• Bulletin of the Korean Chemical Society
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• 제35권3호
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• pp.821-827
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• 2014

An isotope dilution liquid chromatography tandem mass spectrometry (ID LC-MS/MS) method has been developed and applied to the determination of arsenobetaine (AsB, ${(CH_3)_3}^+AsCH_2COO^-$) from oyster candidate certified reference material (CRM). The exact matching isotope dilution approach was adopted for accurate determination of AsB using $^{13}C_2$-labeled AsB as an internal standard. Efficiencies of different AsB extraction methods were evaluated using a codfish reference material and a simple sonication method was selected as the method of choice for the certification of the oyster candidate CRM. The hydrophilic interaction liquid chromatography (HILIC) combined with electrospray ionization tandem mass spectrometry (ESI/MS/MS) in selected reaction monitoring (SRM) mode was optimized for adequate chromatographic retention and robust quantification of AsB from codfish and oyster samples. By analyzing 12 subsamples taken from each 12 bottles systematically selected from the whole oyster CRM batch, the certified value of AsB was determined as $6.60mg{\cdot}kg^{-1}{\pm}0.31mg{\cdot}kg^{-1}$ and it showed excellent between-bottle homogeneity of less than 0.42%, which is represented by relative standard deviation of 12 bottles from the CRM batch. The major source of uncertainty was the certified value of the AsB standard solution.

• Mass Spectrometry Letters
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• 제11권2호
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• pp.36-40
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• 2020

Untargeted metabolomics is a useful tool for drug development focusing on novel chemotherapeutic and chemopreventative agents against cancer cells. In recent years, quadrupole time of flight liquid chromatography-mass spectrometry (Q-TOF LC/MS)-based untargeted metabolomic approaches have gained importance to evaluate the effect of these agents at the molecular level. The researchers working on cell culture studies still do not apply standardized methodologies on sample preparation for untargeted metabolomics approaches. In this study, the rough and wet lysis techniques performed on MCF-7 breast cancer cells were compared with each other via the Q-TOF LC/MS-based metabolomic approach. The C18 and hydrophilic interaction liquid chromatography (HILIC) columns were used for the separation of the metabolites in MCF-7 cell lysates. 505 peaks were detected through the HILIC column and 551 peaks were found through the C18 column for the wet lysis technique. This situation supported by the base peak chromatograms showed that the wet lysis technique allowed us to extract higher number of non-polar metabolites. Almost equal number of metabolites was found for the C18 and HILIC columns (697 peaks for the HILIC column and 695 peaks for the C18 column) when the rough lysis technique was used. However, the intensities of polar metabolites were higher for the rough lysis technique on base peak chromatograms for both the HILIC and C18 columns. Although cell lysis technique, which is the first step in the sample preparation for cell culture studies, does not cause dramatic differences in the number of the detected metabolite peaks, it affects the polar and non-polar metabolite ratio significantly. Therefore, it must be considered carefully especially for in vitro drug development studies.

• 분석과학
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• 제8권4호
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• pp.519-527
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• 1995

The retention mechanism of Ni(II)-${\alpha}$-isonitroso-${\beta}$-diketone imine chelates in reversed-phase HPLC has been studied by examining the effect of temperature, mobile phase composition in acetonitrile-water mixture, and molecular structure on retention. The empirical retention equation was investigated to evaluate the properties of S (hydrophilic index). The value of the S index of the Ni(II) chelates decrease with the increasing column temperature and a linear relationship between S and log $k{_w}^{\prime}$ has been found. The results showed that the S index is influenced by the interaction between Ni(II) chelates and mobile phase. Molecular properties, van der Waals molar volume, polarizability and dipole moment, of the Ni(II) chelates were calculated by Cerius 2 program and the calculations were performed at Universal Force Field (UFF) model. The S value and log $k{_w}^{\prime}$ increase with decreasing the dipole moment of Ni(II) chelates.

• Bulletin of the Korean Chemical Society
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• 제35권1호
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• pp.197-203
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• 2014

A rapid, accurate and precise method for the determination of 22 amino acids in Isatidis Radix by Hydrophilic Interaction Ultra-High-Performance Liquid Chromatography Coupled with Triple-Quadrupole Mass Spectrometry (HILIC-UPLC-MS/MS) was established. Chromatographic separation was carried out on a Acquity UPLC BEH Amide column ($2.1mm{\times}100mm$, $1.7{\mu}m$) with gradient elution of acetonitrile (containing 0.05% formic acid and 2 mM ammonium formate) and water (containing 0.15% formic acid and 10 mM ammonium formate) at a flow rate of 0.4 mL/min; Waters Xevo$^{TM}$ TQ worked in multiple reaction monitoring mode. All components were separated in 17 min. All calibration curves were linear ($R^2$ > 0.991) over the tested ranges. The limits of detection (LOD) and limits of quantitation (LOQ) for these compounds were 0.21-79.55 and 0.72-294.23 ng/mL, respectively. The average recoveries were in the range of 93.75-104.16% with RSD value less than 6.56%. Therefore, this method could be an alternative assay for the determination of 22 amino acids in Isatidis Radix due to its rapidness, sensitivity, less sample and solvent consumption.

• 한국산업보건학회지
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• 제9권1호
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• pp.23-40
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• 1999

The analysis of thiodiglycolic acid in urine has been used as an index of biological exposure to vinyl chloride. Unfortunately thiodiglycolic acid has a strong hydrophilic character, because it has two carboxylic groups, so that it can only be extracted with organic solvent with a great difficulty. Underivatized thiodiglycolic acid tends to tail because of non-specific interaction with the inert support. Therefore, esterification is the obvious first choice for derivatization of thiodiglycolic acid, particularly for gas chromatography. In this study, the focus of interest is to compare two method of esterifications (methylation and silylation). Methylation is to make the methyl ester of thiodiglycolic acid by reaction with diazomethane. Silylation is to make the trimethylsilyl ester of thiodiglycolic acid by reaction with N-trimethylsily-ldiethylamine. The results and conclusions are as the following: 1. The detection limit (sensitivity) of methylated thiodiglycolic acid was $5.00{\mu}g/m{\ell}$ and silylated thiodiglycolic acid was $3.07{\mu}g/m{\ell}$ by gas chromatography with flame ionization detector. 2. The optimal liquid-liquid extraction of thiodiglycolic acid was as following: To each of the tubes, $15m{\ell}$ of urine, concentrated sulfuric acid (pH 1 - 2) and 5 gsodium sulfate were added. The samples was extracted three times with $5m{\ell}$ ethylacetate each time. 3. The methylated thiodiglycolic acid was more stable than silylated thiodiglycolic acid in extractional solvent which contained humidity. 4. The precision (pooled coefficient of variation for 4 days) of the analysis was 0.07324 in methylated thiodiglycolic acid with external standard calibration, and 0.07033 in methylated thiodiglycolic acid with internal standard calibration. 5. The precision (pooled coefficient of variation for 4 days) of the analysis was 0.10914 in silylated thiodiglycolic acid with external standard calibration, and 0.13602 in silylated thiodiglycolic acid with internal standard calibration. From the above results, the analysis of methylated thiodiglycolic acid was more sensitive (limit of detection) than silylated thiodiglycolic acid by gas chromatography. However, the methylated thiodiglycolic acid was stable in the humidity and was separated sharply on chromatogram. Also, analysis of methylated thiodiglycolic acid was more precise (pooled coefficient of variation for 4 days) than silylated thiodiglycolic acid. In conclusion, it is established that the analysis of methylated thiodiglycolic acid is appropriate for biological monitoring of exposure to vinyl chloride.

• 한국식품영양과학회지
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• 제37권5호
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• pp.612-617
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• 2008

우리나라 남해안 연안에 서식하는 복섬(Takifugu niphobles) 간장의 TTX유도체들을 활성탄 칼럼을 이용하여 부분 정제하고, Hydrophilic Interaction Liquid Chromatography(HILIC)를 사용한 LC/MS(SIM mode)로 분석하였으며, pH와 가열 조건에 따른 독성 변화를 조사하고 복섬 fillet으로 복국 조리시 독성의 분포를 조사하였다. 복섬 간장의 독성분은 LC/MS에 의하여 7개의 성분이 분석되었으며, 각 성분의 함량과 조성은 5,6,11-trideoxyTTX(34.0%, 1,029.6nmol/g), 6,11-dideoxyTTX(29.3%, 887.6 nmol/g), TTX (22.1%, 667.8 nmol/g), 4,9-anhydroTTX(11.2%, 339.3nmol/g), 11-deoxyTTX＋5-deoxyTTX(2.6%, 78.6 nmol/g), 4-epiTTX(0.8%, 23.6 nmol/g), 5,6,11-trideoxyTTX(34.0%), 6,11-dideoxyTTX(29.3%), TTX(22.1%), 4,9-anhydroTTX (11.2%), 4-epiTTX(0.8%)이었다. 복섬 간장 추출물 희석액의 독성은 pH에 따라 크게 변하여 pH 3에서 8.4 MU/mL로 최고의 독성을 나타내었고, 알칼리로 갈수록 독성이 감소하여 pH 10에서는 pH 3의 1/7(1.4 MU/mL)을 나타내었다. 각각의 pH(pH 5, 7, 9)에서 $80^{\circ}C,\;100^{\circ}C,\;115^{\circ}C$를 유지하며 가열 시 온도는 높을수록, 시간은 길수록 독성은 감소하였다. 특히, 산성이나 중성에서는 독성이 완만하게 감소하는 경향을 보였으나, 알칼리 영역인 pH 9에서는 가열 10분 후에 $80^{\circ}C$의 경우라도 최초 독성(79 MU/mL)이 1/2 이하로 급격히 감소하였으며, $115^{\circ}C$에서는 완전 소멸하였다. 복섬 개체별 fillet 중의 총 독량은 $43.2{\sim}106.7$ MU로 개체에 따라서 2.5배까지 독량의 차이를 나타내었으며, 복섬 가식부에 3배량의 물을 가하여 10분간 끓일 경우 총 독량의 $64{\sim}78%$는 국물 중으로 용출되어 나와 육에 남아있는 것보다 독성이 강하였다.