• Journal of the Korean Society of Food Science and Nutrition
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• v.28 no.6
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• pp.1208-1211
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• 1999

Semi HPLC using a column switching technique was used to determine the trace content of vitamin B12 in various foods. Total analytical time required less than 20 mins per sample and the recovery ratio was 99.9, 99.6, 100.1 and 99.8% for 1.0, 10.0, 100.0 and 1,000 g/kg, respectively. The content of vitamin B12 in various foods obtained using column switching method showed higher levels compared to labels in dried milk(0.5 g/100g) and in grain products(0.51~34.36 g/100g). Thus, this column switching method was more sensitive, effective and precise than the microbiological analysis currently used to determine the trace compounds like a vitamin B12.

• Korean Journal of Food Science and Technology
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• v.37 no.6
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• pp.1024-1027
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• 2005

Rapid and simple method was developed for simultaneous determination of vitamins $D_3\;and\;K_1$ contents in infant formula. Contents of vitamins $D_3\;and\;K_1$, extracted by column-switching HPLC with reversed phase column using enzymatic hydrolysis and organic solvent, in CRM determined by developed method were within certified ranges of standard values.

• 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.

• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3629-3634
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• 2013

In this study, an improved method for the quantitative analysis of ginkgolic acids (GAs) in Ginkgo biloba leaf extract was developed. The samples were extracted with a mixture of chloroform and 50 % ethanol, after which the chloroform extract was dried and reconstituted in methanol. GAs with 13:0, 15:1, and 17:1 in the extract were successfully separated within 40 min and determined with high throughput performance using an online column-switching HPLC method using an SP column C8 SG80 ($4.6{\times}150mm$, $5{\mu}m$) and a Cadenza 5CD C18 column ($4.6{\times}150mm$, $3{\mu}m$). The developed HPLC method was validated for Ginkgo biloba leaf extract. The validation parameters were specificity, linearity, precision, accuracy, and limits of detection and quantitation (LODs and LOQs, respectively). It was found that all of the calibration curves showed good linearity ($r^2$ > 0.9993) within the tested ranges. The LODs and LOQs were all lower than $0.04{\mu}g/mL$. The established method was found to be simple, rapid, and high throughput for the quantitative analysis of GAs in ten commercial Ginkgo biloba leaf extract and dietary supplements. The samples were also analyzed in LC-electrospray ionization (ESI) tandem mass spectrometry (MS/MS) - multiple-ion reaction monitoring (MRM) mode to confirm the identification results that were obtained by the column switching HPLC-DAD method. The developed method is considered to be suitable for the routine quality control and safety assurance of Ginkgo biloba leaf extract.

• 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/$m\ell$ .

• Proceedings of the PSK Conference
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• 2003.04a
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• pp.281.1-281.1
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• 2003

Purpose. The purpose of this study was to develop and validate sensitive and specific analytical method for determinination of simvastatin in human plasma by the column-switching high-performance liquid chromatography (HPLC) system with UV detection. Methods. Simvastatin and internal standard were extracted into diethyl ether from plasma. (omitted)

• 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.

• Analytical Science and Technology
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• v.15 no.6
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• pp.529-533
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• 2002

The separation and determination method of racemic isomers of flurbiprofen in urine samples have been investigated using column switching- HPLC, which include the sample treatment and concentration column. The optical rotation of two isomers separated were measured to identify d-form and l-form. The calibration curves are liear in the ranges of $0.11-5.4{\mu}g/mL$ for both d-form and l-form. The detection limits were $0.031{\mu}g/mL$ for l-isomes and $0.027{\mu}g/mL$ for d-isomer. The coefficients of variation of intra-day and inter-day precision of this method were about 1.8%. The present method was apllied to determine the concentration of racemic isomers in urine sample from human eating the drug.

• Preventive Nutrition and Food Science
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• v.8 no.4
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• pp.301-305
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• 2003

This study was conducted to develop an HPLC method for determining vitamin B$_{12}$ in fortified foods which has typically been determined by microbiological assays according to AOAC and Korean Food Code approved methods. Vitamin B$_{12}$ (cyanocobalamin) was determined by reversed-phase HPLC with a triple column and UV/VIS dectector (550 nm) using the column switching technique after extraction with 5 mM potassium phosphate solution by sonication without a clean-up procedure. The recovery of spiked samples and limit of detection (LOD) by HPLC were 78.6 ∼107.5 % and 2 ppb ($\mu\textrm{g}$/kg), respectively. The LOD of the microbiological assay (MBA) was much lower than that of HPLC. The concentrations of vitamin B$_{12}$ analyzed in all tested samples (n=12) confirmed compliance with declared label claims. The range of recovery ratio by the HPLC method when compared to the microbiological assay was 76.2 ∼140.0 %. There was not significant difference between the HPLC and MBA methods (p < 0.01) with r=0.9791 and linear regression y=0.9923x-0.04. The HPLC method for determining vitamin B$_{12}$ using the column-switching technique appears to be suitable for determining vitamin B$_{12}$ concentrations above 1 $\mu\textrm{g}$/100 g in fortified foods.ied foods.

• Archives of Pharmacal Research
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• v.21 no.2
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• pp.212-216
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• 1998

A coupled achiral-chiral high-performance liquid chromatographic system has been developed for the determination of the enantiomers of salmeterol, S-(+)-salmeterol and R-(-)-salmeterol in urine. THe salmeterol was separated from the interfering components in urine and quantified on the silica column, and the enantiomeric composition was determined on a Sumichiral OA-4700 chiral stationary phase. The two columns were connected by a switching valve equipped with a silica precolumn. The two columns wer connected by a switching valve equipped with a silica precolumn. The precolumn was used to concentrate the salmeterol in the eluent from the achiral column before backflushing onto the chiral phase. The coupled system was validated.