Dongjin Pyo

Addition of methanol to the mobile phase in packed capillary column supercritical fluid chromatography. Retention mechanisms from linear solvation energy relationships

Linear solvation energy relationships (LSERs) were used to verify previously proposed retention mechanisms when an organic modifier is used with an octyldecylsilane bonded phase in packed capillary column supercritical fluid chromatography. Supercritical fluid chromatographic retention data for a wide variety of compounds at different modifier concentrations were obtained using a 60 cm×200 μm I.D. ODS packed capillary column. Supercritical carbon dioxide at a pressure of 260 atm was used as mobile phase and methanol as modifier. The LSER regression equation used was log k′ = SP0 + llog L16 + s π2H + αα2H + bβ2H + rR2, where k′ represents the capacity factor and L16 represents the partition coefficient of the solute between the gas phase and n-hexadecane at 298 K, and l, s, a, b and r are the regression coefficients. By increasing the percentage of modifier added to the mobile phase, the l coefficient decreased gradually. The b and s coefficients were greatly decreased on moving from neat carbon dioxide mobile phase to 2% methanol modifier, thereafter showing a gradual decrease with increasing modifier concentration. From these observations, we substantiate the conclusion that when a small amount of modifier (up to 2%) is added, the predominent modifier effect on the ODS bonded phase is dynamic coating of free silanols on the surface of the stationary phase, and when more modifier is added, another effect, i.e. an increase in the density of the mobile phase leading to an increase in elution strength of the eluent, becomes more important.

Simultaneous determination of bisphenol A, chlorophenols and alkylphenols by solid-phase extraction and HPLC

An analytical method for determining potential endocrine disruptors (bisphenol A, 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, pentachlorophenol, p-t-butylphenol, p-pentylphenol, p-hexylphenol, pt-octylphenol, p-heptylphenol, nonylphenol) by solid-phase extraction (SPE) and High Perfomance Liquid Chromatography(HPLC) equipped with fluorescence and variable wavelength detector has been developed. The SPE process for sample concentration was performed on a commercially available Oasis HLB cartridge packed with polymeric sorbents. The effect of elution solvent and elution volume on the recoveries of the analytes were investigated with HPLC. Average recovery of >85% was achieved with 60mg sorbents using 5mL of methanol as elution solvent. Phenolic compounds in canned drinks, beverages and water samples were surveyed by this proposed method.

Addition and Measurement of Methanol in Carbon Dioxide Mobile Phase for Supercritical Fluid Chromatography

A simple method for the addition of methanol to supercritical CO 2 is described. Carbon dioxide, the most widely used mobile phase in supercritical fluid chromatography, is a relatively non-polar fluid, and hence addition of small amounts of polar modifiers could be necessary to migrate polar solutes. In this paper, a new mixing device was developed, in which high porous stainless steel filters were used to generate methanol modified carbon dioxide mobile phase. When supercritical CO 2 goes through the mixing device, the modifiers held within the small pores of filters can be dissolved in the pressurized supercritical fluids. High porous stainless steel filter with 2 μm porosity was used in our mixing device. To measure the amount of methanol dissolved in supercritical CO 2 after the mixing device, a fuel cell type modifier sensor, which was made by depositing gold and platinum on a porous plastic disc was used.

Supercritical fluid chromatographic detection by use of a parallel flow restrictor

Abstract In supercritical fluid chromatography (SFC), the role of the flow restrictor is not only to maintain supercritical conditions throughout the column but also to provide the necessary interface between the column and the detector. In the previous paper,1 a new type of flow restrictor called parallel flow restrictor was introduced. At that time, the parallel flow restrictor was used only for the flow control. In this paper, the parallel flow restrictor was used not only for the flow control but also for the interface to the second detector. A supercritical fluid chromatographic system with a combination of two detectors based on physically different principles, flame ionization and UV absorption, was used.

Determination of phenol using solid-phase extraction and HPLC/MSD/FLD in water

Abstract: An analytical method for determining phenol considered priority pollutants of the US EPA andprecursor of toxic phenolic compounds by solid-phase extraction (SPE) and high performance liquidchromatographic systems (HPLC) equipped with fluorescence and mass selective detectors have been developed.The SPE process for sample preconcentration was performed on a commercially available Oasis HLB cartridgepacked with polymeric sorbents. The effect of pH, elution solvent, and elution volume on the recoveries ofthe analytes were investigated with HPLC/FLD. Average recovery of >87.0% was achieved with 60 mg sorbentsusing 5 mL of methanol as an elution solvent at pH=3.요약: Priority pollutant이며 페놀성화합물의 전구체인 페놀을 고체상추출법을 이용하여 추출 정제하여형광검출기와 질량분석기가 각각 장착된 고속액체크로마토그래프를 이용하여 분석하는 방법을 설정하여보았다. 고체상추출은 고분자성물질이 충진된 Oasis HLB cartridge를 이용하여 최적의 조건을 확립하였으며 이때의 평균회수율은 87.0% 이었다. 형광검출기를 이용한 경우가 질량분석기를 이용한 경우보다검출한계가 낮았으나 선택성의 측면에서 질량분석기가 우수하였다. Key words: phenol, hplc, solid phase extraction(spe), hplc/msd