Pub Date : 2019-01-01DOI: 10.2174/2213240606666190709100858
Igor G Zenkevich, Nino G Todua, Anzor I Mikaia
Background: Application of simple regularities and general principles along with direct use of reference gas chromatography retention index data for reliable structure determination of compounds can be enhanced by determination of new regularities that are specific to certain structural elements.
Objective: Revelation and interpretation of an anomaly in the elution order of alkyl esters of alkoxycarbonyl derivatives of glycine and alanine on standard and semi-standard non-polar phases.
Method: Preliminary derivatization of amino acids to alkyl esters of N-alkoxycarbonyl analogs and interpretation of their gas chromatographic characteristics.
Results: Alkyl esters of N-alkoxycarbonyl derivatives of alanine (Alkyl = C2H5, n- and iso-C3H7) elute prior to the same derivatives of glycine, despite the presence of an additional methyl group at C(2) in the molecule. Elution order is reversed for methyl esters of N-methoxycarbonyl derivatives.
Conclusion: It is established that the peculiar behavior of alkyl esters of N-alkoxycarbonyl derivatives of glycine and alanine agrees with the concepts of gas chromatography and the known retention index regularities of organic compounds. A decrease of retention index values is a result of an introduction of an additional methyl group to a carbon atom connected to two polar fragments in a molecule like CH2XY. The dependence of the difference of retention index values for homologs of the types of CH3-CHXY and CH2XY vs. the total mass of fragments (X + Y) is similar to those for other sub-groups of analytes.
{"title":"Unusual Regularity in GC Retention of Simple Amino Acid Derivatives.","authors":"Igor G Zenkevich, Nino G Todua, Anzor I Mikaia","doi":"10.2174/2213240606666190709100858","DOIUrl":"10.2174/2213240606666190709100858","url":null,"abstract":"<p><strong>Background: </strong>Application of simple regularities and general principles along with direct use of reference gas chromatography retention index data for reliable structure determination of compounds can be enhanced by determination of new regularities that are specific to certain structural elements.</p><p><strong>Objective: </strong>Revelation and interpretation of an anomaly in the elution order of alkyl esters of alkoxycarbonyl derivatives of glycine and alanine on standard and semi-standard non-polar phases.</p><p><strong>Method: </strong>Preliminary derivatization of amino acids to alkyl esters of N-alkoxycarbonyl analogs and interpretation of their gas chromatographic characteristics.</p><p><strong>Results: </strong>Alkyl esters of N-alkoxycarbonyl derivatives of alanine (Alkyl = C<sub>2</sub>H<sub>5</sub>, <i>n</i>- and <i>iso</i>-C<sub>3</sub>H<sub>7</sub>) elute prior to the same derivatives of glycine, despite the presence of an additional methyl group at C<sup>(2)</sup> in the molecule. Elution order is reversed for methyl esters of N-methoxycarbonyl derivatives.</p><p><strong>Conclusion: </strong>It is established that the peculiar behavior of alkyl esters of N-alkoxycarbonyl derivatives of glycine and alanine agrees with the concepts of gas chromatography and the known retention index regularities of organic compounds. A decrease of retention index values is a result of an introduction of an additional methyl group to a carbon atom connected to two polar fragments in a molecule like CH<sub>2</sub>XY. The dependence of the difference of retention index values for homologs of the types of CH<sub>3</sub>-CHXY and CH<sub>2</sub>XY <i>vs</i>. the total mass of fragments (X + Y) is similar to those for other sub-groups of analytes.</p>","PeriodicalId":10826,"journal":{"name":"Current chromatography","volume":"2000 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6774356/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82798268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.2174/22132406113099990001
Ying Ma, Yoichiro Ito
In conventional high-performance liquid chromatography, chiral separations are performed by chiral column with a chiral selector (CS) chemically boned to the solid support. In contrast, high-speed counter-current chromatography (HSCCC) performs chiral separations by dissolving CS in the liquid stationary phase. During the past two decades, several CSs were developed to successfully carry out chiral HSCCC which include N-dodecanoyl-L-proline-3,5-dimethylanilide, β-cyclodextrin derivatives, vancomycin, cinchona alkaloid derivatives, cellulose and amylose derivatives, tartaric acid derivatives, etc. Compared to HPLC which uses over hundred different kinds of CSs, the number of CSs effectively used in HSCCC is limited to several compounds. This may be due to the violent molecular movement of CS dissolved in the liquid stationary phase which reduces chiral selectivity based on steric affinity. Future development strategy of CS for HSCC proposed here is to suppress the molecular movement of the CS in the liquid stationary phase by the following three ways: 1) using viscous stationary phase such as aqueous-aqueous polymer phase system; 2) attaching a long hydrophobic chain to the asymmetric carbon, or 3) chemically bonding CS onto hydrophobic small particles such as carbon nanotubes, gold colloidal particles, and submicron silica particles.
{"title":"Chiral High-Speed Counter-Current Chromatography: Future Strategies for Chiral Selector Development.","authors":"Ying Ma, Yoichiro Ito","doi":"10.2174/22132406113099990001","DOIUrl":"10.2174/22132406113099990001","url":null,"abstract":"<p><p>In conventional high-performance liquid chromatography, chiral separations are performed by chiral column with a chiral selector (CS) chemically boned to the solid support. In contrast, high-speed counter-current chromatography (HSCCC) performs chiral separations by dissolving CS in the liquid stationary phase. During the past two decades, several CSs were developed to successfully carry out chiral HSCCC which include N-dodecanoyl-L-proline-3,5-dimethylanilide, β-cyclodextrin derivatives, vancomycin, cinchona alkaloid derivatives, cellulose and amylose derivatives, tartaric acid derivatives, etc. Compared to HPLC which uses over hundred different kinds of CSs, the number of CSs effectively used in HSCCC is limited to several compounds. This may be due to the violent molecular movement of CS dissolved in the liquid stationary phase which reduces chiral selectivity based on steric affinity. Future development strategy of CS for HSCC proposed here is to suppress the molecular movement of the CS in the liquid stationary phase by the following three ways: 1) using viscous stationary phase such as aqueous-aqueous polymer phase system; 2) attaching a long hydrophobic chain to the asymmetric carbon, or 3) chemically bonding CS onto hydrophobic small particles such as carbon nanotubes, gold colloidal particles, and submicron silica particles.</p>","PeriodicalId":10826,"journal":{"name":"Current chromatography","volume":"1 1","pages":"69-80"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3943172/pdf/nihms487506.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40294648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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