• Journal of Korean Society for Atmospheric Environment
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• v.34 no.4
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• pp.616-624
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• 2018

In this study, a previous DNPH (2,4-dinitrophenylhydrazine) coupled with high performance liquid chromatography (HPLC) method to measure the concentration of formaldehyde in ambient and source environments has been improved. To improve the disadvantage of the previous HPLC method, an appropriate composition ratio of mobile phase (water: acetonitrile (ACN)) was determined and an isocratic analysis was conducted. Furthermore, limit of detection (LOD), limit of quantitation(LOQ), accuracy, and precision were investigated to verify the reliability of the analytical conditions determined. Finally, samples of exhaust gases from five different industrial facilities were applied to HPLC analytial method proposed to determine their formaldehyde concentrations. The appropriate composition ratio of the mobile phase under the isocratic condition was a mixture of water(40%) and ACN(60%). As the volume fraction of the organic solvent ACN increases, retention time of the formaldehyde peak was reduced. Detection time of formaldehyde peak determined using the proposed isocratic method was reduced from 7 minutes(previous HPLC method) to approximately 3 minutes. LOD, LOQ, accuracy, and precision of the formaldehyde determined using standard solutions were 0.787 ppm, 2.507 ppm, 93.1%, and 0.33%, respectively, all of which are within their recommended ranges. Average concentrations of the formaldehyde in five exhaust gases ranged from 0.054 ppm to 1.159 ppm. The lowest concentration (0.054 ppm) was found at samples from waste gas incinerator in a bisphenol-A manufacturing plant. The highest was observed at samples from the absorption process in manufacturing facilities of chemicals including formaldehyde and hexamine. The analytical time of the formaldehyde in ambient air can be shortened by using the isocratic analytical method under appropriate mobile phase conditions.

• FOCUS: LIFE SCIENCE
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• no.1
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• pp.9.1-9.5
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• 2024

Method development for complex low molecular mass (LMM) samples using reversed-phase (RP) separation conditions presents significant challenges due to the presence of many unknown analytes over wide concentration ranges. This guide aims to optimize method parameters-column length (L), temperature (T), flow rate (F), and final mobile phase conditions (Øfinal)-to maximize separation peak capacity. Validated by prior research, this protocol benefits laboratories dealing with metabolomics, natural products, and contaminant screening. This practical guide provides a structured approach to maximizing peak capacity for complex LMM separations. It complements computational optimization strategies and offers a step-by-step method development process. The Snyder-Dolan test is highlighted as essential for determining the need for gradient or isocratic elution and guiding column length decisions. The decision tree framework helps analysts prioritize variable optimization to develop effective separation methods for complex samples.

• Natural Product Sciences
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• v.12 no.1
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• pp.55-61
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• 2006

A description of simple, isocratic and precise reversed phase HPLC methods is given for simultaneous quantification of pholcodine and ephedrine hydrochloride together with either carbinoxamine maleate or terfenadine in antitussive-antihistaminic oral pharmaceutical formulations. Separations were carried out on X-Terra and symmetry shield C18 column $(250\;{\times}\;4.6\;mm,\;5\;{\mu}m)$. The used isocratic elution systems were either $0.02\;M\;KH_2PO_4-acetonitrile$ in the ratio of 75 : 25 and pH adjusted to 7.70 with orthophosphoric acid or sodium hydroxide, for syrup (method A), or 0.02 octanesulphonic acid sodium salt solution-acetonitrile-acetic acid in the ratio of 75 : 25 : 0.5 for suspension (method B). The elution of both mixtures was achieved with a flow rate of 1 ml/min. Detection was carried out by UV absorbance at wavelengths of 220 and 250 nm for syrup and suspension, respectively. The quantification of the components in synthetic mixtures and actual syrup and suspension were calculated using the internal standard technique with metoclopramide HCl and codeine phosphate as internal standards (IS), respectively. The methods, for both mixtures, were validated and met all the requirements for the quality control analysis recommended by FDA and ICH.

• The Korean Journal of Food And Nutrition
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• v.9 no.2
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• pp.213-216
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• 1996

A modified method is given for the precolumn derivatization and subsequent high-pressure liquid chromatographic seperation of 3-methylhistidine from urine. The elution contained isocratic solution with acetonirile and 10 M sodium phosphate(pH 7.5) requires less than 7 min. The recoveries of 3-methylhlstidine from urine control were 95% to 106%. 3-Methylhistidine determinations were performed on urine samples from volunteers who were both male trained and non-trained physical undergraduates. As the result, urinary .3-methylhistidine content of volunteers increased significantly after weight training.

• The Korean Journal of Physiology and Pharmacology
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• v.2 no.6
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• pp.779-786
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• 1998

A reversed-phase high-performance liquid chromatogrphy (RP-HPLC) has been developed to analyze the metabolites of arachidonic acid based on the specificities of ultraviolet absorption of these various metabolites and is sensitive to the nanogram level. This procedure makes it possible to extract complex mixtures of eicosanoids efficiently with a single step and to analyze them simultaneously by RP-HPLC from biological samples using octadesylsilyl silica extraction column and $PGB_2$ as an internal standard. The cyclooxygenase products {prostaglandin $(PG)D_2,\;PGE_1,\;PGE_2,\;PGF_{1{\alpha}},\;PGF{2{\alpha}},\;6-keto-PGF_{1{\alpha}},$ and thromboxane $B_2(TXB_2)}$ and lipid peroxidation product, isoprostanes, of arachidonic acid were monitored by one isocratic HPLC system at 195 nm wavelength. The lipoxygenase products ${leukotriene(LT)B_4,\;LTC_4,\;LTD_4,$ and 5-hydroxyeicosatetraenoic acid (5-HETE), 12-HETE, 15-HETE} were measured by another isocratic HPLC system at 280 nm for LTs and 235 nm for HETEs. This method provides a simple and reliable way to extract and assess quantitatively the final arachidonic acid metabolites.

• Natural Product Sciences
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• v.17 no.2
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• pp.104-107
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• 2011

In order to facilitate the quality control of betaine from the fruits of Lycium chinense, we have developed a rapid and simple method for quantitative determination. Determination was achieved on a Discovery C18 column with an isocratic solvent system of 0.32% perfluoropentanoic acid aqueous-acetonitrile at a flow-rate of 0.5 mL/min and detected an ELSD. The method was reproducible with intra- and inter-day variations of less than 6% (R.S.D). The recoveries were in the range of 90.01~100.05%. The method turned out to be fast and simple, furthermore, to have a good selectivity and sensitivity for the quantity determination of betaine in the fruits of L.chinense.

• Journal of Applied Biological Chemistry
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• v.42 no.4
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• pp.191-196
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• 1999

A multiresidue analytical method was developed for eight acaricides including benzoximate, clofentezine, fenazaquin, fenothiocarb, fenpyroximate, hexythiazox, pyridaben, and tebufenpyrad in four major fruits using high-performance liquid chromatography (HPLC). All the confounds were extracted with acetone from apple, pear, grape, and citrus samples. The extract was diluted with saline water, and n-heaxane partition was followed to recover the acaricides. Florisil column chromatography was employed to further purify the sample extract. HPLC with ultraviolet absorption detection, using an octadecylsilyl column under the isocratic mobile phase of acetonitrile/water mixture, was successfully applied to separate and quantitate all the compounds in the purified extract. Recoveries of the eight acaricides from for fortified samples ranged 86.4~97.0%. Relative standard deviations of the analytical method were all less than 10%. Detection limits of the method were in the range of 0.02~0.05 mg/kg. The proposed method was reproducible and sensitive enough to evaluate the terminal residue of the eight acaricides in the fruit harvest.

• Analytical Science and Technology
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• v.20 no.3
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• pp.255-260
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• 2007

A new method for the simultaneous determination of low molecular weight amines and quaternary ammonium ions based on the separation by IC with a suppressor and the detection by MS with ESI has been developed. The method has been applied to the analysis of a mixture containing tetramethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion, triethanolamine, trimethylamine and triethylamine. The constituents were separated by isocratic elution using an IonPac CS17 column, a cation-exchange column, and detected by conductivity and mass spectrometry. The newly developed method for the six components demonstrated that the repeatability in terms of relative standard deviation for three measurements was in the range of 0.1-0.5 %. The detection limits were between 0.2 and $0.9{\mu}g/mL$ by the IC/ESI-MS.

• Asian-Australasian Journal of Animal Sciences
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• v.1 no.2
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• pp.99-106
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• 1988

A high performance liquid chromatographic procedure is described for the direct determination of the picomole amount of palmitoyl-Coenzyme A and stearoyl-Coenzyme A, using a stainless steel column packed with C-18 derivatized porous silica ($5{\mu}m$), an isocratic elution with a mixture of 33 mM $KH_2PO_4$/acetonitrile as a mobile phase and a UV detector. The long-chain acyl-Coenzyme A esters were determined in incubated microsomal fractions of a bovine liver to demonstrate the utility of this method for monitoring acyl-CoA synthesis in biological samples. The reaction rate of palmitate was higher than that of stearate. After a 60 minute incubation period, the generated amount of palmitoyl-Coenzyme A and stearoyl-Coenzyme A were approximately 70 and 20 n mol/mg micresomal protein, respectively. The advantage of this method are in that no decomposition of the CoA esters is involved, while the constituent molecular species is detected.

• KSBB Journal
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• v.15 no.1
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• pp.60-65
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• 2000

In order to predict the chromatogram for organic acid in ion chromatography, Langmuir isotherm parameters were obtained by Retention Time Method (RTM) and moment method. Ion chromatography analysis for formic acid was performed and compared with theoretically predicted profiles under isocratic condition. Band profiles were estimated with the equilibrium-dispersive model of chromatography using a PDEsolver Macsyma . The relationship between the characteristics of chromatogram and the variable operating condition in chromatography such as the flow rate, ionic strength and injection volume was studied. Satisfactory agreement was observed between the experimental and the estimated chromatograms with parameters obtained form the moment method.