| 1. |
- Fredriksson, Mattias, et al.
(författare)
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A component tracking algorithm for accelerated and improved liquid chromatography-mass spectrometry method development
- 2010
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1217:52, s. 8195-8204
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Tidskriftsartikel (refereegranskat)abstract
- A method for tracking of sample components during liquid chromatography–mass spectrometry (LC–MS) method development has been proposed. The method manages to, fully automatically and without user intervention, find the chromatographic peaks in the data sets, discriminate them to sample components and track them when the separation conditions have been changed. The algorithm utilises the resolution obtained from all considered data sets and has the ability to discriminate the non informative parts. The technique has a great sensitivity even in cases where a majority of the tracked components cannot easily be spotted by means of traditional total ion chromatogram (TIC) or base peak chromatogram (BPC) representations. The method was tested on an experimental sample using six different columns and an average of 79% of the suggested sample components could be successfully tracked at a minimum area of 0.05% of the main component in the sample. 66 components with 79–92% of the total suggested component area were able to be tracked between all data sets. The method could be used to rapidly investigate selectivity during different types of separation conditions.
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| 2. |
- Fredriksson, Mattias, et al.
(författare)
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An objective comparison of pre-processing methods for enhancement of liquid chromatography-mass spectrometry data
- 2007
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1172:2, s. 135-150
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Tidskriftsartikel (refereegranskat)abstract
- Four data pre-processing methods have been applied with different settings to data sets obtained from the analysis of a pharmaceutical drug and its degradation products by liquid chromatography�mass spectrometry (LC�MS). The methods compared were the frequently used component detection algorithm (CODA) and three kinds of digital filters�matched filtration (MF), Gaussian second derivative (GSD) and Savitzky�Golay. The aim was to evaluate the performance and robustness of these methods for extracted ion chromatogram (XIC), total ion chromatogram (TIC) and base peak chromatogram (BPC) in the presence of different types of noise. In accordance with theory, the best improvements in signal-to-noise ratio (S/N) of the XICs were obtained with MF under the ideal case with random white noise. However, when highly coloured noise was present, it was found that no improvements in XIC S/N could be obtained with any of the pre-processing methods studied. GSD and CODA did, however, improve the S/N for both TIC and BPC. GSD and CODA also significantly reduced the background in the spectral domain, thereby facilitating the interpretation of the mass spectra. Another advantage associated with CODA and to some extent also with GSD is their data reduction ability.
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| 3. |
- Petersson, Patrik, et al.
(författare)
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Why ultra high performance liquid chromatography produces more tailing peaks than high performance liquid chromatography, why it does not matter and how it can be addressed
- 2011
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Ingår i: Journal of chromatography. B. - : Elsevier BV. - 1570-0232 .- 1873-376X .- 0021-9673 .- 1873-3778. ; 1218:39, s. 6914-6921
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study is to demonstrate, with experiments and with computer simulations based on a firm chromatographic theory, that the wide spread perception of that the United States Pharmacopeia tailing factor must be lower than 2 (Tf < 2) is questionable when using the latest generation of LC equipment. It is shown that highly efficient LC separations like those obtained with sub-2 μm porous and 2.7 μm superficially porous particles (UHPLC) produce significantly higher Tf-values than the corresponding separation based on 3 μm porous particles (HPLC) when the same amount of sample is injected. Still UHPLC separations provide a better resolution to adjacent peaks. Expressions have been derived that describe how the Tf-value changes with particle size or number of theoretical plates. Expressions have also been derived that can be used to scale the injection volume based on particle size or number of theoretical plates to maintain the Tf-value when translating a HPLC separation to the corresponding UHPLC separation. An aspect that has been ignored in previous publications. Finally, data obtained from columns with different age/condition indicate that Tf-values should be complemented by a peak width measure to provide a more objective quality measure.
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| 4. |
- Spégel, Peter, et al.
(författare)
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Continuous full filling capillary electrochromatography: Nanoparticle synthesis and evaluation
- 2007
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1154:1-2, s. 379-385
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Tidskriftsartikel (refereegranskat)abstract
- Reversed phase continuous full filling capillary electrochromatography with electrospray ionisation mass spectrometric detection was performed with highly sulphated poly [styrene-co-(lauryl methacrylate)-co-(divinylbenzene)] nanoparticles. The nanoparticles that contained a hydrophobic core and a hydrophilic surface were prepared in a one step synthesis using soap free emulsion polymerisation. By changing the concentration of monomers, the polymerisation temperature, and the polarity of the dispersive phase, the size of the nanoparticles could be controlled. With the optimised conditions, nanoparticles with an average size of 157 nm were obtained. These nanoparticles were dispersed in the background electrolyte and used for reversed phase continuous full filling. An orthogonal electrospray ionisation interface was used to separate the eluting nanoparticles from the eluting analytes prior to mass spectrometry detection. Compared to previous studies on reversed phase continuous full filling, the retention, the separation efficiency, and the resolution of a homologous series of dialkyl phthalates were greatly improved.
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| 5. |
- Viberg, Peter, et al.
(författare)
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Continuous full filling capillary electrochromatography: Chromatographic performance and reproducibility
- 2007
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1154:1-2, s. 386-389
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Tidskriftsartikel (refereegranskat)abstract
- Continuous full filling capillary electrochromatography with nanoparticles as pseudostationary phase interfaced with electrospray ionisation mass spectrometric detection was used for reversed phase separations with very high separation efficiency. Several batches of nanoparticles were synthesised and their electrochromatographic performance were evaluated. Different parameters, such as repeatability, reproducibility, limit of detection, and peak asymmetry, were investigated yielding excellent results. The stability of the system over wide pH ranges and over time was found to be excellent. Very high separation efficiencies with over 1.1 million theoretical plates per metre were obtained. The limit of detection for the investigated dialkyl phthalates was approximately 1.0 mu mol L-1, corresponding to 3-5 fmol injected. After preparation, nanoparticle suspensions could be used without further treatment for at least an entire working day with maintained chromatographic qualities. (c) 2007 Elsevier B.V. All rights reserved.
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| 6. |
- Zhang, Yuan, et al.
(författare)
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Critical comparison of performances of superficially porous particles and sub-2 mu m particles under optimized ultra-high pressure conditions
- 2009
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1216:21, s. 4597-4605
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Tidskriftsartikel (refereegranskat)abstract
- The performance of 2.7 mu m superficially porous particles at 600 bar and sub-2 mu m fully porous particles at 1000 bar were compared by the Poppe plot method. Theoretical Poppe plots were first constructed for each stationary phase to compare their kinetic performance at different analysis times. The theory was then verified by experiments under the optimized conditions identified from the Poppe plot calculation. We found that the 2.7 mu m superficially porous particles at 600 bar can provide similar performance compared to the sub-2 mu m fully porous particles at ultra-high pressure (1000bar)when analysis times are very short (e.g. sub-minute). As analysis time increases, the superficially porous particles start to outperform the sub-2 mu m particles and can give much higher efficiencies (e.g. > 2 times higher plate Count) at very long analysis times (>3 h). The comparison was extended to gradient elution of a mixture of pharmaceutical interest by constructing gradient peak capacity Poppe plots and similar behavior was observed. (C) 2009 Elsevier B.V. All rights reserved.
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