• Korean Journal of Veterinary Service
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• v.29 no.3
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• pp.339-346
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• 2006

Semi-micro-HPLC using a column-switching technique was developed for simultaneous determination of vitamin A and E contents in infant formula. Vitamin A and E were extracted by PDA - HPLC with reversed phase column using organic solvent and their contents in Certified Reference Material (CRM) and infant formula were determined and compared with hydrolysis method and rapid extraction. Developed method has many advantages of simple and rapid sample preparation and simultaneous determination of vitamin A and E by micro-HPLC using reversed phase column.

• Bulletin of the Korean Chemical Society
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• v.22 no.6
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• pp.565-569
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• 2001

The spectral correction matrix has been established to study the simultaneous complextions between metals and a ligand, and it eliminated the mutual influence among the complexes. The two sensitive reations between iron(Ⅱ) and 1-(6-bromo-2-benzothiazolylazo)-2-naphthol(BBTAN) and zinc (Ⅱ) and BBTAN have been investigated and applied to the simultaneous determination of Zn and Fe at pH 8.5 in the presence of triton x-100. This method gave the simples determination of the characteristic constants of the complexes. For the analysis of natural water, foods and other samoles, the recoveries of Fe and Zn were between 92 and 109% and between 91 and 104%, and their relative standard deviations were less than 5.5 and 11%, respectively.

• Bulletin of the Korean Chemical Society
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• v.27 no.6
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• pp.863-868
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• 2006

The partial least squares (PLS-1) calibration model based on spectrophotometric measurement, for the simultaneous determination of sulfite and sulfide is described. This method is based on the difference between the rate of the reaction of sulfide and sulfite with Malachite Green in pH 7.0 buffer solution and at 25 ${^{\circ}C}$. The absorption kinetic profiles of the solutions were monitored by measuring the decrease in the absorbance of Malachite Green at 617 nm in the time range 10-180 s after initiation of the reactions with 2 s intervals. The experimental calibration matrix for partial least squares (PLS-1) calibration was designed with 24 samples. The cross-validation method was used for selecting the number of factors. The results showed that simultaneous determination could be performed in the range 0.030-1.5 and 0.030-1.2 $\mu$g m$L ^{-1}$ for sulfite and sulfide, respectively. The proposed method was successfully applied to simultaneous determination of sulfite and sulfide in water samples and whole human blood.

• Bulletin of the Korean Chemical Society
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• v.24 no.9
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• pp.1324-1328
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• 2003

The simultaneous determination of anions ($SO_4 ^{2-},\;Cl^-,\;and\;NO_3^-$) and cations ($Na^+,\;NH^{4+},\;K^+,\;Mg^{2+},\;and\;Ca^{2+}$) in natural water obtained by Nakdong River waters system in Korea were performed by ion-exclusion/cationexchange chromatography with conductimetric detection. The stationary phase was a polymethacrylate-based weakly acidic cation-exchange resin column in the $H^+$-form and a weak-acid eluent. When using only a 1.4 mM sulfosalicylic acid/6 mM 18-crown-6 ether as an eluent, good resolution of both anions and cations, minimum time required for the separation, and satisfactory detection sensitivity were obtained in a reasonable time. The method was successfully applied to the simultaneous determination of anions and cations in natural waters.

• Archives of Pharmacal Research
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• v.9 no.4
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• pp.211-214
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• 1986

A simultaneous determination method of alkaline earth metals was attempted with the conventional high performance liquid chromatographic system. Four cations, namely, magnesium, calcium, strontium and barium ion, were injected directly as aqueous solution into an eluent containing copper chloride solution and and were successfully separated and determined on a separating column (Zipax SCX, 4.6 mm i.d. ${\times}25$ cm length, Du Pont, USA) by using a variable wavelength UV detector. The linear calibration curves were obtianed in the range from $1.0{\times}10^{-4}M$ to $5.0{\times}10^{-4}M$ and the correlation coefficient of the calibration curve for each metal of magnesium and calcium in tap water. Alkaline earth metals were determined with the conventional high performance liquid chromatographic system.

• Journal of Environmental Health Sciences
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• v.21 no.3
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• pp.87-95
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• 1995

A rapid and selective co-extraction systems of copper and zinc-thiocyanate complex into various types of alkylamine for the simultaneous determination of two metal ions by atomic absorption spectrometry and ion chromatograph have been proposed. The quantitative extractions of Cu(II) and Zn(II) at 0.1 M-thiocyanate and 0.1 M-HCI were achieved with Aliquat 336-$CHCl_3$. The detection limits of Cu and Zn were 2 ppb and 0.9 ppb respectively.

• Herbal Formula Science
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• v.18 no.2
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• pp.251-257
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• 2010

Objectives : To develop and validate High-performance liquid chromatography-photodiode array methods for simultaneous determination of two constituents in Oryeong-san(ORS). Methods : Reverse-phase chromatography using a Gemini C18 column operating at $40^{\circ}C$, and photodiode array(PDA) detection at 280 nm, were used for quantification of the two marker components of ORS. The mobile phase using a gradient flow consisted of two solvent systems. Solvent A was $H_2O$ and solvent B was acetonitrile. Results : Calibration curves were acquired with correlation coefficient ($r^2$)>0.9999, and the relative standard deviation(RSD) values(%) for intra- and inter-day precision were not exceed 1.0%. The recovery rate of each compound was in the range of 93.01-104.16%, with an RSD less than 2.0%. The contents of two compounds in ORS were 1.10-3.72 mg/g. Conclusions : The established HPLC method will be helpful to improve quality control of ORS.

• Bulletin of the Korean Chemical Society
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• v.25 no.12
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• pp.1764-1768
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• 2004

The present work reports on the investigations based on the interaction of sodium hydroxide with catechol derivatives. The first derivative spectra allowed the simultaneous determination of levodopa and carbidopa. The calibration graph was constructed from the first derivative signals by measuring $^1D$ at 350 nm for standard samples containing between 3 and 30 mg $L^{-1}$ of levodopa and at 305 nm for standard samples containing between 3 and 80 mg $L^{-1}$ of carbidopa. This method offers the advantages of simplicity, rapidity, selectivity and higher sensitivity than most of the existing spectophotometric methods.

• Korean Journal of Veterinary Service
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• v.18 no.3
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• pp.13-28
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• 1995

This study was carried out to explore the most sensitive and useful method for simultaneous determination of five sulfa drugs(sulfamethazine, sulfamerazine, sulfamonomethoxine, sulfadimethoxine, sulfaquinoxaline) in livestock productions(pork muscle, bovine muscle, chicken muscle, milk ) by HPLC with UV detector and reverse phase column. The results obtained were as follows：1. For mobile phase acetonitrile-0.01M ammonium acetate (23：77) showed more applicable sensitivity and retention times than acetonitrile-1% acetic acid(23：77). Thus acetonitrile-0.01M ammonium acetate(23：77) selected and applied to the modification test, from which it was found pH 6.75 was the most adequate. 2. Optimal wavelength of UV for SMT(sulfamethazine), SMR(sulfamerazine), SMM(sulfamonomethoxine), SD(sulfadimethoxine), and SQ(sulfaquinoxaline) were 266, 266, 265, 269 and 250nm, respectively, and that for simultaneous application it was 263nm. 3. The average recovery rate by extractant(chloroform, dichloromethane, chlorform+dich-loromethane) in the classic method was not significantly different(p>0.05) but that by chloroform higher than the others. Thus chloroform was found to be adequate as extractant in this classic method. 4. The average recovery rate was 86.5% by the MSPD(matrix solid phase disperse) method, which was significantly higher than that by the classic method(p<0.05). Also the recovery rates by method were significantly different(p<0.05) in accordance with sample and type of drug. The MSPD method was much superior to classic method on clean-up.

• Journal of Electrochemical Science and Technology
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• v.11 no.1
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• pp.68-83
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• 2020

A fast and simple method for synthesis of Cu_xO-ZnO/PPy/RGO nanocomposite by electrochemical manner have been reported in this paper. For testing the utility of this nanocomposite we modified a GCE with the nanocomposite to yield a sensor for simultaneous determination of four analytes namely ascorbic acid (AA), dopamine (DA), uric acid (UA), and folic acid (FA). Cyclic voltammetry (CV) and Differential pulse voltammetry (DPV) selected for the study. The modified electrode cause to enhance electron transfer rate so overcome to overlapping their peaks and consequently having the ability to the simultaneous determination of AA, DA, UA, and FA. To synthesis confirmation of the nanocomposite, Field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and electrochemical impedance spectroscopy (EIS) were applied. The linearity ranges were 0.07-485 μM, 0.05-430 μM, 0.02-250 μM and 0.022-180 μM for AA, DA, UA, and FA respectively and the detection limits were 22 nM, 10 nM, 5 nM and 6 nM for AA, DA, UA, and FA respectively Also, the obtained electrode can be used for the determination of the AA, DA, UA, and FA in human blood, and human urine real samples.