| From Liters to Microliters | ||||||
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Do you ever wonder how much organic solvent is consumed performing continuous LC-MS analyses? At 1–2 mL per minute the volume adds up to liters in rapid fashion. Over time this generates substantial operating and disposal costs. |
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| From Hours to Minutes | ||||||
| Have you been considering how to increase the throughput of LC-MS analyses? In gradient LC, throughput is often a compromise between resolution and speed. Even so, column equilibration and gradient establishment results in an analysis measured in hours. With CE, high resolution separations can be accomplished in only a few minutes. This not only allows you to increase throughput, but allows many experiments to be run in a short period of time, optimizing sample coverage and analyte ionization. |
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| From Undersampling to High Coverage | ||||||
| An inherent problem in protein identification is the low sequence coverage obtained from a complex mixture of peptides. Reasons for this include undersampling, a wide concentration dynamic range, and differing electro-spray ionization efficiency of peptides under each mobile phase composition. A solution to this problem is to use the high speed of CE in a serial injection mode combined with both dynamic ion exclusion algorithms and gas phase fractionation in electro spray-MS/MS. This (CE-MS/MS)n approach increases the coverage of unique peptides that are identified. For example (CE-MS/MS)6 can be achieved in the same time it would take to do a single gradient nano LC-MS/MS run (approximately 1 hour). |
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| CE is a Good Compliment to RPLC | ||||||
| Separations by capillary zone electrophoresis (CZE) are based on differences in an analyte’s mobility (charge/mass) in an electric field and are typically performed in an aqueous medium. These methods are highly selective for analytes which are hydrophilic and highly ionic. These analytes typically do not retain well on RPLC and include compounds such as: • Drug metabolites • Amino acids • Carbohydrates • Natural products As RPLC is based on differences in an analyte’s hydrophobicity, combining data generated from this methodology with data generated by CE often unveils new information. The same/similar buffer conditions can be used for the majority of these compounds with essentially no change-over between sample types. |
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| Resolving and Identifying Positional Isomers | ||||||
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A high resolution separation is required when trying to identify and differentiate positional isomers, as both isomers have the same mass. In the following example CE with laser induced fluorescence (LIF) detection, coupled with mass spectrometry is used to resolve and identify APTS labeled N-linked oligosaccharides released from a commercially available IgG monoclonal antibody. CE-LIF is a highly resolving separation tool while MS/MS provides the characterization and identity. Data courtesy of Etsuo Arai, Beckman Coulter & Daisuke Higo, Bruker Daltonics Japan.
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| Sheath Liquid CE Sprayers | ||||||
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The following highlights the interface of a Beckman Coulter PA 800 Protein Characterization System with the Bruker Daltonics HCT Ultra Ion trap MS/MS. The Bruker interface is equipped with a sheath liquid grounded needle sprayer. The PA 800 system thermostats the capillary using a recirculating liquid coolant, providing highly reproducible separations to the mass spectrometer.
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| CE-MS/MS Usage | ||||||
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Due to the increasing demand for alternative separation technologies many different approaches have been made to achieve robust CE-MS coupling. The demonstration of higher sensitivity detection in CE-MS has fueled an increase in the use of this technology. An increase in the number of protein and metabolite analysis publications further reflects this growing interest.
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