• Korean Journal of Food Science and Technology
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• v.51 no.5
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• pp.420-424
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• 2019

An HPLC analysis method was developed and standardized for the detection of dieckol as a functional food ingredient in Ecklonia cava extracts. HPLC was performed using a Capcell Pak C18 column ($250{\times}4.6mm$, $5{\mu}m$) with a gradient elution of water and acetonitrile, both containing 0.1% (v/v) trifluoroacetic acid, at a flow rate of 1.0 mL/min at $25^{\circ}C$. The eluate was detected at 230 nm. For validation, the specificity, linearity, accuracy, precision, limit of detection (LOD), and limit of quantification (LOQ) of dieckol were measured. The calibration curve for the detection of dieckol had high linearity ($R^2=0.9994$), with LOD and LOQ values of 0.38 and $1.16{\mu}g/mL$, respectively. Recovery of the quantified compound ranged from 99.61 to 100.71%. The relative standard deviation values of the intra-day and inter-day precisions were less than 1.7 and 1.25%, respectively. These results indicate that the reported HPLC method is simple, reliable, and reproducible for the detection of dieckol in Ecklonia cava extracts.

• Journal of Korean Society for Atmospheric Environment
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• v.7 no.2
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• pp.137-142
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• 1991

A method is developed for the simultaneous determination of dissolved iron, copper, and zinc in rainwater. The method involves 25-fold evaporative concentration, ion chromatographic separation and subsequent spectrophotometric detection after post-column reaction with 4-(2-pyridylazo) resorcinol. Analytical sensitivities, being defined by the slopes of calibration curves, are 0.93, 0.54, and 0.11 Abs/ $\mu$g/ml for iron, copper, zinc, respectively. Detection limits render around a few tenth of one ng/ml. Precisions evaluated by replicate analysis of real sample are better than 10% RSD. Due to the lack of certified standards for rainwater, the accuracy of the method could not be assessed directly. However, the results of this method agree well with those by inductively coupled plasma mass spectrometry. Analytical results for a suite of Seoul rainwaters are presented herein.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.9
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• pp.1375-1380
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• 1989

Mobility reduction parameters are extracted using a method based on the exploitatiion of Id-Vg and Gm-Vg characteristics of short channel n-MOSFETs in strong inversion region at room temperature. It is found that the reduction of the maximum field effect mobility, \ulcornerFE,max, with the channel length is due to i) the difference between the threshold voltage and the gate voltage which corresponds to the maximum transconductance, and ii) the channel length dependence of the mobility attenuation coefficient, \ulcorner The low field mobility, \ulcorner, is found to be independent of the channel length down to 0.25 \ulcorner ofeffective channel length. Also, the channel length reduction, -I, the mobility attenuation coefficient, \ulcorner the threshold voltage, Vt, and the source-drain resistance, Rsd, are determined from the Id-Vg and -gm-Vg characteristics n-MOSFETs.

• Applied Chemistry
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• v.16 no.1
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• pp.25-28
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• 2012

A determination method of cyanide ion (CN^-) using nickel complexation reaction by continuous monitoring system. The mechanical parameters and chemical conditions of the complexation reaction were investigated prior to application of continuous monitoring system for determination of cyanide. On the optimized conditions, the calibration curve was linear over the range from 5.0×10^-6 to 1.0×10^-4 M. In this range, 2.40% of the reproducibility (RSD, n=3) was obtained. The limit of detection (3σ/s) was calculated to be 1.8×10^-6 M.

• Journal of the Korean Chemical Society
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• v.31 no.5
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• pp.425-433
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• 1987

The separation of 19 organochlorine pesticides was studied by capillary column gas chromatography. The applicability of this method to the fresh rice was investigated. Comparison of the resolution of pesticides by OV-17 and SE-30 capillary columns revealed that OV-17 column (25m ${\times}$ 0.20mm, 0.27${\mu}$m thickness) showed better resolution. The relative standard deviations (RSD) for their retention times and peak areas obtained by splitless injection mode were within 0.16% and 8.2%, respectively. The recoveries of pesticides spiked in fresh rice were mostly over 85% and their RSDS did not exceed 11.4%.

• Natural Product Sciences
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• v.25 no.2
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• pp.111-114
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• 2019

The herbal formula, DF-02, consisting of Ephedra intermedia and Rheum palmatum are used for the treatment of the metabolic diseases such as obesity and liver fibrosis in Korean local clinics. We aimed to develop the simultaneous analytical conditions for four standards, (+)-pseudoephedrine (PSEP) and (-)-ephedrine (EP) for E. intermedia, and aloe-emodin (AE) and chrysophanol (CP) for R. palmatum using HPLC-UV techniques. The validated conditions yielded the high precision (relative standard deviation (RSD) < 3.65%) and the recoveries (94 - 106%) using the calibration curves with high linearity ($R^2$ > 0.9994). As a result, four standards of DF-02 were simultaneously determined under the developed method, which will be utilized for the quality control or evaluation of DF-02 and many herbal preparations containing E. intermedia and R. palmatum.

• Analytical Science and Technology
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• v.25 no.6
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• pp.460-466
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• 2012

An environmentally friendly, so-called green, high performance liquid chromatography method was developed and validated for the determination of trans, trans-muconic acid (t,t-MA) in human urine as a biomarker of benzene exposure. After urinary t,t-MA was extracted and enriched using solid-phase extraction, a MF-Ph1 SG80 ($150mm{\times}2.0mm$ I.D., 5 ${\mu}m$) column with a mobile phase of 10 mM $KH_2PO_4$ containing 0.1% $H_3PO_4$ was used for isocratic separation of t,t-MA with UV detection at 259 nm. The calibration curve was constructed in the range of 0.1-5.0 mg/L with good linearity ($r^2$=0.9992). The intra-day and inter-day precision (as RSD) were 0.9-8.5% and 3.1-4.5%, respectively. The average recovery ranged from 97.5% to 101.7%. The green sample preparation and separation with no organic solvents were successfully achieved. The validated method would be suitable for the routine biological monitoring of benzene exposure in the occupational settings.

• Analytical Science and Technology
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• v.11 no.5
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• pp.353-359
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• 1998

Danazol, one of the IOC banned substances, is a synthetic steroid which stimulates the synthesis of cellular protein with multiple and diverse biologic effects. To confirm the androgenic effects of danazol, levels of eight endogenous steroids and its major metabolite in human urine were simultaneously analyzed by selected ion monitoring (SIM) of GC/MS after oral administration. The recovery range of this method was 71.59%~93.56% and the RSD values of precision and accuracy test were 1.87%~10.48% and 1.32%~11.25%, respectively. The limits of detection of most of the drugs were $0.01{\sim}0.05{\mu}g/mL$ and calibration was carried out using urine spiked with each endogenous steroid and ethisterone standard at a concentration of 0.1, 0.5, 1.0, 10, 20 and $50{\mu}g/mL$ and with $10{\mu}g/mL$ of internal standard. Correlation coefficients varied between 0.963 and 0.991. The endogenous steroid profiling is one of valuatle tool for decteation of anabolic steroids.

• Asian-Australasian Journal of Animal Sciences
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• v.27 no.6
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• pp.871-879
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• 2014

Two experiments were conducted to determine the digestible energy (DE) and metabolizable energy (ME) contents of corn gluten feed (CGF) for finishing pigs and to develop equations predicting the DE and ME content from the chemical composition of the CGF samples, as well as validate the accuracy of the prediction equations. In Exp. 1, ten CGF samples from seven provinces of China were collected and fed to 66 finishing barrows (Duroc${\times}$Landrace${\times}$Yorkshire) with an initial body weight (BW) of $51.9{\pm}5.5$ kg. The pigs were assigned to 11 diets comprising one basal diet and 10 CGF test diets with six pigs fed each diet. The basal diet contained corn (76%), dehulled soybean meal (21%) and premix (3%). The ten test diets were formulated by substituting 25% of the corn and dehulled soybean meal with CGF and contained corn (57%), dehulled soybean meal (15.75%), CGF (24.25%) and premix (3%). In Exp. 2, two additional CGF sources were collected as validation samples to test the accuracy of the prediction equations. In this experiment, 18 barrows (Duroc${\times}$Landrace${\times}$Yorkshire) with an initial BW of $61.1{\pm}4.0$ kg were randomly allotted to be fed either the basal diet or two CGF containing diets which had a similar composition as used in Exp. 1. The DE and ME of CGF ranged from 10.37 to 12.85 MJ/kg of dry matter (DM) and 9.53 to 12.49 MJ/kg of DM, respectively. Through stepwise regression analysis, several prediction equations of DE and ME were generated. The best fit equations were: DE, MJ/kg of DM = 18.30-0.13 neutral detergent fiber-0.22 ether extract, with $R^2$ = 0.95, residual standard deviation (RSD) = 0.21 and p<0.01; and ME, MJ/kg of DM = 12.82+0.11 Starch-0.26 acid detergent fiber, with $R^2$ = 0.94, RSD = 0.20 and p<0.01. These results indicate that the DE and ME content of CGF varied substantially but the DE and ME for finishing pigs can be accurately predicted from equations based on nutritional analysis.

• Journal of Food Hygiene and Safety
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• v.27 no.1
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• pp.37-41
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• 2012

The current standard for testing tetrodotoxin (TTX) in foodstuffs is the mouse bioassay (MBA) in Korea as in many other countries. However, this test suffers from potential ethical concerns over the use of live animals. In addition, the mouse bioassay does not test for a specific toxin thus a sample resulting in mouse incapacitation would need further confirmatory testing to determine the exact source toxin (e.g., TTX, STX, brevotoxin, etc.). Furthermore, though the time of death is proportional to toxicity in this assay, the dynamic range for this proportional relationship is small thus many samples must be diluted and new mice be injected to yield a result that falls within the quantitative dynamic range. Therefore, in recent years, there have been many efforts in this field to develop alternative assays. High performance liquid chromatography (HPLC) coupled with mass spectrometry (MS) has been emerged as one of the most promising options. A LC-MS-MS method involves solid-phase extraction (SPE) and followed by analysis using an electrospray in the positive ionization mode and multiple reactions monitoring (MRM). To adopt LC-MS-MS method as alternative standard for testing TTX, we performed a validation study for the quantification of TTX in puffer fish. This LC-MS-MS method showed good sensitivity as limits of detection (LOD) of $0.03{\sim}0.08{\mu}g/g$ and limits of quantification (LOQ) of $0.10{\sim}0.25{\mu}g/g$. The linearity ($r^2$) of tetrodotoxin were 0.9986~0.9997, the recovery were 80.9~103.0% and the relative standard deviations (RSD) were 4.3~13.0%. The correlation coefficient between the mouse bioassay and LC/MS/MS method was higher than 0.95.