| 1. |
- Lindholm, Johan, et al.
(författare)
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Use of liquid chromatography-diode-array detection and mass spectrometry for rapid product identification in biotechnological synthesis of a hydroxyprogesterone
- 2003
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Ingår i: Journal of Chromatography A. - 0021-9673 .- 1873-3778. ; 992:1-2, s. 85-100
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Tidskriftsartikel (refereegranskat)abstract
- In exploratory scale biotechnological process development, the product must be rapidly identified although a reference compound may not always be available. LC-diode-array detection and MS were used for this purpose in a process producing 9alpha-hydroxyprogesterone from progesterone as substrate. The electrospray ionization mass spectrometer was combined with an ion trap mass spectrometer for the second generation MS. The preliminary identification, which could be carried out within the course of a day, confirmed that the product was a hydroxyprogesterone. The final identification step, which was much more material intensive and hence time consuming, involved a two-step preparative separation to yield quantities necessary for definitive product identification based on 1H- and 13C NMR.
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| 2. |
- Elhamili, Anisa, et al.
(författare)
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The effect of sample salt additives on capillary electrophoresis analysis of intact proteins using surface modified capillaries.
- 2009
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1216:17, s. 3613-3620
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Tidskriftsartikel (refereegranskat)abstract
- The effect of adding alkali salts to protein samples for capillary electrophoretic (CE) analysis of intact proteins was studied. A high degree of peak stacking, even for large proteins, was found to occur when alkali salts were added to the sample. The addition of salt to the protein sample promotes a strong improvement in the peak efficiency of individual proteins giving up to 2.1 x 10(6) apparent plates/m. The concentration of salt required in the sample to reach optimal peak efficiency show dependency on both the molecular weight and molar concentration of the protein. However, adding salt will, at a sufficiently high concentration, cause a mixture of proteins to co-migrate to one very sharp peak. The observed sample stacking effect was obtained with a number of different surface modified silica capillaries indicating a general phenomenon and not surface coating specific.
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| 3. |
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| 4. |
- Mohabbati, Sheila, et al.
(författare)
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Improved properties of the non-covalent coating with N,N-didodecyl-N, N-dimethylammonium bromide for the separation of basic proteins by capillary electrophoresis with acidic buffers in 25mum capillaries
- 2006
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1121:1, s. 32-39
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Tidskriftsartikel (refereegranskat)abstract
- Capillaries (25 μm I.D.) treated with the double-alkyl-chain cationic surfactant N,N-didodecyl-N, N-dimethylammonium bromide (DDAB) in an improved coating procedure were used for separation of four basic proteins in volatile buffers (ammonium acetate and ammonium hydroxyacetate) as well as in a non-volatile buffer (sodium phosphate) at pH 4. The DDAB coating was stable enough to, without recoating, permit consecutive separations of the proteins up to 9 h with good precisions in peak areas (RSD = 1.1%) and migration times and with high apparent efficiencies (over 1 million theoretical plates/m) in the presence of a strong anodic electroosmosis. Adsorption of the proteins onto the capillary surface, which in previous studies was found to give a certain contribution to zone broadening, was eliminated with the new modified coating method. Complex formation between the proteins and phosphate buffer was studied and confirmed, and it is proposed that slow protein–buffer component interactions are the main contributions to zone broadening in protein separations by CE.
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| 5. |
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| 6. |
- Sundström, Ingela, et al.
(författare)
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Method development for identification of ketobemidone metabolites in microdialysate samples by coupled-column capillary liquid chromatography-tandem mass spectrometry
- 2008
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1189:1-2, s. 503-513
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Tidskriftsartikel (refereegranskat)abstract
- Methodologies for identification of ketobemidone metabolites in microdialysate samples utilizing coupled-column capillary liquid chromatography-electrospray quadrupole time-of-flight tandem mass spectrometry are presented. Two different methods were developed to efficiently analyze the metabolites norketobemidone, ketobemidone N-oxide and hydroxyketobemidone, respectively. Both methods include on-line desalting and trapping of the analytes on micro-solid-phase extraction columns with different retention mechanisms. Norketobemidone and ketobemidone N-oxide were trapped on a C18 column and then eluted by back-flush followed by isocratic separation on a fluorinated reversed-phase type silica gel column (Fluofix). Retention equations are proposed for the chromatographic observations made on the Fluofix column. Hydroxyketobemidone was trapped on a phenylboronic acid column by complex formation at basic pH and then eluted at acidic pH directly into to the mass spectrometer. Oxidation of hydroxyketobemidone to its corresponding quinone was also observed. The methods were successfully used to analyze synthetic ketobemidone metabolites in dilute low-volume microdialysis samples
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