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Dissertation
Quantitative aspects of matrix-assisted laser desorption/ionization using electrospray deposition
Doctor of Philosophy (Ph.D.), Drexel University
Mar 2002
DOI:
https://doi.org/10.17918/00000602
Abstract
MALDI is routinely used as a soft-ionization technique in mass spectrometry for the qualitative analysis of biological and synthetic materials of a wide range of molecular weights. Recently, numerous groups have explored its use as a quantitative technique. The main limitation reported is in the irreproducibility of the collected mass spectra that was attributed to heterogeneity in the final MALDI samples resulting from the traditional air-dried drop method of sample deposition. In this research, the electrospray deposition technique was utilized to quantify proteins of moderate size, including insulin. Various sample cleanup methods were explored, and the use of sample additives (crown ethers) and buffer (ammonium salts) underlayers have shown to reduce the appearance of alkali adducts, yielding good quality MALDI spectra. Improvement of the electrospray deposition process for use in quantitative MALDI has also resulted in a better understanding of the MALDI process itself. Extensive analyses of quantitative mixtures of peptides (DDAVP/AVP) and proteins (bovine and porcine insulin) in a number of different matrices, namely sinapinic acid, ferulic acid, and 2,5-dihydroxybenzoic acid have demonstrated that MALDI is a mass sensitive technique. To maintain analyte signal, matrix concentration must decrease as the analyte concentration decreases. Each analyte studied possesses an optimum matrix-to-analyte ratio for analysis that varies with both analyte size and matrix choice. Analyte signal saturation is also observed and rationalized by experiment as a problem with the desorption rather than the ionization steps in the MALDI process. Problems encountered in the electrospray deposition of volatile MALDI matrices and their implications, and difficulties in the development of a quantitative MALDI method for the determination of insulin in biological sample will be discussed.
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Details
- Title
- Quantitative aspects of matrix-assisted laser desorption/ionization using electrospray deposition
- Creators
- Cynthia M. Chavez-Eng
- Contributors
- Kevin Glenn Owens (Advisor)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xvi, 159 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Arts and Sciences; Chemistry; Drexel University
- Other Identifier
- 991014970203904721