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- Elhamili, Anisa
(författare)
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Development of Capillary Electrophoresis Methods Coupled to Mass Spectrometry for Biomedical and Pharmaceutical Analysis
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The analysis of large intact proteins and complex biological samples containing drug molecules is a common complicated task for many scientists. However, due to the importance of these molecules, there is a growing interest in pharmaceutical and medicinal research to develop rapid, highly sensitive and efficient analytical techniques. The advantages of capillary electrophoresis (CE) in combination with mass spectrometry (MS) provide a powerful analytical tool. However, further improvement and development of these techniques are required to extend their utility and to meet the challenges of selected analytes. Thus, the scope of this thesis deals with the development of novel analytical methods to achieve efficient and high performance analysis of peptides, intact proteins, digests of complex samples and basic pharmaceutical drug compounds in biological matrices. Implementation of CE for routine analysis of proteins and complex samples is constrained by the partial adsorption to the capillary wall. Consequently, the use of surface modified capillaries is required to control the surface properties and prevent analyte adsorption. In this thesis, analyte adsorption was successfully prevented using tailored covalent cationic (M7C4I) and electrostatic cationic (PVPy-Me) coatings. Rapid and efficient separations of peptides, proteins and digests of complex samples such as cerebrospinal fluids were obtained with these coatings. The M7C4I coating showed a distinct ability to handle large intact proteins with a molecular size of over 0.5 MDa. The highest peak efficiencies and surprisingly high peak stacking effects were obtained by adding salts to the protein samples. The effect of salt additives on peak efficiencies of intact proteins was further demonstrated and compared using different surface modified capillaries. Additionally, rapid CE-ESI-MS quantification of pharmaceutical drug molecules in human plasma was performed after a SCX-SPE sample preparation method using the M7C4I coating. In conclusion, the results presented in this thesis show the strong potential of CE in combination with MS using electrospray ionization (ESI) for the analysis of peptides and large intact proteins and the applicability for clinical monitoring of the levels of pharmaceutical drug molecules in human plasma with high sensitivity and efficiency.
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- 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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- Fornstedt, Torgny, 1957-, et al.
(författare)
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System peaks and their impact in liquid chromatography
- 2016
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Ingår i: TrAC. Trends in analytical chemistry. - : Elsevier. - 0165-9936 .- 1879-3142. ; 81, s. 42-50
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Forskningsöversikt (refereegranskat)abstract
- A sample injected into a chromatographic system can generate extra peaks, called "system peaks", which in general are undetectable. However, for small analytical injections, solute zones eluting with a system zone will often give strongly deformed solute peaks. But, if a solute zone is eluted in a particular region of the system zone it will instead be strongly compressed and well-shaped. For overloaded solute injections, another type of complex band deformation may take place due to large system peaks. This review will present results related to system peak distortions of both small analytical peaks and large preparative ones. Guidelines will be given on how to avoid unwanted distortions and how to utilize the distortions for increased detectability in analytical chromatography, or enhanced production rate in preparative chromatography. The works reviewed here were mainly made by Georges Guiochon, and some of his close colleagues, and is dedicated to his memory.
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- Gordi, Toufigh, et al.
(författare)
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Direct analysis of artemisinin in plasma and saliva using coupled-column high-performance liquid chromatography with a restricted-access material pre-column
- 2000
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Ingår i: Journal of Chromatography B. - 1387-2273 .- 1878-5603. ; 742:1, s. 155-162
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Tidskriftsartikel (refereegranskat)abstract
- A previously established HPLC system with post-column derivatization for the analysis of artemisinin was coupled to an ADS (alkyl-diol silica) pre-column, allowing direct and repetitive injection of protein-rich fluids such as plasma. The limit of quantitation for 100 μl of plasma was 10 ng/ml (CV=10.5%) while concentrations down to 2 ng/ml could be quantified for 1.00 ml saliva samples (CV=11.1%). The system was linear in the tested range of 10–2000 ng/ml for plasma and 2–240 ng/ml for saliva samples, respectively. This paper introduces coupled column HPLC as a simplified method for the routine analysis of artemisinin in biological fluids.
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- Harang, Valérie, et al.
(författare)
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A statistical experimental design to study factors affecting enantioseparation of propranolol by capillary electrophoresis with cellobiohydrolase (Cel7A) as chiral selector.
- 2002
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Ingår i: Electrophoresis. - 0173-0835 .- 1522-2683. ; 23:14, s. 2306-2319
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Tidskriftsartikel (refereegranskat)abstract
- The capillary electrophoretic enantioseparation of rac-propranolol using cellobiohydrolase Tr Cel7A as selector was optimized by an unbiased statistical experimental design. A set of pre-experiments was performed in order to identify critical experimental factors. In the definitive chemometric design pH, ranging from 5 to 7, ionic strength ranging between 0.01 and 0.02 and organic solvent additive in concentration from 1 to 19% v/v were studied. The response surface plot revealed a separation optimum in the pH interval studied. When all parameters were taken into account, a background electrolyte consisting of 0.016 M bistris-acetate buffer with pH 6.5 and 17% v/v acetonitrile gave the optimum separation. The significance of the statistical design was confirmed by the generally good agreement obtained between predicted response and actual experimental data.
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- Harang, Valérie, 1966-
(författare)
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Aspects of Optimisation of Separation of Drugs by Chemometrics
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Statistical experimental designs have been used for method development and optimisation of separation. Two reversed phase HPLC methods were optimised. Parameters such as the pH, the amount of tetrabutylammonium (TBA; co-ion) and the gradient slope (acetonitrile) were investigated and optimised for separation of erythromycin A and eight related compounds. In the second method, a statistical experimental design was used, where the amounts of acetonitrile and octane sulphonate (OSA; counter ion) and the buffer concentration were studied, and generation of an α-plot with chromatogram simulations optimised the separation of six analytes.The partial filling technique was used in capillary electrophoresis to introduce the chiral selector Cel7A. The effect of the pH, the ionic strength and the amount of acetonitrile on the separation and the peak shape of R- and S-propranolol were investigated.Microemulsion electrokinetic chromatography (MEEKC) is a technique similar to micellar electrokinetic chromatography (MEKC), except that the microemulsion has a core of tiny droplets of oil inside the micelles. A large number of factors can be varied when using this technique. A screening design using the amounts of sodium dodecyl sulphate (SDS), Brij 35, 1-butanol and 2-propanol, the buffer concentration and the temperature as factors revealed that the amounts of SDS and 2-propanol were the most important factors for migration time and selectivity manipulation of eight different compounds varying in charge and hydrophobicity. SDS and 2-propanol in the MEEKC method were further investigated in a three-level full factorial design analysing 29 different compounds sorted into five different groups. Different optimisation strategies were evaluated such as generating response surface plots of the selectivity/resolution of the most critical pair of peaks, employing chromatographic functions, simplex optimisation in MODDE and 3D resolution maps in DryLab™.Molecular descriptors were fitted in a PLS model to retention data from the three-level full factorial design of the MEEKC system. Two different test sets were used to study the predictive ability of the training set. It was concluded that 86 – 89% of the retention data could be predicted correctly for new molecules (80 – 120% of the experimental values) with different settings of SDS and 2-propanol.Statistical experimental designs and chemometrics are valuable tools for the development and optimisation of analytical methods. The same chemometric strategies can be employed for all types of separation techniques.
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