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S Terabe

Publications and source records attributed to S Terabe.

18 recordsLinked to original sources
PubMed1995

Separation of eleven angiotensin II analogs by capillary electrophoresis with a nonionic surfactant in acidic media.

Eleven angiotension II analogs of same chain length were separated by capillary electrophoresis at pH 2.0 with 200 mM Tween 20. All compounds except one pair of angiotensin II ([Sar1, Gly8]- and [Sar1, Val5, Ala8]-angiotensin II) were baseline-separated, even in the case of peptides with about the same total charge. The migration order of the angiotensin II analogs were determined by the hydrophobicity of the amino acid as long as the difference between amino acids of two peptides is the conservative change. From the study of pH dependency of the separation of these peptides, it was found that the conditions of a low electroosmotic flow under a low pH is effective for the separation of similar peptides.

Amino Acid Sequence↗
PubMed1995

Enantiomeric separation of diltiazem, clentiazem, and its related compounds by capillary electrophoresis using polysaccharides.

The direct separation of the enantiomers of diltiazem and its three chloro derivatives, including clentiazem, was investigated by capillary zone electrophoresis (CZE) and electrokinetic chromatography (EKC) using polysaccharides. An electrically neutral beta-cyclodextrin polymer, dextran sulfate, and mucopolysaccharides, such as heparin and chondroitin sulfate C, were employed as chiral selectors. Among the tested solutes, 8-chlorodiltiazem (clentiazem) was well enantiorecognized by the methods. Affinity electrokinetic chromatography (AEKC) using chondroitin sulfate C was the most successful; all tested solutes were completely enantioseparated by this mode.

Calcium Channel Blockers↗
PubMed1992

Separation of closely related large peptides by micellar electrokinetic chromatography with organic modifiers.

Large peptides with similar electrophoretic mobilities were separated by micellar electrokinetic chromatography (MEKC) with organic modifiers. [Leu13]motilin and [Met13]motilin differ by only one neutral amino acid residue. Because the electrophoretic mobilities of these peptides are almost identical, these peptides were not separated by capillary zone electrophoresis (CZE). Such large peptides have not been separated by conventional MEKC either, because they interacted strongly with the micelle. However, they were completely separated by MEKC when an organic solvent was added to the micellar solution. Some insulins, larger peptides than motilin, from different origins, which have very similar electrophoretic mobilities, were also successfully separated by the same technique. The size of peptides which were separated without organic modifiers was examined.

Amino Acid Sequence↗
PubMed1990

Chiral separation of diltiazem, trimetoquinol and related compounds by micellar electrokinetic chromatography with bile salts.

The separation of optically isomeric diltiazem hydrochloride, trimetoquinol hydrochloride and related compounds by micellar electrokinetic chromatography was investigated employing four bile salts as chiral surfactants. The chiral separation of diltiazem hydrochloride and timetoquinol hydrochloride was successfully achieved by use of sodium taurodeoxycholate under neutral conditions, although enantiomers of carboline derivatives A and B and 2,2'-dihydroxy-1,1'-dinaphthyl were resolved with all the bile salts under conditions from neutral to alkaline. The chiral separation of diltiazem-related compounds was affected by the structure of the samples in addition to the effects of bile salt structures and pH of the buffer solutions. Application to the optical purity testing of trimetoquinol hydrochloride by the area percentage method is described. A possible chiral separation mechanism is briefly mentioned.

Bile Acids and Salts↗
PubMed1990

Separation and determination of lipophilic corticosteroids and benzothiazepin analogues by micellar electrokinetic chromatography using bile salts.

The separation of corticosteroids and benzothiazepin analogues by micellar electrokinetic chromatography (micellar EKC) was studied in comparison with capillary zone electrophoresis. The separation of these substances was not successful under neutral and alkaline conditions because they migrated with the same velocity as that of the electroosmotic flow. Micellar EKC with sodium dodecyl sulphate (SDS) solutions was also not successful because these substances migrated with almost the same velocity as that of the SDS micelle, owing to their high lipophilicity. The use of bile salts, which have a similar skeleton to corticosteroids, as the micellar phase permitted the separation of these substances with high theoretical plate numbers (150,000-350,000) within a short time (ca. 15 min). Sodium cholate was particularly useful. The effects of bile salt concentration, pH and the addition of methanol were investigated. Micellar EKC was also applied to the determination of the drug substances in tablets and cream using the internal standard method and to purity testing of drug substances and tablets.

Adrenal Cortex Hormones↗
PubMed1990

Separation and determination of the ingredients of a cold medicine by micellar electrokinetic chromatography with bile salts.

The separation of fourteen active ingredients used in a cold medicine was investigated by micellar electrokinetic chromatography (EKC) employing bile salts. Basic drugs were also successfully separated by micellar EKC using bile salts with high theoretical plate numbers (2.0 x 10(5)-3.5 x 10(5)) within a relatively short time (ca. 20 min). The separation of these solutes by micellar EKC was not successful using sodium dodecyl sulphate. The effects of micellar concentration, pH and organic modifier content on migration times and selectivity were investigated. This technique was also applied to the determination of several active ingredients combined in commercial preparations by an internal standard method.

Acetaminophen↗
PubMed1990

Application of micellar electrokinetic chromatography to pharmaceutical analysis.

Electrokinetic chromatography is a new type of analytical separation method which belongs to the group of high performance capillary electrophoretic techniques but whose separation principle is based on that of chromatography. The solute distributes itself between a carrier and the surrounding medium. The carrier, which corresponds to the stationary phase in conventional chromatography, can be transported by electrophoresis with a different velocity from the surrounding medium. The separation is achieved by the differential solute distribution and the differential migration of the carrier. The charged molecules or charged molecular aggregates are employed as the carrier. Various kinds of carriers are available for electrokinetic chromatography along with different partition mechanisms. Among them, micellar electrokinetic chromatography, which employs an ionic micelle as a carrier, has become the most popular method because of its unique and attractive characteristics as well as the separating capability of electrically neutral or nonionic solutes in comparison with capillary zone electrophoresis. The present paper describes the principle, separation characteristics and its application to the analysis of pharmaceuticals.

Chromatography↗
PubMed1990

Effects of methanol and urea on optical resolution of phenylthiohydantoin-DL-amino acids by micellar electrokinetic chromatography with sodium N-dodecanoyl-L-valinate.

Effects of methanol and urea on enantiomeric resolution of phenylthiohydantoin (PTH)-DL-amino acids by micellar electrokinetic chromatography with sodium N-dodecanoyl-L-valinate (SDVal) were investigated. PTH-DL-Met that could not be optically resolved with an SDVal solution alone was resolved by using an SDVal/methanol solution. Four PTH-DL-amino acids were separated from each other and each pair of enantiomers was also optically resolved, although seriously tailed peaks were observed for each solute. The addition of urea to SDVal/methanol solutions improved these peak shapes.

Amino Acids↗
PubMed1990

Effect of surfactant structures on the separation of cold medicine ingredients by micellar electrokinetic chromatography.

Using micellar electrokinetic chromatography (micellar EKC or MEKC) the retention behavior of twelve active ingredients used in cold medicines was investigated. The role of five different anionic surfactants was investigated by MEKC and the results were compared with those obtained by conventional capillary zone electrophoresis (CZE). The relative retention order of the 12 ingredients was significantly different among the five surfactants; the different elution orders were ascribed to the differences in the hydrophilic groups of the surfactants. The effects of surfactant concentration and buffer pH were also investigated. The ingredients were successfully separated within 30 min by micellar EKC with high theoretical plate numbers (approximately 200,000), and selectivity was much improved in comparison with CZE. Micellar EKC was applied by the internal standard method to the quantitation of some active ingredients combined in commercial preparations.

Chemical Phenomena↗
PubMed1989

Separation of beta-lactam antibiotics by micellar electrokinetic chromatography.

The retention behaviour of beta-lactam antibiotics in micellar electrokinetic chromatography (EKC) was investigated. Sodium dodecyl sulphate (SDS) and sodium N-lauroyl-N-methyltaurate were used an anionic surfactants at concentrations of 0.05-0.3 M. It was found that the retention of ionic substances in micellar EKC is determined by the following three factors: the electrophoretic migration of the ionic substances, the interaction between the ionic substances and ionic surfactants and solubilization of the solute by the micellar phase. A difference in the retention behaviours of cationic substances was observed between the two anionic surfactants, which have different groups neighbouring the charge-bearing groups. The effect of an ion-pairing reagent was also investigated to make the effect of the micelle clearer. All test solutes were successfully separated by micellar EKC at SDS concentrations above 0.1 M, with theoretical plate numbers ranging from 70,000 to 260,000.

Anti-Bacterial Agents↗
PubMed1989

Separation of water-soluble vitamins by micellar electrokinetic chromatography.

The retention behaviour of eleven water-soluble vitamins in micellar electrokinetic chromatography (micellar EKC) was investigated in comparison with capillary zone electrophoresis. Sodium dodecyl sulphate (SDS) and sodium lauroylmethyl taurate were used as the anionic surfactants at concentrations of 0.05-0.2 M in micellar EKC. The retention times of cationic substances increased more rapidly with increasing concentration of the anionic surfactant than those of other substances. This result suggests that ion-pair formation between cationic substances and anionic surfactants contributes to the retention of the former. The difference in the structures of the two surfactants affects the retention behaviour of solutes, especially cationic substances. To clarify the effect of the micelle, an ion-pairing agent that does not form the micelle structure was employed. All solutes were successfully separated within 15 min by using a 650 mm x 0.05 mm I.D. fused-silica tube with a 0.05 M SDS solution (pH 9.0) to give theoretical plates ranging from 100,000 to 350,000.

Chemical Phenomena↗
PubMed1981

Separation of cytochromes c by reversed-phase high-performance liquid chromatography.

Six kinds of cytochrome c of different origin, i.e., bovine, chicken, dog, horse, rabbit and tuna, were subjected to separation by reversed-phase high-performance liquid chromatography on three commercial packing materials; octadecyl-, octyl- and cyanoalkyl-silicas. The effects of reversed-phase material, mobile phase and temperature on the separation of cytochromes c were examined. The parameters of the mobile phase were the organic modifier, the pH, the salt concentration and additives. Under optimal conditions, five of the six cytochromes c were resolved in 10 min. The relative retention values cannot be explained in terms of the relative lipophilicities of the side-chains of the amino acid residues.

Animals↗
PubMed1979

Separation of some polypeptide hormones by high-performance liquid chromatography.

Twenty-one analogues of ACTH, three analogues of LH-RH and four insulins have been successfully separated on a commercial reversed-phase material with tartrate buffer--acetonitrile systems containing sodium 1-butanesulphonate and sodium sulphate as the mobile phase. The effect of the constituent amino acid residues on the order of elution has been studied in detail by using a variety of closely related peptides; the order of elution of a series of peptides, which differ by only one amino acid residue, can in most instances be explained in terms of the difference in the hydrophobicities of the amino acid residues concerned, but in some instances, such as in diastereoisomers or positional isomers, the order of elution must be interpreted in terms of the hydrophobicity of the whole peptide molecule. This chromatographic method has been proved to be very useful for the rapid examination of the purity of these peptide hormones and for the separation of closely related peptides with molecular weights up to ca. 6000.

Adrenocorticotropic Hormone↗
PubMed1979

Resolution of peptide antibiotics, cerexins and tridecaptins, by high performance liquid chromatography (studies on antibiotics from the genus Bacillus. XXVI).

By high performance liquid chromatography, cerexin B was separated into four components (B1, B2, B3 and B4), cerexin D into four components (D1, D2, D3 and D4), tridecaptin A into components (A alpha and A beta), tridecaptin B into four components (B alpha, B beta, B gamma and B delta) and tridecaptin C into three components (C alpha 1, C alpha 2 and C beta 1). All components were preparatively isolated, and their fatty acid and amino acid compositions determined for structural elucidation.

Amino Acid Sequence↗
PubMedDate not supplied

Selectivity manipulation in micellar electrokinetic chromatography.

Micellar electrokinetic chromatography (MEKC) permits the separation of electrically neutral analytes by chromatographic principles in a capillary electrophoresis system. The most effective way to obtain high resolution in MEKC is to increase the separation factor, as in conventional chromatography. The separation factor in MEKC depends on the molecular structure of the micelle and hence on the surfactant used, the pH of solution, and the nature of any additives to the micellar solution. The hydrophilic moieties of surfactant molecules generally affect selectivity more than do the hydrophobic moieties. Chiral surfactants enable the enantiomeric separation of mixtures of chiral solutes to be achieved. Mixed micelles consisting of ionic and nonionic surfactants display different selectivity from that of single ionic micelles. Additives such as cyclodextrins, ion-pair reagents, urea, organic solvents and metals can also serve as useful modifiers of the micellar solution for improving separation. In particular, cyclodextrins are useful for the separation of aromatic isomers and enantiomers. A general introductory guide to the design of successful separations by MEKC is proposed, based primarily on the author's work.

Cyclodextrins↗