• Journal of fish pathology
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• v.34 no.1
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• pp.71-80
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• 2021

Cephalexin, a semi-synthetic cephalosporin antibiotic, has long been used in fish aquaculture in various countries under legal authorization. The drug is thus widely available for use in other aquatic species except fishes like the crustacean whiteleg shrimp. This study aims to develop a sensitive method for laboratory residue studies to adopt in withdrawal period determinations. Through repeated trials from the existing methods developed for other food animal tissues, it was possible to achieve a sensitive high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method. The results showed that at a concentration of 0.1 mg/kg, the recovery rate was 81.79%, and C.V. value was 8.2%, which meet the recovery rate and C.V. recommended by Codex guideline. After satisfactory validation of analytical procedures, applicability to the shrimp tissue was confirmed in experimentally cephalexin-treated whiteleg shrimp. As a result, most muscle samples were detected below the limit of quantification (0.05 mg/kg) after day 3, and most hepatopancreas samples were detected below the limit of quantification after day 14. In particular, the limit of quantification 0.05 ppm with the presently developed method suggests sufficient sensitive over the current legal maximum residue limit of 0.2 mg/kg set for fishes.

• Journal of Pharmaceutical Investigation
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• v.41 no.2
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• pp.91-94
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• 2011

The purpose of this study was to investigate the effect of peptide charge on the interaction between peptide and poly(D,L-lactide-co-glycolide) (PLGA) for evaluating mechanism of acylated peptide formation in PLGA matrix. As a model peptide, octreotide, a synthetic somatostatin analogue and active ingredient of commercial PLGA product, was used. The disulfide group of octreotide was reduced with dithiothreitol and the sulfhydryl groups were modified with N-${\beta}$-maleimidopropionic acid (BMPA) to neutralize octreotide with positive charge in physiological conditions. The BMPA-conjugated octreotide was identified by measuring the molecular mass with liquid chromatography-mass spectrometry. In the interaction study with PLGA, native octreotide showed initial adsorption to PLGA and substantial production of acylated peptides (56% of overall peptide), whereas BMPA-conjugated octreotide showed minimal adsorption to PLGA and no acylation products for 42 days. Consequently, the neutralization of octreotide completely inhibited the peptide acylation by preventing interaction of peptide with PLGA. In conclusion, this study demonstrates that the initial polymer interaction of peptide is important step for peptide acylation in PLGA matrix and suggests the modulation of peptide charge as strategy for inhibiting the formation of acylated peptide impurities.

• Bulletin of the Korean Chemical Society
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• v.32 no.2
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• pp.524-530
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• 2011

In the present study, we demonstrate that SRM LC-MS/MS method developed by Luo et al. (ref. 10) can be successfully applied to the quantitative analysis of intracellular metabolites in E. coli that are collected at the exponential and stationary growth phases. A focus is given on measuring the changes in the concentrations of intracellular metabolites in batch cultures, which were induced during both the dynamically changing exponential and stationary growth phases. The following intracellular metabolites are quantified in the exponential and stationary phases of E. coli growth, using the SRM mode of a triple quadrupole mass spectrometer: glucose-1-phosphate, fructose-1,6-bisphosphate, phosphoenolpyruvate, pyruvate, acetyl-coenzyme A, 6-phosphogluconate, ribulose-5-phosphate, xylulose-5-phosphate, erythrose-4-phosphate. The determined intracellular metabolite concentration profiles are shown to be in a good agreement with the growth profiles of E. coli, which clearly indicates that SRM LC-MS/MS can be successfully used for following the metabolite changes induced at different growth stages.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.26 no.4
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• pp.396-403
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• 2016

Objectives: The study is to evaluate biological monitoring and risk assessment for epichlorohydrin-bisphenol A resin exposed from waterproofing or finishing work in the apartment building construction. Methods: Subjected workers were working on spray-painting and waterproofing work for 8 hours per day every 20 days. The urine samples were collected at the end of 20 days working period. For urinary bisphenol A as metabolite from epichlorohydrin-bisphenol A exposure, urine samples were analyzed with liquid chromatography mass-mass spectrometry(HPLC-MS/MS). Results: Geometric means of urinary bisphenol A(BPA) with no hydrolysis and with enzymic hydrolysis(BPA-EH) in the workers were $1.10{\mu}g/L$ and $2.90{\mu}g/L$. BPA-EH was 4 times higher than that of control group. The factors for working period and ages did not affect the variation of BPA and BPA-EH. The levels for BPA and BPA-EH were not higher than 95th percentile for exposure on human-life environment. Conclusions: The BPA and BPA-EH were therefore effective biological markers for epichlorohydrin-bisphenol A exposure workers, but not seem to hazardous exposure level. Waterproofing work in construction workshop is required to measuring work environment and health care management for the workers.

• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.158-164
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• 2014

Substance P and neuropeptide Y were discovered as early diagnostic biomarkers of acute myocardial infarction in Korean patients and confirmed using enzyme-linked immunosorbent assay (ELISA). We screened 12 peptides from the sera of Korean acute myocardial infarction (AMI) patients and detected 3 peptides (neuropeptide Y, substance P, and N-terminal pro-B-type natriuretic peptide) to be elevated from patients' sera by liquid chromatography mass/mass spectrometry. The elevated concentration of 3 peptides was confirmed by ELISA. The screening results revealed the substance P, neuropeptide Y, and pro-B-type natriuretic peptide (47-76) concentrations were higher in patients' sera than in healthy controls. The sensitivity and specificity of substance P for AMI diagnostic marker were 80% and 83%, respectively, and those of neuropeptide Y were 87% and 90%, respectively compared to healthy controls. These results suggest that substance P and neuropeptide Y could be used as early diagnostic biomarkers in patients with AMI.

• Food Science of Animal Resources
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• v.36 no.2
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• pp.254-261
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• 2016

The purpose of this study was to analyze oxidized methionines in the myosin isoforms of porcine longissimus thoracis, psoas major, and semimembranosus muscles by liquid chromatography (LC) and mass spectrometry (MS). A total of 836 queries matched to four myosin isoforms (myosin-1, -2, -4, and -7) were analyzed and each myosin isoform was identified by its unique peptides (7.3-13.3). Forty-four peptides were observed from all three muscles. Seventeen peptides were unique to the myosin isoform and the others were common peptides expressed in two or more myosin isoforms. Five were identified as oxidized peptides with one or two methionine sulfoxides with 16 amu of mass modification. Methionines on residues 215 (215), 438 (438), 853 (851), 856 (854), 1071 (1069), and 1106 (1104) of myosin-1 (myosin-4) were oxidized by the addition of oxygen. Myosin-2 had two oxidized methionines on residues 215 and 438. No queries matched to myosin-7 were observed as oxidized peptides. LC-MS/MS allows analysis of the oxidation of specific amino acids on specific residue sites, as well as in specific proteins in the food system.

• Journal of the Korean Chemical Society
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• v.68 no.3
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• pp.139-145
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• 2024

This study aims to elucidate the mechanism involved in the hydrolysis of the hexacyanoferrate(III) complex ion (Fe(CN)₆^3-) and the mechanism leading to the formation of Prussian blue (Fe^III₄[Fe_II(CN)₆]₃·xH₂O, PB) in acidic aqueous solutions at moderately elevated temperatures. Hydrolysis constitutes a crucial step in generating PB through the widely used single-source or precursor method. Recent PB syntheses predominantly rely on the single-source method, where hexacyanoferrate(II/III) is the exclusive reactant, as opposed to the co-precipitation method employing bare metal ions and hexacyanometalate ions. Despite the widespread adoption of the single-source method, mechanistic exploration remains largely unexplored and speculative. Utilizing UV-vis spectrophotometry, negative-ion mode liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS), and a devised reaction, this study identifies crucial intermediates, including aqueous Fe^2+/3+ ions and hydrocyanic acid (HCN) in the solution. These two intermediates eventually combine to form thermodynamically stable PB. The findings presented in this research significantly contribute to understanding the fundamental mechanism underlying the acid-catalyzed hydrolysis of the hexacyanoferrate(III) complex ion and the subsequent formation of PB, as proposed in the sequential mechanism introduced herein. This finding might contribute to the cost-effective synthesis of PB by incorporating diverse metal ions and potassium cyanide.

• Journal of Pharmaceutical Investigation
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• v.38 no.4
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• pp.269-275
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• 2008

The purpose of the present study was to evaluate the bioequivalence of two levofloxacin tablets, Jeil $Cravit^{TM}$ tablet (Jeil Pharm. Co., Ltd., Korea, reference drug) and $Lesacin^{TM}$ tablet (Ilhwa. Co., Ltd., Korea, test drug), according to the guidelines of Korea Food and Drug Administration (KFDA). Twenty-four healthy male Korean volunteers received two tablets containing levofloxacin 200 mg in a $2{\times}2$ crossover study. There was a one-week washout period between the doses. Plasma concentrations of levofloxacin were monitored for over a period of 24 hr after administration by using a high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). The area under the plasma concentration-time curve from time zero to 24 hr ($AUC_t$), maximum plasma drug concentration ($C_{max}$) and time to reach $C_{max}\;(T_{max})$ were complied from the plasma concentration-time data. Analysis of variance (ANOVA) test was utilized for the statistical analysis of the parameters using logarithmically transformed $AUC_t$ and $C_{max}$. The 90% confidence intervals of the $AUC_t$ ratio and the $C_{max}$ ratio for $Lesacin^{TM}$/Jeil $Cravit^{TM}$ were $\log\;0.9527{\sim}\log\;0.9981$ and $\log\;0.8712{\sim}\log\;1.0556$, respectively. These values were within the acceptable bioequivalence intervals of $\log\;0.80{\sim}\log\;1.25$, recommended by KFDA. In all of these results, we concluded that $Lesacin^{TM}$ tablet was bioequivalent to Jeil $Cravit^{TM}$ tablet, in terms of rate and extent of absorption.

• Korean Journal of Veterinary Service
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• v.38 no.2
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• pp.127-136
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• 2015

A simultaneous determination method was developed for nine preservatives (benzoic acid, sorbic acid, dehydroacetic acid, methyl-, ethyl-, isopropyl-, propyl-, isobutyl- and butyl-parabens) in sausage by liquid chromatography with electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS). Each parameter was established by multiple reaction monitoring in negative mode. Separation was achieved on a phenyl-hexyl ($2.5{\mu}m$, $2.1{\times}150mm$, Waters) with A-20 mM ammonium acetate containing 0.1% acetic acid in water, B-Acetonitrile as mobile phase with gradient mode at a flow rate of 0.3 mL/min. The developed method was validated for specificity, linearity, accuracy and precision in sausages samples. Linearity was over 0.998 with calibration curve of the mixed standards. The mean recoveries from sausages fortified at the level of 2.0~10.0 mg/L were in range of 98.60~109.16% with RSDs lower than 8.93%. The limits of detection (LOD) and the limits of quantification (LOQ) were in the range between 0.0003~0.085 mg/L and 0.01~0.257 mg/L, respectively. Intra-day precision and inter-day precision were 0.45~6.16% and 2.81~13.33%, respectively. Using presently developed determination method, 33 field sausage samples from Gwangju city in Korea were screened over nine preservatives. As a result, no preservatives were detected in all samples.

• Korean Journal of Clinical Laboratory Science
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• v.52 no.2
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• pp.91-97
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• 2020

Standardization of vitamin analysis continues around the world, and much effort has been made to improve the accuracy of the results. This study analyzed the sigma metrics of the vitamin D test using the external quality assessment (EQA) program. Sigma metrics is used for quantitative tests performed in the laboratory, and the test results can be objectively visualized in terms of quality. This analysis was performed based on the accuracy of the College of American Pathologists (CAP) using the results of the 2019 accuracy-based vitamin D (ABVD) survey, and about 300 laboratories participated in the survey. Reference values were obtained by the Center for Disease Control and Prevention (CDC) reference laboratory. At six different concentrations, the sigma metrics were analyzed to be 1.00, 1.85, 2.42, 1.01, 1.54 and 0.78, respectively. An average of 1.43 sigma metrics was determined. In particular, only positive biases for ABVD-16 and 17 were shown in the liquid chromatography tandem-mass spectrometry (LC-MS/MS), which is the standard method for vitamin D determination when compared to the reference values. The causes of the difference can be explained by cross reactivity to various vitamin D metabolites. Laboratories need to improve their overall performance.