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µ-trap for the SALDI-MS screening of organic compounds prior to LC/MS analysis
Stockholm University, Faculty of Science, Department of Analytical Chemistry.
Stockholm University, Faculty of Science, Department of Analytical Chemistry.
Stockholm University, Faculty of Science, Department of Analytical Chemistry.
Stockholm University, Faculty of Science, Department of Analytical Chemistry.
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2008 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 80, no 14, 5515-5523 p.Article in journal (Refereed) Published
Abstract [en]

A procedure for rapidly screening and quantitatively analyzing organic molecules is presented, in which a miniaturized solid-phase extraction (SPE) cartridge containing 0.6 mg of graphitized carbon black (the GCB-mu-trap) is used for sample pretreatment. Then surface-assisted laser desorption ionization dine-of-flight mass spectrometry (SALDI-TOF-MS) screening is followed by liquid chromatography/mass spectrometry (LC/MS) for robust quantitative analysis of samples containing analytes of interest. Liquid samples with volumes up to 100 mL were extracted using the GCB-mu-trap, and SALDI screening was performed by transferring a few particles of the GCB 4 sorbent from the mu-trap onto a stainless steel plate. Analytes were then simply ionized and desorbed by irradiating the GCB 4 particles without any further pretreatment. GCB 4 was found to be an excellent surface for the SALDI analysis of small molecules, providing spectra with very clean backgrounds. The small size of the cartridge (micropipet filter tip) results in enrichment of the analytes on a small surface area, affording low SALDI-TOF-MS detection limits. Furthermore, the removal of just a few particles from the p-trap does not significantly affect the subsequent quantitative determination. This approach offers considerable reductions in analytical costs by eliminating unnecessary SPE-LC/MS analyses.

Place, publisher, year, edition, pages
ACS , 2008. Vol. 80, no 14, 5515-5523 p.
National Category
Analytical Chemistry
Identifiers
URN: urn:nbn:se:su:diva-17512DOI: 10.1021/ac8005186ISI: 000257598100033OAI: oai:DiVA.org:su-17512DiVA: diva2:184033
Available from: 2009-01-16 Created: 2009-01-16 Last updated: 2010-04-22Bibliographically approved
In thesis
1. Novel clean-up, concentration and laser desorption/ionization strategies for mass spectrometry
Open this publication in new window or tab >>Novel clean-up, concentration and laser desorption/ionization strategies for mass spectrometry
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Despite valuable advantages of mass spectrometry (MS) techniques they still have drawbacks that need to be overcome, notably their sensitivity to various kinds of interfering substances and associated difficulties involved in detecting signals from analytes present in trace quantities. Thus, high quality analytical data could be acquired by improving sample pre-treatment techniques and/or ionization methods to increase ionization yields and/or avoid the generation of unwanted ions.

In the studies this thesis is based upon, a microfluidic electrocapture system capable of trapping charged proteins/polypeptides while non-charged species such as non-ionic detergents are swept out, was used to decrease the concentration of detergent in samples containing soluble and membrane associated proteins/polypeptide. Subsequent mass spectrometric analysis yielded well-resolved mass spectra of the target analytes.

In addition, it was found that solid phase extraction (SPE) sorbents such as graphitized carbon black (GCB), can efficiently assist the laser desorption ionization of small molecules without generating any interfering ions which inspired the fabrication of μ-traps and discs. Other matrix-free approaches demonstrated the utility of silicon nitride and oxidized GCB nanoparticles as versatile media for surface-assisted laser desorption ionization (SALDI) of small molecules.

In this thesis it is discussed that small molecule analytes such as Polyphenols present in red wine and quaternary protoberberine alkaloids with highly conjugated systems and acidic/permanently charged functional groups can be readily analyzed without any matrix or assisting-surface.

In summary, the microfluidic electrocapture, new laser desorption ionization methods and surfaces, as well as integrated SALDI and SPE platforms, introduced in this work extend the MS strategies allowing coverage of a wider range of samples.

Place, publisher, year, edition, pages
Stockholm: Department of Analytical Chemistry, Stockholm University, 2010. 77 p.
Keyword
Mass spectrometry, ESI-MS, SALDI-MS, Electrocapture, Sample treatment
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-32236 (URN)978-91-7155-981-4 (ISBN)
Public defence
2010-01-22, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: In PressAvailable from: 2009-12-17 Created: 2009-12-07 Last updated: 2011-08-31Bibliographically approved
2. Novel Solid Phase Extraction and Mass Spectrometry Approaches to Multicomponent Analyses in Complex Matrices
Open this publication in new window or tab >>Novel Solid Phase Extraction and Mass Spectrometry Approaches to Multicomponent Analyses in Complex Matrices
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Analysis of compounds present in complex matrices is always a challenge, which can be partly overcome by applying various sample preparation techniques prior to detection. Ideally, the extraction techniques should be as selective as possible, to minimize the concentration of interfering substances. In addition, results can be improved by efficient chromatographic separation of the sample components. The elimination of interfering substances is especially important when utilizing mass spectrometry (MS) as a detection technique since they influence the ionization yields. It is also important to optimize ionization methods in order to minimize detection limits.

In the work this thesis is based upon, selective solid phase extraction (SPE) materials, a restricted access material (RAM) and graphitized carbon black (GCB) were employed for clean up and/or pre-concentration of analytes in plasma, urine and agricultural drainage water prior to liquid chromatography/mass spectrometry (LC/MS). Two SPE formats, in which GCB was incorporated in µ-traps and disks, were developed for cleaning up small and large volume samples, respectively. In addition, techniques based on use of sub-2 µm C18 particles at elevated temperatures and a linear ion trap (LIT) mass spectrometer were developed to improve the efficiency of LC separation and sensitivity of detection of 6-formylindolo[3,2-b]carbazole (FICZ) metabolites in human urine.

It was also found that GCB can serve not only as a SPE sorbent, but also as a valuable surface for surface-assisted laser desorption ionization (SALDI) of small molecules. The dual functionality of GCB was utilized in a combined screening-identification/quantification procedure for fast elimination of negative samples. This may be particularly useful when processing large numbers of samples. SALDI analyses of small molecules was further investigated and improved by employing two kinds of new surfaces: oxidized GCB nanoparticles and silicon nitride.

Place, publisher, year, edition, pages
Stockholm: Department of Analytical Chemistry, Stockholm University, 2010. 62 p.
Keyword
Sample preparation, SPE, RAM, GCB µ-trap, GCB disk, High temperature LC, LC/MS, ESI, APCI, Matrix effects, LIT-MS, SALDI, Sample screening, Oxidized GCB, Silicon nitride
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-38625 (URN)978-91-7447-050-5 (ISBN)
Public defence
2010-06-02, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2010-05-11 Created: 2010-04-22 Last updated: 2010-05-04Bibliographically approved

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