• Bulletin of the Korean Chemical Society
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• v.15 no.12
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• pp.1038-1042
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• 1994

The amperometric responses of thiourea were studied in 0.1 M NaOH by flow injection analysis. D. C. amperometric and pulsed amperometric detection methods were applied for the determination of thiourea at novel metal electrodes such as Pt and Au. Triple-step potential waveforms were adopted in the pulsed amperometric detection. With an optimized pulsed waveform, the current for the oxidation of thiourea was examined with the variation of flow rate of carrier solution and with the change in the amount of sample injected. Gold working electrode turned out to be better in sensitivity and signal to noise ratio than Pt electrode in the pulsed amperometric detection of thiourea. Detection limit is estimated to be 5.33 ${\times}$ 10$^{-5}$ M with this detection method.

• The Korea Journal of Herbology
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• v.23 no.4
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• pp.171-177
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• 2008

Objectives: This study presents a reversed-phase high-performance liquid chromatography- pulsed amperometric detection(RP-HPLC-PAD) method for the determination of puerarin and daidzin in Puerariae Radix extract and Chinese medicinal preparations. Methods: Chromatographic separation was performed using a 10% acetonitrile with a reversed-phase column(Unison UK-C18, $100mm{\times}2.0mm$ I.D.; $3{\mu}m$). The analyses were detected by pulsed amperometric detector(PAD) in alkaline conditions by combining with post-column NaOH solution. Geniposide was used as an internal standard. Results: The limit of detection(S/N=3) and the limit of quantification(S/N=10) were 0.025 ng, 0.075 ng for puerarin, and 0.05 ng, 0.15 ng for daidzin, respectively. The intra- and inter-day precisions(RSDs) were less than 6.5% and average recoveries of puerarin were 99.7-101.3% and those of daidzin were 101.0-102.8%. Conclusions: According to above results, we developed a determination method for puerarin and daidzin in Puerariae Radix with high sensitivity and selectivitely.

• Bulletin of the Korean Chemical Society
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• v.18 no.3
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• pp.316-318
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• 1997

A general and universal detection method, which can be used in high performance liquid chromatography (HPLC) and flow injection analysis (FIA) system for the determination of any metal ions complexing with ethylenediaminetetraacetic acid (EDTA), is demonstrated. Pulsed amperometric detection scheme is applied in a flow-through thin layer electrochemical cell at an Au working electrode. Fluctuation of peak current level at the same flow rate of carrier solution is minimized at this solid working electrode, whereas not at a dropping mercury electrode. Removal of dissolved oxygen can be omitted with this detection method, which is a required step for cathodic detection methods. Also, a group of metal ions can be determined selectively and indirectly with this detection scheme.

• Bulletin of the Korean Chemical Society
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• v.17 no.2
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• pp.143-146
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• 1996

A continuous potential pulse is applied to a silver-working electrode on a pulsed amperometric detector (PAD) for detection of free cyanide and sulfide. The moving phase is 0.1 M sodium hydroxide, 0.5 M sodium acetate and 5% (v/v) ethylenediamine mixture, and the flow rate is 0.7 mL/min. Optimized pulse conditions include a -200 mV (vs. Ag/AgCl reference electrode) detection potential(Ed) for 60 msec and 50 mV cleaning potential (Ec) for 120 msec. The silver working electrode surface is not poisoned by cyanide or sulfide, and the PAD maintains long-term stability without loss of sensitivity and reproducibility at these pulse conditions. The detection limit of cyanide and sulfide separated by ion chromatography using an anion exchange column is 0.1 ppm and 0.05 ppm, respectively.

• 대한한약학회:학술대회논문집
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• 2007.11a
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• pp.175-175
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• 2007

• Journal of Ginseng Research
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• v.44 no.4
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• pp.563-569
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• 2020

Background: White ginseng consists of the roots and rhizomes of the Panax species, and red ginseng is made by steaming and drying white ginseng. While red ginseng has both polar and nonpolar ginsenosides, previous studies showed white ginseng to have only polar ginsenosides. Because nonpolar ginsenosides are formed through the manufacture of red ginseng from white ginseng, researchers have generally thought that nonpolar ginsenosides do not exist in white ginseng. Methods: We developed a simultaneous quantitative method for six nonpolar ginsenosides in white ginseng using reverse-phase high-performance liquid chromatography coupled with integrated pulsed amperometric detection. The nonpolar ginsenosides of white ginseng were extracted for 4 h under reflux with 50% methanol. Results: Using the gradient elution system, all target components were completely separated within 50 min. Nonpolar ginsenosides were determined in the rhizome head (RH), main root (MR), lateral root, and hairy root (HR) of 6-year-old white ginseng samples obtained from several regions (Geumsan, Punggi, and Kanghwa). The total content in the HR of white ginseng was 37.8-56.8% of that in the HR of red ginseng. The total content in the MR of white ginseng was 5.9-24.3% of that in the MR of red ginseng. In addition, the total content in the RH of white ginseng was 28.5-35.8% of that in the HR of red ginseng Conclusion: It was confirmed that nonpolar ginsenosides known to be specific components of red ginseng were present at substantial concentrations in the HR or RH of white ginseng.

• 대한한약학회:학술대회논문집
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• 2007.11a
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• pp.182-182
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• 2007

• YAKHAK HOEJI
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• v.53 no.1
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• pp.34-40
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• 2009

The glycosylation of therapeutic glycoproteins can affect their efficacy, stability, solubility, and half-life. Analyzing the composition of monosaccharides, such as that of neutral and amino sugars, is the first step for elucidating the structure of glycan attached to glycoproteins. In the present study, neutral and amino sugars of lectin obtained from Maackia fauriei were analyzed using an enzyme-linked lectinsorbent assay (ELLA) and high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Peroxidase-labeled lectins such as concanavalin A, Ricinus communis agglutinin, and soybean agglutinin were used for ELLA, since they specifically bind to the monosaccharide residue most frequently encountered in a glycan. The hydrosylate of lectin was prepared by treatment with trifluoroacetic acid, which resulted in the lectin mainly possessing the N-glycan consisting of 98.1 pmol Fuc, 342.1 pmol GlcN, 51.9 pmol Gal, 678.9 pmol Man, and 330.7 pmol Xyl. The present results demonstrate that ELLA and HPAEC-PAD are very effective methods for rapidly estimating the types and relative amounts of monosaccharides in intact glycoproteins.

• YAKHAK HOEJI
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• v.57 no.6
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• pp.406-411
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• 2013

Rumex crispus (Curled Dock, Polygonaceae) is a perennial wild plant used in traditional medicine as a laxative, astringent, and to treat blood and skin disease. The ethanol extract of R. crispus was obtained and its carbohydrate contents were analyzed using high-performance anion-exchange chromatography with pulsed amperometric detection. The anabolic effects of R. crispus in human osteoblastic MG-63 cells were investigated using the WST-8 assay, alkalinephosphatase (ALP) assay, and mineralization assay. The ethanol extract increased the proliferation of MG-63 cells and stimulated ALP activity in a dose-dependent manner over a 72-hrs period. Additionally, the ethanol extract dose-dependently stimulated the formation of bone nodules in MG-63 cells treated for 12 days. The ethyl acetate fraction from the ethanol extract did not affect osteoblast viability but induced an increase in ALP activity. In conclusion, the ethanol extract of R. crispus increases the proliferation and bone-forming activity of osteoblasts, and hence it could be used in the development of bone-forming stimulatory nutraceuticals and osteoporosis-related medicines.

• KSBB Journal
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• v.14 no.3
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• pp.384-388
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• 1999

We have used high pH anion-exchange chromatography to analyze low level (below $20{\mu}M$) $\alpha$-D-glucose-1-phosphate (G-1-P) that can be used as a cytostatic compound, an antibiotic, and immunosuppressive drug. Our chromatographic method afforded excellent peak resolution and seletivity for glucose-6-phosphate and various maltooligosaccharides as well as G-1-P. The pulsed amperometric detector yielded linear response on G-1-P ranging from 2 - $20{\mu}M$, giving slope of $4.8{\times}10^4$(peak area/${\mu}M$). The detection limit was $2{\mu}M$. This method was applied to the purification of thermophilic $\alpha$-glucan phosphorylase from Thermus caldophilus. The technique will be extremely useful in future studies concerning carbohydrate metabolism in living organisms.