• Mass Spectrometry Letters
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• v.2 no.2
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• pp.37-40
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• 2011

Saccharin is a commonly used artificial sweetener in foodstuffs. However, for its carcinogenic dispute, it has been regulated by government bodies. In this study, isotope dilution mass spectrometry (ID-MS) was introduced for the accurate quantification of saccharin. To employ ID-LC/MS, we obtained its isotope analogue, $^{13}C_1$-sodium saccharin, by customized synthesis. Samples were spiked with $^{13}C_1$-sodium saccharin and analyzed with LC/MS in negative mode. Chromatographic conditions were optimized for the adequate chromatographic retention and separation of saccharin with a $C_{18}$ column. MS was operated with electrospray ionization by the selected ion monitoring (SIM) mode of $[M-H]^-$ for saccharin (m/z 182) and $[M-Na]^-$ for its isotope analogue (m/z 183). To validate the ID-LC/MS method for accurate measurement, we prepared a batch of a candidate material by sortifying quasi-tea-drinks with saccharin and analyzed samples gravimetrically fortified in various levels of concentration. The repeatability and reproducibility of this method was tested by analyzing the reference material. Result show that ID-LC/MS is a reliable method for the quantitative analysis of saccharin.

• Analytical Science and Technology
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• v.30 no.2
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• pp.102-111
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• 2017

Here we reported a methodology for identification of triacylglycerols (TAGs) and diacylglycerols (DAGs) in coix seed by preparative thin layer chromatography (prep-TLC) and non-aqueous reversed-phase liquid chromatography (NARP LC)-atmospheric pressure chemical ionization (APCI) tandem mass spectrometry (MS/MS). Lipid components were extracted from coix seed by reflux extraction using n-hexane for 3 hr. TAGs and DAGs in coix seed extract were effectively purified and isolated from matrix interferences by prep-TLC and then analyzed by LC-APCI-MS and MS/MS for identification. TAGs were effectively identified taking into consideration of their LC retention behavior, APCI-MS spectra patterns, and MS/MS spectra of $[DAG]^+$ ions. In MS/MS spectra of TAGs, diacylglycerol-like fragment $[DAG]^+$ ions were useful to identify TAGs with isobaric fragment ions. Based on an established method, 27 TAGs and 8 DAGs were identified in coix seed extract. Among them, 15 TAGs and 8 DAGs were for the first time observed in coix seed. Interestingly, some of TAGs isolated by prep-TLC were partly converted into DAGs through probably photolysis process during storing in room temperature. Thus, degradation phenomenon of TAGs should be considered in the quality evaluation and nutritional property of coix seed. LC-APCI-MS/MS combined with prep-TLC will be practical method for precise TAG and DAG analysis of other herbal plants.

• Journal of Microbiology and Biotechnology
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• v.20 no.4
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• pp.809-816
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• 2010

Microbial biotransformations can be used to predict mammalian drug metabolism. The present investigation deals with microbial biotransformation of valdecoxib using microbial cultures. Thirty-nine bacterial, fungal, and yeast cultures were used to elucidate the biotransformation pathway of valdecoxib. A number of microorganisms metabolized valdecoxib to various levels to yield nine metabolites, which were identified by HPLC-DAD and LC-MS-MS analyses. HPLC analysis of biotransformed products indicated that a majority of the metabolites are more polar than the substrate valdecoxib. Basing on LC-MS-MS analysis, the major metabolite was identified as a hydroxymethyl metabolite of valdecoxib, whereas the remaining metabolites were produced by carboxylation, demethylation, ring hydroxylation, N-acetylation, or a combination of these reactions. The hydroxymethyl and carboxylic acid metabolites were known to be produced in metabolism by mammals. From the results, it can be concluded that microbial cultures, particularly fungi, can be used to predict mammalian drug metabolism.

• Natural Product Sciences
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• v.27 no.4
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• pp.257-263
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• 2021

Aster species (Asteraceae) are widely distributed edible and medicinal plants, known to contain various specialized metabolites including polyphenols and saponins. However, systemic analysis on the chemical profiles of these plants have rarely been made. Here we analyzed the phytochemical constituents in leaves of 6 Aster species occurring in Korea, A. ageratoides, A. altaicus var. uchiyamae, A. glehnii, A. hispidus, A. incisus, and A. yomena, by applying a LC-MS/MS-based untargeted metabolomics approach. The analysis revealed that A. ageratoides, A. hispidus, and A. yomena are relatively rich in saponins most of which are expected to be previously unknown.

• Polymer Science and Technology
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• v.22 no.2
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• pp.188-193
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• 2011

• Journal of Korean Neurosurgical Society
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• v.42 no.6
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• pp.470-474
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• 2007

Objective : The brain is dependent on glucose as an energy source. Intricate homeostatic mechanisms have been implicated in maintaining the blood glucose concentration in the brain. The aim of this study is to find the way to identify the metabolic proteins regulating the glucose in rat hypothalamus. Methods : In this study, we analysed the secretome from rat hypothalamus in vivo. We introduced 500 nM of insulin into the rat hypothalamus. The chromatographic patterns of the secretome were identified, after which Mass Spectrometry-Mass Spectrometry (MS-MS) analysis was performed. Results : In Liquid Chromatography-Mass Spectrometry (LC-MS) analysis, 60 proteins were identified in the secretome. Among them, 8 novel proteins were unveiled and were associated with the energy metabolism of insulin signaling in mitochondria of rat hypothalamic neuron. Nineteen other proteins have unknown functions. These ligands were confirmed to be secreting from the rat hypothalmus on insulin signaling by western blotting. Conclusion : The hypothalamus is the master endocrine gland responsible for the regulation of various physiological and metabolic processes. Proteomics using LC-MS analysis offer a efficient means for generating a comprehensive analysis of hypothalamic protein expression by insulin signaling.

• Journal of Korean Society on Water Environment
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• v.25 no.5
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• pp.720-726
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• 2009

We investigated the most effective pre-treatment processes and LC/MS/MS condition for microcystins analysis. With a step-by-step pre-treatment, efficiencies of several established methods were compared. At the level of cell burst, sonication method was found to be the most efficient. As a mycrocystins first extraction solvent, 5% acetic acid showed the highest efficiency. An isolation and recovery rate of mycrocystins of ODS Sep-Pak $C_{18}$ cartridge was higher than HLB SPE cartridge. As a final elution solvent from cartridge, 100% MeOH had a better efficiency than others. Using a LC/MS/MS, effective analytical methods were established. C18 reverse column was used and gradient elution was performed with using acetonitrile, 0.1% formic acid as a mobile phase. We analysed to 0.8 mL/min flow rate fit to the $5{\mu}m$ particle size column and $55^{\circ}C$ housing temperature. The validity of established analytical method was evaluated that MDL as average $0.050{\pm}0.014{\mu}g/L$ and LOQ as average $0.160{\pm}0.045{\mu}g/L$ had a good sensitivity over 40 magnification rather than $2{\mu}g/L$ detection limit of HPLC.

• Journal of the Korean Chemical Society
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• v.55 no.4
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• pp.626-632
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• 2011

Phoxim, which is one of veterinary drugs, is a well-known antiparasitic agent in wide use. In this paper, phoxim was extracted from cattle and pig tissue using solid-phase extraction (SPE) employing a silica cartridge with acetonitrile. Liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) for the analysis of phoxim from animal tissue was presented. Phoxim was detected on a $C_{18}$ column ($2.1{\times}100\;mm$, $3.5\;{\mu}m$) using a mobile phase of 0.1% formic acid in water and acetonitrile. A linear correlation observed in the calibration curves for cattle (0.0048~2.0 mg/kg) and pig (0.0055~2.0 mg/kg) showed above $r^2$=0.995. Accuracy measured at concentrations ranging from 0.0048 to 0.2 mg/kg was the range of 68.2~106.9%. Limit of detection (LOD) and limit of quantitation (LOQ) were the range of 0.0014~0.0017 mg/kg and 0.0048~0.0055 mg/kg, respectively. The precision (RSD%) was below 11.2%.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.4
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• pp.404-410
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• 2021

Although, mouse bioassay for the monitoring of azaspiracids (AZAs) toxins in shellfish has been used previously, the reported method has low sensitivity and it is time-consuming. Recently, there is an interest in the quantitative analysis of AZAs using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The purpose of this study is to verify the simultaneous analysis of AZAs in shellfish and tunicate in Korea using LC-MS/MS. To validate the method, linearity, limit of detection (LOD), limit of quantification (LOQ), precision, accuracy, and repeatability were determined. All standard compounds were analyzed within 7 min. The correlation coefficients (R²) of the standard solution was higher than 0.9995 (within the range of 0.8-10.0 ㎍/L). The LODs and LOQs of AZAs in shellfish were 0.08-0.16 ㎍/kg and 0.23-0.50 ㎍/kg, respectively. The accuracy and precision of the method for determining AZAs in shellfish were 87.1-93.0% and 1.23-4.91%, respectively. Consequently, the verified LC-MS/MS method is suitable to analyze AZAs in shellfish and tunicates in Korea.

• Mass Spectrometry Letters
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• v.13 no.3
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• pp.58-83
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• 2022

We developed analytical methods using high performance chromatography (HPLC) and liquid chromatography tandem mass spectrometry (LC-MS/MS) for the simultaneous determination of 80 unapproved compounds in dietary supplements. The target compounds for analysis were unapproved ingredients (e.g., pharmaceuticals) that have potential adverse effects on consumers owing to accidental misuse, overuse, and interaction with other medication in dietary supplement. Two analytical methods were tested to identify the optimal validation results according to AOAC guideline. As a result, limit of quantification (LOQ) was 0.14-0.5 ㎍ mL^-1; linearity (r²) was ≥ 0.99; accuracy (expressed as recovery) was 78.9-114%; precision (relative standard deviation) was ≤ 4.28% in the HPLC method. In the LC-MS/MS method, LOQ was 0.01-2 ng mL^-1, linearity (r²) was ≥0.98, accuracy was 71.7-119%; precision was ≤ 12.5%. The developed methods were applied to 51 dietary supplements collected from 2019 to 2021 through MFDS alert system. Based on our previous monitoring study, major compounds were icariin, sibutramine, yohimbine, sildenafil, tadalafil, sennosides (A, B), cascarosides (A, B, C, D), and phenolphthalein. In this study, we re-analyzed samples of detected compounds, and evaluated the statistical difference using Bland-Altman analysis to compare two analytical approaches between HPLC and LC-MS/MS. These results showed a good agreement between two methods that can be used to monitor the unapproved ingredients in dietary supplements. The developed two methods are complementarily suitable for monitoring the adulteration of 80 unapproved compounds in dietary supplements.