Advances in Chromatography最新文献_第6页

Advances in aerosol-based detectors. 气溶胶探测器的进展。

4区化学

Advances in Chromatography Pub Date : 2014-01-01 DOI: 10.1201/b16668-2

Ryan D Cohen, Yong Liu

引用次数: 5

Thin Layer Chromatography with a Controlled Gas Phase Influencing on the Separation. 控制气相薄层色谱法对分离的影响。

4区化学

Advances in Chromatography Pub Date : 2014-01-01 DOI: 10.1201/b15308-8

V. Berezkin, S. Shtykov, E. G. Sumina

引用次数: 0

Chromatographic Separation and NMR An Integrated Approach in Pharmaceutical Development. 色谱分离与核磁共振:药物开发的综合方法。

4区化学

Advances in Chromatography Pub Date : 2012-01-01

Nina C Gonnella

{"title":"Chromatographic Separation and NMR An Integrated Approach in Pharmaceutical Development.","authors":"Nina C Gonnella","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>Over the past 10 years, major improvements in the performance of LC-NMR have been realized. The addition of postcolumn SPE, advances in probe technology including cryogenic probes and microcoil probes, improved solvent suppression pulse sequences, and shielded magnets with better homogeneity have all contributed to rapid advancements in this technology. Application of LC-NMR to problems in pharmaceutical development has had a major impact on structure elucidation studies. LC-NMR has been successfully applied to determine the structures of degradation products, impurities, mixtures of compounds, and metabolites. Use of stop flow techniques with LC-NMR experiments has been a critical means of identifying unstable compounds and studying conformational kinetics. The integration of SPE as an intermediate step between the LC unit and the NMR spectrometer has vastly improved the power of the hyphenated technique in trace analysis applications. Online postcolumn enrichment of chromatographic peaks by SPE dramatically reduces the NMR acquisition times by allowing repeated injections to be trapped onto the same cartridge or different cartridges. Because protonated solvents can be easily removed with a drying procedure, solvents and buffers may be freely chosen for maximizing chromatographic separation without compromising NMR spectral quality. The compound of interest may then be eluted from an SPE cartridge using deuterated organic solvent, which helps to reduce dynamic range issues. When combined with cryogenically cooled microcapillary probes, the sensitivity of the NMR signal increases about 10-fold over conventional room temperature probes, enabling full structure characterization at the microgram level. Heteronuclear experiments with concentrations previously only possible in a limited number of cases have now become standard experiments. The availability of HSQC and HMBC experiments and microcoil/cryogenic technology opens the possibility of using LC-(SPE) NMR for the structural elucidation of complete unknowns on a microgram scale. To enable significant future downscaling beyond the current capabilities, improved performance of the LC-NMR interface and improved SPE cartridge retention need to be addressed. In addition, the active volume of the NMR flow cell or capillary tube will have to shrink along with the corresponding detection coils in order not to lose filling factor. As the size of the NMR probes become more efficient with respect to mass sensitivity, techniques such as CE or capillary electrochromatography (CEC) may be interfaced more successfully with NMR spectroscopy. Overall, the current state of the art in LC-NMR has demonstrated proven utility in a variety of applications. When combined with SPE and cryotechnology, LC-NMR has become an extremely valuable tool for mass limited samples, enabling structure elucidation without the need for laborious serial isolation and purification procedures.</p>","PeriodicalId":50873,"journal":{"name":"Advances in Chromatography","volume":"50 ","pages":"93-138"},"PeriodicalIF":0.0,"publicationDate":"2012-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34062386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The Hydrophobic-Subtraction Model of Reversed-Phase Column Selectivity. 反相柱选择性的疏水-减法模型。

4区化学

Advances in Chromatography Pub Date : 2012-01-01 DOI: 10.1201/b11636-8

Lloyd R Snyder, John W Dolan, Daniel H Marchand, Peter W Carr

引用次数: 32

Organic Monolith Column Technology for Capillary Liquid Chromatography. 毛细管液相色谱有机整体柱技术。

4区化学

Advances in Chromatography Pub Date : 2012-01-01 DOI: 10.1201/b11636-6

Yuanyuan Li, Pankaj Aggarwal, H Dennis Tolley, Milton L Lee

引用次数: 4

Chromatographic Hydrophobicity Index (CHI). 色谱疏水性指数。