• 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/$m\ell$ .

• 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.

• Journal of The Korean Society of Inherited Metabolic disease
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• v.15 no.2
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• pp.65-71
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• 2015

Since the secretion of specific chiral isomers in urine (or plasma) is very crucial to diagnose some inborn metabolic disorders, clinical application of dual column achiral differential method has been performed for the absolute configuration of chiral compounds. Extracted from the acidified urine with diethyl ether, carboxylic functional group of organic acid (stereoisomers of the volatile) was derivatized with (-)-menthylation or (S)-(+)-3-methyl-2-butylation and followed by O-trifluoroacylation. Each of the enantiomers was accurately separated from the library matched double column (achiral) with a retention index (I). In various inborn metabolic disease urines, absolute chirality was identified correctly in the urine (10 patients) with inborn metabolic disease (including secretion of D, L- lactic acid, D, L-3-hydroxybutyric acid, and D, L-2-hydroxyglutaric acid). In this study, we identified and isolated the volatile diastereomer as a useful diagnostic marker, this successful application to urine specimens may be useful for diagnostic classification of inherited metabolic disorders.

• Analytical Science and Technology
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• v.9 no.1
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• pp.52-61
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• 1996

Detectable levels of several free D-amino acids were found in some food. This was accomplished by using a column switching method. The determination of total amount of D- and L-amino acids was based on an achiral separation with a $C_{18}$ column. The level of D-amino acids to L-amino acids was determined by the column switching system including the postcolumn reaction detection of the amino acids derivatized with O-phthalaldehyde. The chiral separation of the postcolumn detection system was carried out with chiral crown ether column. This system was applied for the micro-determination of D-amino acids in food such as soy sauce, fermented soy bean and beans. It turned out that the sampling process is critical for the trace analysis of D-amino acids under this achiral / chiral coupled-column system. It was found that commercial soy sauce contained 42ppm, conventional soy sauce 102ppm, fermented soy bean 8.34mg per 1g and bean 2.87mg per 1g sample for phenylalanine. D-phenylalanine was found 0.67% in commercial soy sauce, 0.34% in conventional soy sauce, less than 1.81% in fermented soy bean, and Jess than 2.82% in bean.

• Journal of the Korean Chemical Society
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• v.39 no.4
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• pp.257-265
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• 1995

Free amino acids were isolated from milk and their absolute amounts were determined by reversed phase high performance liquid chromatography after derivatization with dansyl chloride. The determination of D- and L-amino acids was based on achiral separation on a C18 column. It was found that milk contained totally 41.00 mg DL-amino acids in 100 mL milk. The level of D-amino acids to L-amino acids was determined by a column-switching system combining an achiral reversed phase separation and chiral chelate additive. The chiral separation was carried out with addition of the chiral Cu(N-benzyl-L-proline)2 chelate to the mobile phase in reversed phase liquid chromatography. It was found that the determination of 16 different amino acids is feasible in the milk sample with a C18 column separation and 12 D-amino acids out of the 16 amino acids can be determined via the column-switching system with chiral separation. 2.05% of D-glutamic acid and 2.93% of D-alanine were found in milk.

• Archives of Pharmacal Research
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• v.26 no.2
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• pp.114-119
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• 2003

A high performance liquid chromatographic (HPLC) method was developed for the qualitative and quantitative determination of benzophenanthridine alkaloids from the methanol extracts of Hylomecon hylomeconoides and H. vernale (Papaveraceae). Achiral and chiral methods were adapted for the separation of 6-methoxydihydrosanguinarine (1), 6-acetonyldihydrosanguinarine (2) and dihydrosanguinarine (3). The achiral reversed phase HPLC method made it possible the simultaneous separation and determination of 1, 2 and 3 within 20 min on ODS column using acetonitrile-phosphate buffer (50 mM, pH 7.0) (50 : 50, v/v). The separation and determination of 1 and 2 enantiomers was available using chiral columns. The same amount of (+) and (-)-enantiomers of 1 was found from the methanol extract of specimen, indicated that 1 could be the artifact produced by the reaction of sanguinarine with methanol. H. hylomeconoides showed higher level of 1 and 3 in compared with H. vernale, especially in root samples permitting the possibility of chemical discrimination between two species.

• Analytical Science and Technology
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• v.33 no.2
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• pp.59-67
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• 2020

Nadolol is a β-blocker drug, which effectively manages hypertension and angina pectoris. Its chemical structure allows the formation of four possible stereoisomers. A coupled column high-performance liquid chromatographic (HPLC) system with UV and fluorescence detection was investigated for simultaneously determining four nadolol enantiomers in human plasma. The plasma samples were prepared using a convenient liquid-liquid extraction process and passed through HPLC. Nadolol was initially separated from the endogenous compounds or other impurities in human plasma on a Phenomenex silica column, and its enantiomers were resolved and determined on a Chirapak AD-H column. The developed HPLC method achieved an effective chiral separation and significantly eliminated endogenous compound interference. This optimal HPLC method was validated following FDA guidelines. The results showed good selectivity, linearity, accuracy (90.50 % - 105.27 %), and precision (RSDs < 9.52 %) for each enantiomer. This method was also successfully applied to determine nadolol enantiomers in the plasma samples of a healthy male volunteer (after orally administering 80 mg racemic nadolol), proving its suitability for nadolol stereoselective pharmacokinetic studies.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2418-2422
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• 2011

The enantiomeric separation of lactic acid for its absolute configuration has become important task for understanding its biological origin and metabolic process involved in the formation of lactic acid. It involves the conversion of enantiomers as diastereomeric O-pentafluoropropionylated (S)-(+)-3-methyl-2-butyl ester and the direct separation by gas chromatography-mass spectrometry on a achiral capillary column. The (R)- and (S)-lactic acids were completely separated with a high resolution of 1.9. The newly developed method showed good linearity (r ${\geq}$ 0.999), precision (% relative standard deviation = 3.4-6.2), and accuracy (% relative error = -7.7-1.4) with the detection limit of 0.011 ${\mu}g/mL$. When the method was applied to determine the absolute configuration of lactic acid in Lactobacillus delbrueckii subsp. lactis 304 (LAB 304), the composition (%) of (R)-lactic acid in the cell pellet and in the culture medium were $89.0{\pm}0.1$ and $78.2{\pm}0.4$, respectively. Thus, it was verified that the present method is useful for the identification and composition test of lactic enantiomers in microorganisms.

• Archives of Pharmacal Research
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• v.26 no.9
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• pp.763-767
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• 2003

The differences in pharmacokinetic behavior and tissue distribution of verapamil and its enantiomers were investigated in rats. In high-performance liquid chromatographic method, an achiral ODS column (150 mm $\times$ 4.6 mm i.d.) with the mobile phase consisting of methanol-water (73:30, v/v) was used for the determination of the concentration for racemic verapamil, and a Chiralcel OJ column (250 mm$\times$4.6 mm i.d.) with the mixture of n-haxane-ethanol-triethylamine (85:15:0.2, v/v/v) as mobile phase was used to determine the concentrations of verapamil enantiomers. A fluorescence detector in the analytical system was set at excitation and emission wavelengths of 275 nm and 315 nm. The differences between enantiomers were apparent in the pharmacokinetics in rats. The area under the concentration-time curve (AUC) of S-(-) verapamil was higher than that of R-(+) verapamil. The half-distribution time ($T_{1/2(\alpha)}$) of S-(-) verapamil which distributing to tissue from blood was shorter than that of R-(+) verapamil, but the elimination half-time ($T_{1/2(\beta)}$) was longer in rat following oral administration of racemic verapamil. At 1.3 h after oral administration of racemic verapamil, however, there were no significant differences between enantiomers for the distributions in major tissues such as heart, cerebrum, cerebellum, liver, spleen and kidney.

• YAKHAK HOEJI
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• v.41 no.3
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• pp.277-282
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• 1997

Methamphetamine, which is the most commonly abused drug in Korea, exists in terms of d-, l- isomers and a racemate(dl). d-Methamphetamine is a potent central nervous system stimulant, whereas l-Methamphetamine is sold freely as a nasal decongestant. In addition, methamphetamine appears in different ratios of optical isomers by the clandestine synthesis applied. In this study, enetiomeric separation of methamphetamines was estabilished to distinguish the chirality of methamphetamines trafficked and abused in Korea. A gas chromatograph/mass spectrometer(GC/MS) system equipped with an achiral capillary column is used to isolate the isomers of methamphetamine after (S)-N-(trifluoroacetyl)-l-prolyl(TFP) deravatization.After analyzing 10 illicit methamphetamine powders and 10 positive urine samples, following findings were found: d-Methamphetamine was well resolved from l-Methamphetamine by chromatographic separation of TFP derivatibes on DB-5 with retention time of 11.80 and 11.35 min respectively. The detection of d-Methamphetamine in all 10 powders and 10 urine samples proves that all methamphetamines abused in Korea are illegally manyfactured and administred.