• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.3
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• pp.189-201
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• 2012

Radiocarbon is a powerful tool for studies of carbon cycling in the ocean. Development of measurement technology of accelerator mass spectrometry has enabled researchers to measure radiocarbon even in specific compounds. In this paper, a brief introduction on radiocarbon measurement and reporting of radiocarbon data is provided. Researches that used radiocarbon measurements on bulk organic matter, organic compound classes, and specific organic compounds are reviewed. Examples include works to understand the cycling of particulate and dissolved organic matter, biochemical composition of particulate organic matter, post-depositional transport of sedimentary organic matter, selective incorporation of fresh organic matter by benthic organisms, chemoautotrophy by archaea, and sources of halogenated chemical compounds found in marine mammals.

• Bulletin of the Korean Chemical Society
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• v.25 no.10
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• pp.1508-1512
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• 2004

A gas chromatography/mass spectrometric (GC/MS) method has been developed for the determination of trace mono-n-butyltin (MBT), di-n-butyltin (DBT), and tri-n-butyltin (TBT) compounds in sediments. Samples were extracted by 10% acetic acid in methanol containing 0.03% tropolone and were then derivatized for GC/MS analysis. Ethylation by sodium tetraethylborate and phenylation by sodium tetraphenylborate were evaluated as a derivatization reaction of the organotins in sample extract. n-Hexane was added into reaction media in the beginning of the reaction for the continuous extraction of derivatized organotins. Ethylation requires less than 2 hours to get proper derivatization yields for MBT, DBT, and TBT altogether and produces relatively low amounts of side reaction products. Compared to ethylation, phenylation requires much longer time but provides relatively lower yield and produces considerable amounts of side reaction products. Therefore, the ethylation reaction was applied for the analysis of organotin compounds in sediment. An isotope dilution mass spectrometric (IDMS) method based on GC/MS has been applied to the accurate determination of DBT compounds in the sediments. The IDMS results from the analyses of sediment samples showed a reasonable repeatability and a good agreement with the values obtained by IDMS based on liquid chromatography/induced coupled plasma/mass spectrometry.

• Journal of Korean Society on Water Environment
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• v.32 no.6
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• pp.649-669
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• 2016

This study explored the analytical conditions for 21 veterinary antibiotics which have been popularly sold in South Korea in 2014 but have not yet been targeted in EPA method 1694. Most of the selected antibiotics were separated by a reverse-phase C18 column with a combination of (buffered) water and organic polar solvent, which was commonly methanol and acetonitrile in the gradient elution mode. Volatile additives such as formic acid, ammonium acetate and ammonium formate were usually added to the mobile phases to minimize asymmetrical and tailing of antibiotics' peaks and to increase their ionization in mass spectrometry. The analytical methods of aminoglycoside antibiotics were distinct from those of the other antibiotics in terms of adoption of ion-pair chromatography (IPC) and hydrophilic interaction liquid chromatography (HILIC) capable of retaining and separating extremely polar compounds due to their hydrophilicity. Trifluoroacetic acid or heptafluorobutyric acid was frequently added to the mobile phase as an ion-pair reagent for the IPC. Tandem mass spectrometry was numerously applied to the detection of antibiotics using positive electrospray ionization (ESI) and the selected reaction monitoring (SRM) mode. All reviewed analytical methods had been/were validated by evaluating recovery, limits of detection and quantification, decision limit or detection capability of the methods.

• Journal of Genetic Medicine
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• v.9 no.1
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• pp.42-46
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• 2012

Short-chain acyl-CoA dehydrogenase deficiency (SCADD; OMIM # 201470) is an autosomal recessive inborn error of mitochondrial fatty acid ${\beta}$-oxidation, presenting with a variety of clinical signs and symptoms. Developmental delay, hypertonia or hypotonia, ketotic hypoglycemia, and epilepsy are most frequently reported. In general, patients diagnosed through newborn screening have shown normal growth and development in contrast to those diagnosed as a result of clinically initiated evaluations. Here, the case of an asymptomatic Korean newborn with SCADD identified by tandem mass spectrometry is reported. The patient showed an elevated concentration of butyrylcarnitine detected on newborn screening. Urinary excretion of ethylmalonic acid was elevated by urine organic acid analysis. To confirm the diagnosis of SCADD, a direct sequencing analysis of 10 coding exons and the exon-intron boundaries of the ACADS gene were performed. Genetic analysis of ACADS showed the following novel compound heterozygous missense mutations: c.277C>A (p.Leu93Ile) on exon3 and c.682G>A (p.Glu288Lys) on exon6. These results will provide further evidence of mutational heterogeneity for SCADD.

• Journal of Ginseng Research
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• v.48 no.4
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• pp.366-372
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• 2024

Background: The biological activity and pharmacological effects of rare ginsenosides have been proven to be superior to those of the major ginsenosides, but they are rarely found in ginseng. Methods: Ginsenoside Rb1 was chemically transformed with the involvement of methanol molecules by a synthesized heterogeneous catalyst 12-HPW@MeSi, which was obtained by the immobilization of 12-phosphotungstic acid on a mesoporous silica framework. High-performance liquid chromatography coupled with mass spectrometry was used to identify the transformation products. Results: A total of 18 transformation products were obtained and identified. Methanol was found to be involved in the formation of 8 products formed by the addition of methanol molecules to the C-24 (25), C-20 (21) or C-20 (22) double bonds of the aglycone. The transformation pathways of ginsenoside Rb1 involved deglycosylation, addition, elimination, cycloaddition, and epimerization reactions. These pathways could be elucidated in terms of the stability of the generated carbenium ion. In addition, 12-HPW@MeSi was able to maintain a 60.5% conversion rate of Rb1 after 5 cycles. Conclusion: Tandem and high-resolution mass spectrometry analysis allowed rapid and accurate identification of the transformation products through the characteristic fragment ions and neutral loss. Rare ginsenosides with methoxyl groups grafted at the C-25 and C-20 positions were obtained for the first time by chemical transformation using the composite catalyst 12-HPW@MeSi, which also enabled cyclic heterogeneous transformation and facile centrifugal separation of ginsenosides. This work provides an efficient and recyclable strategy for the preparation of rare ginsenosides with the involvement of organic molecules.

• Food Science of Animal Resources
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• v.44 no.4
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• pp.873-884
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• 2024

Flunixin is a veterinary nonsteroidal anti-inflammatory agent whose residues have been investigated in their original form within tissues such as muscle and liver. However, flunixin remains in milk as a metabolite, and 5-hydroxy flunixin has been used as the primary marker for its surveillance. This study aimed to develop a quantitative method for detecting flunixin and 5-hydroxy flunixin in milk and to strengthen the monitoring system by applying to other livestock and fishery products. Two different methods were compared, and the target compounds were extracted from milk using an organic solvent, purified with C₁₈, concentrated, and reconstituted using a methanol-based solvent. Following filtering, the final sample was analyzed using liquid chromatography-tandem mass spectrometry. Method 1 is environmentally friendly due to the low use of reagents and is based on a multi-residue, multi-class analysis method approved by the Ministry of Food and Drug Safety. The accuracy and precision of both methods were 84.6%-115% and 0.7%-9.3%, respectively. Owing to the low matrix effect in milk and its convenience, Method 1 was evaluated for other matrices (beef, chicken, egg, flatfish, and shrimp) and its recovery and coefficient of variation are sufficient according to the Codex criteria (CAC/GL 71-2009). The limits of detection and quantification were 2-8 and 5-27 ㎍/kg for flunixin and 2-10 and 6-33 ㎍/kg for 5-hydroxy flunixin, respectively. This study can be used as a monitoring method for a positive list system that regulates veterinary drug residues for all livestock and fisheries products.

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.234.2-235
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• 2002

An efficient method for the simultaneous profiling analysis of organic acids and amino acids combined with a simple graphic pattern recognition method was developed for more objective diagnosis of organic acidurias and amino acidurias. In this method, extractive ethoxycarbonly (EOC) reaction of amino and sufhydry groups with ethyl chloroformate was followed by methodime (MO) formation of carbonyl group in aqueous solution (omitted)

• Journal of the Korean Society of Tobacco Science
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• v.8 no.2
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• pp.51-66
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• 1986

Volatile aroma components, non-volatile organic acids in lamina and stems of flue-cured(NC 2326) and burley ( Burley 21) were analyzed by gas chromatography and mass spectrometry, respectively. Then compositional differences of these components between lamina and stems were discussed. The contents of volatile components were higher in flue-cured than in burley tobacco, and it was also higher in lamina then in stem. The major aroma components in lamina were neophytadiene , nicotine, solanone and benzyl alcohol but those in stems were palmitic acid, neophytadiene, nicotine, solanone and phenyl ethyl acetate. On the other hand, the contents of non-volatile organic acids were higher in burley than in flue-cured tobacco, and these values of burley tobacco were higher in lamina than in stem but flue-cured tobacco were higher in stem than in lamina. The major acids in all the above four tabacco samples were malic, citric, oxalic and linolenic acid.

• Proceedings of the Membrane Society of Korea Conference
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• 1994.04a
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• pp.29-32
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• 1994

The increasing environmental risks exert strong demands for the knowledge of environmentally significant compounds and the reduction of such compounds on the earth. The risk reduction can, in principle, be most effectively achieved by minimizing the formation of environmental pollutants, by-products in many cases, during processes in factories, power plants and other sources. This can be done by on-line, real time monitoring the formation of pollutants at the moment when they are formed, and thereby through the feed-back control of the process.

• Journal of Korean Society for Atmospheric Environment
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• v.34 no.4
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• pp.625-625
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• 2018