MASARYK UNIVERSITY


                                        Faculty of Science

                                      Department of Chemistry






                      Separation Methods and  Mass Spectrometry Applications



                                           Ph.D. THESIS



                                        ANNAPURNA PAMREDDY


                             Supervisor: Prof. RNDr. Josef Havel, DrSc


                                          Brno, May 2014






Introduction


Mass spectrometry is now used across a broad range of disciplines and settings, including academic
research, biotechnological development, pharmaceutical discovery, clinical testing, environmental
analysis and geological testing. Several analytical methods have been developed for the
determination of antibiotics in various environmental matrices (e.g. wastewater, soil, sludge, and
manure) can be found in the literature. The analytical procedures consisted of the extraction of
the compounds from sludge, clean-up of the extracts and analysis by chromatographic techniques
(liquid or gas chromatography coupled with mass spectrometry). The extraction of antibiotics from
sludge is affected by the various adsorption mechanisms, such as hydrogen bonding, cation exchange,
hydrophobic interactions and complexation involved in their retention in the solid phase. For the
determination of antibiotics, liquid chromatography (LC) with both diode-array (DAD) and mass
spectrometry detection (MS) or tandem MS have been used. LC-MS/MS is the most widely employed in
the determination of antibiotics in complex matrices due to its high sensitivity, selectivity and
its ability to provide compound information.

    Nanoparticles form aggregates which refer the accumulation of several nanoparticles. The
aggregation of nanoclusters is well known and several papers have been reported on this issue. Mass
spectrometry is considered as one of the significant analytical tools in analytical chemistry as it
is employed to analyze organic, inorganic and biological molecules such as proteins,
oligonucleotides, carbohydrates, and lipids.

   In this work, the formation of various nanoclusters via Laser Desorption and Ionization (LDI),
Matrix Assisted Laser Desorption and Ionization (MALDI) and/or Laser Ablation (LA) was studied
using Time Of Flight Mass Spectrometry (TOF MS) and Quadrupole Ion Trap Time-Of-Flight Mass
Spectrometry (QIT-TOF-MS). Also the aim was to contribute towards the understanding of processes
which could take place in the plasma plume formed during the ionization. The knowledge about the
clusters formation is essential for nano-technology and it might also be useful to study
nanoparticles interactions with biomolecules.




Abstract (in English)


Mass spectrometry is a sensitive technique used to detect, identify and quantitate molecules based
on their mass and charge (m/z).The Thesis deals with the applications of Laser Desorption and
Ionization (LDI) and/or Matrix-Assisted Laser Desorption and Ionization (MALDI) Time of Flight Mass
Spectrometry (TOF MS)/Quadrupole Ion Trap Time-Of-Flight Mass Spectrometry (QIT-TOF-MS) analysis of
various nano-materials or nano-layers and with laser ablation synthesis of arsenic phosphides,
piperazine and it’s derivatives.

Several different chemical materials including nano-materials like gold nano particles (GNPs),
nano-diamonds, pre cursors of arsenic phosphides, Si wafers,  piperazine and it’s derivatives, etc.
were analyzed using either LDI or MALDI TOF MS or QIT-TOF-MS. The stoichiometry of the clusters was
determined via isotopic envelope analysis and computer modelling. Primarily, in all studies the
optimal laser power conditions for the cluster generation under applied experimental set up were
always searched for and the formation of various clusters in the plasma plume during the LDI and/or
MALDI ionization of used nano materials was examined also with respect to understand processes
during the pulsed laser deposition of nano-materials (like Si wafers). The results contribute to
the understanding of chemical bonding in studied materials. Original results concerning the laser
ablation synthesis of arsenic phosphides from nano – precursors were obtained.


Abstrakt (in Czech)


Hmotnostní spektrometrie je citlivá metoda, užívaná k detekci, identifikaci a kvantifikaci molekul
využitím rozdílů v poměru hmotnosti a náboje (m/z). Předkládaná disertační práce se zabývá
aplikacemi ionizace laserovou desorpcí (Laser Desorption and Ionization, LDI), resp. ionizace
laserovou desorpcí s použitím matrice (Matrix-Assisted Laser Desorption and Ionization, MALDI) ve
spojení s Time of Flight (TOF) hmotnostní spektrometrií (TOF-MS) nebo TOF hmotnostní spektrometrií
s kvadrupólovou iontovou pastí (QIT-TOF-MS) k analýze různých druhů nanomateriálů a nanovrstev a
laserovou ablační syntézou fosfidů arsenu a derivátů piperazinu.

Studované materiály, jako jsou např. nanomateriály (nanočástice zlata, nanodiamanty), prekurzory
pro přípravu fosfidů arsenu, Si wafery, piperazin a jeho deriváty, aj., byly analyzovány buď LDI
nebo MALDI s TOF-MS nebo QIT-TOF-MS. Stechiometrie získaných klastrů byla určena metodou analýzy
izotopových “obalových křivek” (isotopic envelope analysis) a pomocí počítačového modelování. Pro
všechny studované materiály byla určena energie laseru, optimální pro tvorbu klastrů za daných
experimentálních podmínek. Tvorba klastrů v plazmovém výboji během LDI a/nebo MALDI ionizace
analyzovaných materiálů byla studována také ohledem na objasnění procesů k nimž dochází během
depozice nanomateriálů pomocí pulsního laseru (např. na Si wafery). Získané výsledky umožňují
porozumět chemickým vazbám ve studovaných materiálech. Originální výsledky byly získány studiem
laserové ablační syntézy fosfidů arsenu z příslušných prekurzorů.












Date: 08.01.2014                                                        ANNAPURNA PAMREDDY