biological Chemistry
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• v.62 no.2
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• pp.129-135
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• 2019

Salvia miltiorrhiza Radix is cultivated in Korea and China and is traditionally used to treat cardiovascular diseases. In this study, we developed and validated a quantitative analysis method for S. miltiorrhiza Radix using high-performance liquid chromatography (HPLC). Identification was performed using ultra performance liquid chromatography-tandem mass spectrometry. For quantitative analysis, we used seven marker compounds. Separation conditions for HPLC were optimized using an ODS column with gradient conditions of 1% formic acid in distilled water and 1% formic acid in acetonitrile, with a flow rate of 0.8 mL/min and a detection wavelength of 280 nm. This method showed good linearity ($R^2=0.9998$), precision (relative standard deviation ${\leq}3.3%$), accuracy (recovery of 94.16-102.89%), limit of detection ($7.53{\mu}g/mL$), and limit of quantification ($23.71{\mu}g/mL$). This approach successfully quantified marker compounds in S. miltiorrhiza Radix. The individual marker compounds were identified by comparing the molecular masses and retention times with does standard compounds. Marker compound contents of S. miltiorrhiza Radix were investigated with different cultivation regions. Seven marker compounds were detected and quantified in all samples. Among them, salvianolic acid B showed the highest contents and it ranged from 4.13 to 7.15%. The salvianolic acid B content (7.15%) of marker compound was the highest in Bonghwa, and the tanshinone IIA content (1.90%) was the highest in Pohang. The results of marker compounds and developed method were intended to provide a favorable reference for the study of S. miltiorrhiza Radix from different regions of Korea.