• Journal of Pharmaceutical Investigation
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• v.30 no.1
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• pp.51-54
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• 2000

A column-switching high performance liquid chromatographic method has been developed for the determination of a fluconazole in human plasma. Each plasma sample was centrifuged for 10 min at 5000 g. After an aliqout of the supernatant was taken to nylon microcentrifuge filter, these samples were centrifuged for 10 min at 5000 g. An aliqout of the supernatant was injected directly onto the HPLC column. Deionized water was run for 2 min at a flow rate of 1.0 ml/min to retain fluconazole in an extration column, while proteins and endogenous interferences were eluted to the waste. The analyte was then back-flushed onto an analytical column, $C_{18}$ reversed-phase column. The mobile phase for analytical column, 0.01 M sodium acetate (pH 5.0)-methanol (65:35, v/v), was run at a flow rate of 1.0 ml/min. The column effluent was monitored by ultraviolet detection at 261 nm. The retention time for fluconazole was 11.76 min in human plasma. The detection limit for fluconazole in human plasma was $0.2\;{\mu}g/ml$. No interference from endogenous substances was observed.

• Analytical Science and Technology
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• v.28 no.2
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• pp.125-131
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• 2015

A method was developed and fully validated for the determination of terbutaline, a β₂-receptor agonist, in human plasma. Plasma samples were prepared by solid-phase extraction with Sep-Pak silica, followed by high-performance liquid chromatography (HPLC). The terbutaline was pre-separated from the interfering components in plasma on a Luna C18 (2) column, and terbutaline and salbutamol as an internal standard were resolved and determined on a Luna Silica column. The two columns were connected by a switching valve equipped with silica pre-column. The pre-column was used to concentrate the terbutaline in the eluent from the C18 column before back-flushing onto the silica column with fluorescence detection at an excitation/emission wavelength of 276/306 nm. The method was shown to be specific by testing six different human plasma sources. Linearity was established for a concentration range of 0.4-20.0 ng/mL with a correlation coefficient of 0.9999. The lower limit of quantitation was 0.4 ng/mL with a precision of 10.1% as C.V.%.

• Archives of Pharmacal Research
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• v.23 no.5
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• pp.441-445
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• 2000

Achiral-chiral column switching HPLC assay was developed to allow the separation and quantification of the enantiomers of terbutaline in human plasma by means of fluorescence detection. Plasma samples were prepared by solid-phase extraction with sep-pak silica, followed by HPLC assay. The enantiomers of terbutaline and the internal standard were separated from the biological matrix on a silica column, and the two enantiomers were resolved and quantified on a Sumichiral OA-4900 column. The two columns were connected by a switching valve equipped with silica trap column, The trap column was used to concentrate the terbutaline in the eluent from the achiral column before back flushing onto the chiral phase. For each enantiomers, the assay was linear between 2.5-125 ng/$m\ell$ (r=0.9999) and detection limit was 1.0 ng/$m\ell$ .

• Journal of the Korean Vacuum Society
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• v.21 no.6
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• pp.312-321
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• 2012

The electric potential of plasma column is measured with the high voltage probe in a pair of atmospheric plasma jets operated by AC-voltage. According to the polarity of voltage applied to the electrodes, the polarity of plasma column potential has the same polarity of applied voltage. The high potential of plasma column at the side of high voltage electrode is decreased linearly along the plasma column to the ground side. Therefore, the plasma column seams to be a kind of resistor whose resistivity is a few 10s $M{\Omega}/m$. In the experiment of double-jets system, the polarity of plasma potential is verified to be the same polarity to the applied voltage. When the different voltage polarities are applied to the electrodes of double plasma jets, the attractive force is acted between two plumes at the merged plasma and the plasma potential is measured to be low as a few 10s V. When the same polarity of voltage is applied to the electrode, the repulsive force is acted and the plasma potential is measured to be high as a several 100s V at the merged plumes. In the exposure of plasma plume on the bio-substrate with the double plasma jets, the electric shock and thermal damage might be proportional to the plasma power which is the multiplication of the plasma potential and the plasma current.

• Archives of Pharmacal Research
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• v.17 no.6
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• pp.458-461
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• 1994

A new high-performance liquid chromatographic method with column switching has been onto a Bondapak phenyl/corsil $(37-50{\;}{\mu}m)$ precolumn and polar plasma components were washed with 0.06 M borate burffer. After valve switching, the concentrated drug were eluted in the back-flush mode and separated on a ${\mu}-Bondapak$ C18 column with acetonitrilke-phosphate buffer as the mobile phae. The method showed excellent precision, accuracy and speed with detection limit of $0.01{\;}{\mug}/ml^{-1}$. Total analysis time per smaple was less than 20 min and the coefficients of variation for intra and inter-assay were less than 5.635. This method has been successfully applied to plasma smaples from eats after oral administration of omeprazole.

• Archives of Pharmacal Research
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• v.24 no.3
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• pp.207-210
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• 2001

A fully automated high performance liquid chromatography with column-switching was developed for the simultaneous determination of KR60436, a new reversible proton pump inhibitor, and its active metabolite O-Demethyl-KR60436 from rat plasma samples. Plasma sample (50$\mu$l) was directly introduced onto a Capcell Pak MF Ph-1 column ($10{\times}4$ mm I.D.) where primary separation was occurred to remove proteins and concentrate target Substances Using acetonitrile-Potassium Phosphate (PH 7, 0.1 M) (2 : 8, v/v). The drug molecules eluted from MF Ph-1 column were focused in an intermediate column ($10{\times}2$ I.D.) by the valve switching step. The substances enriched in intermediate column were eluted and separated on a Vydac 218MR53 column ($250{\times}3.2$ I.D.) using acetonitrilepotassium phosphate (pH 7, 0.02 M) (47:53, v/v) at a flow rate of 0.5 ml/min when the valve status was switched back to A position. The method showed excellent sensitivity (detection limit of 2 ng/ml) with small volume of samples ($50{\mu}$l), good precision and accuracy, and speed (total analysis time 24 min) without any loss in chromatographic efficiency. The response was linear ($r^2{\geq}0.797$) over the concentration range of 5-500 ng/ml.

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.398.2-398.2
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• 2002

A column switching HPLC assay was developed to allow the separation and quantitation of cetirizine in human plasma by ultraviolet (UV) detection. Plasma samples were prepared by liquid-liquid extraction. After drying, the residue was reconstituted in 20 mM phosphate buffer (pH 2.8) containing 15% acetonitrile. The samples were initially injected onto a clean-up Capcell Pak MF C18 column. (50 mm $\times$ 4.6 mm I.D.), and the chromatographic region containing the peaks of interest was followed in an analytical C18 microcolumn (250 mm$\times$1.5 mm I. D.) via column switching device. (omitted)

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.59-63
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• 2003

Modal properties of guided waves along circular dispersive double negative (DNG) index metamaterial rod waveguides are numerically investigated. Identical forms of dispersive dielectric and magnetic material constants are used for simplicity. For degenerated azimuthally symmetric mode, a multimode region, a single mode region, a band gap region and a forbidden region are found which cannot be observed in the case of the conventional dielectric rod waveguide. As the normalized frequency goes down, discrete guided modes are continuously generated, which is a reverse property of conventional dielectric rod waveguide. Also, there are high-frequency cutoffs, which have been generally examined in dispersive circular geometries such as a plasma column or a plasma Goubau line. In the single mode region, both the low- and high-frequency cutoffs are existed where the propagation constants are continued between the guided oscillating and surface modes.

• Proceedings of the PSK Conference
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• 2003.04a
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• pp.278.2-278.2
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• 2003

A column-switching semi-micro HPLC method with fluorescence detection was developed for the direct analysis of rebamipide in human plasma. Plasma was filtered through a 0.45 $\mu\textrm{m}$ membrane filter and 5 ${\mu}\ell$ of the filtrate was directly injected onto the pre-column. After elution of the plasma proteins to waste, the retained rebamipide and internal standard(ofloxacin) were transferred to a C18 semi-microcolumn (5$\mu\textrm{m}$, 150 ${\times}$2.0mm) where they were separated using acetonitrile-1.4％ acetic acid (40:60, v/v) as mobile phase. (omitted)

• Analytical Science and Technology
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• v.37 no.2
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• pp.123-129
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• 2024

We present a rapid method for the determination of Cs, Sr, and Ba, heat generators found in highly active liquid wastes, by gas-pressurized extraction chromatography (GPEC) using a column containing a cation-exchange resin. GPEC is a microscale column chromatographic technique that uses a constant flow rate of solvent (0.07 mL/min) with pressurized nitrogen gas supplied through a valve. In particular, because this method uses a small sample volume (a few hundred microliters), it produces less chemical waste and allows for faster separation compared to traditional column chromatography. In this study, we evaluated the separation of Cs, Sr, and Ba using GPEC. The eluate from the column (GPEC or conventional column chromatography) was quantitatively analyzed using inductively coupled plasma-mass spectrometry to measure the column recovery and precision. The column reproducibility of the proposed GPEC system (RSDs of recoveries) ranged from 2.7 to 4.1 %, and the column recoveries for the three elements ranged from 72 to 98% when aqueous HCl was used as the eluent. The GPEC results are slightly different in efficiency and separation resolution compared to those of conventional column chromatography because of the differences in the eluent flow rate as well as the internal diameter and length of the column. However, the two methods had similar recoveries for Cs and Sr, and the precision of GPEC was improved by two-fold. Remarkably, the solvent volume required for GPEC analysis was five times lower than that of the conventional method, and the total analysis time was 11 times shorter.