Comparison and optimisation of novel mass spectrometry ionisation sources
Date
2016-07-05
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Abstract
Vedelikkromatograafia-massispektromeetria (LC/MS) on laialt kasutatav meetod väga mitmekesiste analüüside teostamiseks nii rutiin- kui teaduslaborites. LC/MS meetodiga määratakse näiteks taimekaitsevahendeid toiduainetes, erinevaid plastiku komponente sellega kokkupuutuvates produktides, narkootikume veres, seedimise käigus organismis tekkivaid ühendeid, rakkudes leiduvaid valke jne, tegemist on ühe oluliseima meetodiga analüüsimaks komponente segudest. Ionisatsiooniallikas on kahe meetodi (vedelikkromatograafia ja massispektromeetria) ühendamiseks oluline liides, mille abil tekitatakse kromatograafist tulevast vedelikust analüüdimolekulide ioonid, mida analüüsitakse massispektromeetriga. Erinevaid ionisatsiooniallikaid on mitmeid ning pidevalt täiendatakse olemasolevaid ja leiutatakse uusi. Seetõttu on vajalik võrrelda erinevaid uusi ionisatsiooniallikaid, et leida millised on spetsiifilise töö jaoks parimad.
Antud töö käigus võrreldi mitmeid uusi ionisatsiooniallikaid kommertsiaalselt levinud elektropihustus ionisatsiooni allikaga (ESI) ning näidati ESI eeliseid võrreldes uudsemate allikatega, mis on popullaarseks muutumas, kuid pole läbinud võrdluse kadalippu, et õigustada nende kasutamist.
Samuti oli töö eesmärgiks meie töögrupis eelnevalt väljatöötatud uudse ESI allika pihusti (3R) optimeerimine, mis viidi edukalt lõpule. Optimeerimise tulemused näitavad, uudse 3R pihusti eelised seisnevad peamiselt madalamates avastamispiirides ja robustsuses võrreldes kommertsiaalse allikaga.
Samuti täideti edukalt uudse pihustiga seotud teine eesmärk: võrreldi kommertsiaalse pihustiga praktilise analüüsi näitel. 3R pihusti eelised võrreldes kommertsiaalse pihustiga seisnesid väiksemate ainekoguse usaldusväärsemas määramises ning paremas korduvuses.
Antud töös leitud erinevate ionisatsiooniallikate võrdlusandmed ning uudse ESI pihusti iseloomustamisel leitud eelised lisavad olulist informatsiooni väga mitmekesisele MS ionisatsiooniallikate temaatikale. Teadlased püüdlevad ühest küljest aina universaalsemate allikate poole, kuid samas otsitakse allikaid väga spetsiifiliste analüüside teostamiseks, mis annaksid parimaid tulemusi. Selleks on vajalik aina uuesti võrrelda praeguseid parimaid allikaid uudsete leiutistega, et leida effektiivseim liides LC/MS meetodile.
LC/MS method is widely used in routine analysis and research laboratories. LC/MS method is used for example pesticide analysis in food stuffs, plastic components from the products stored in plastics, toxicological studies in blood, components of human cells and the products of the processes happening inside tissues etc. This is a very small part of the wide range of analysis that rely on LC/MS method. There are numerous novel developments aiming to improve the interface between LC and MS. Novel commercial ion sources need to be compared with each other in order to evaluate their advantages. For some novel ion sources the comparison has been done in this study, occasionally with surprising results. Comparison of the conventional ESI source with some of the newer developments in commercial ionisation sources, such as heated electrospray (HESI), multimode (MMI) source and APPI sources demonstrated that the ESI source is on an average the most robust and sensitive method for generating ions in the interface of LC and MS. The novel 3R nebuliser for ESI source recently developed in our group was compared to the conventional ESI source. Analysis of the main nebuliser parameters affecting the ionisation showed that the inner gas capillary pressure and internal diameter as well as the liquid capillary internal diameter had the strongest influence on the results. The importance of the outer gas capillary pressure, responsible of the nebulisation in the conventional ESI nebuliser, proved to be much less important than the gas pressure in the inner gas capillary, showing the advantage of the novel approach to ESI nebuliser. In a practical comparison – neonicotinoids in honey samples–with the native commercial nebuliser the 3R nebuliser proved to be comparable or better. The aims of the thesis were fulfilled successfully, but many more novel ion source developments need to be evaluated and the work on improving the LC/MS method as such is far from done. This study is expected to add valuable information for the improvement of the LC/MS method and proposes a new direction for the improvement of ESI source.
LC/MS method is widely used in routine analysis and research laboratories. LC/MS method is used for example pesticide analysis in food stuffs, plastic components from the products stored in plastics, toxicological studies in blood, components of human cells and the products of the processes happening inside tissues etc. This is a very small part of the wide range of analysis that rely on LC/MS method. There are numerous novel developments aiming to improve the interface between LC and MS. Novel commercial ion sources need to be compared with each other in order to evaluate their advantages. For some novel ion sources the comparison has been done in this study, occasionally with surprising results. Comparison of the conventional ESI source with some of the newer developments in commercial ionisation sources, such as heated electrospray (HESI), multimode (MMI) source and APPI sources demonstrated that the ESI source is on an average the most robust and sensitive method for generating ions in the interface of LC and MS. The novel 3R nebuliser for ESI source recently developed in our group was compared to the conventional ESI source. Analysis of the main nebuliser parameters affecting the ionisation showed that the inner gas capillary pressure and internal diameter as well as the liquid capillary internal diameter had the strongest influence on the results. The importance of the outer gas capillary pressure, responsible of the nebulisation in the conventional ESI nebuliser, proved to be much less important than the gas pressure in the inner gas capillary, showing the advantage of the novel approach to ESI nebuliser. In a practical comparison – neonicotinoids in honey samples–with the native commercial nebuliser the 3R nebuliser proved to be comparable or better. The aims of the thesis were fulfilled successfully, but many more novel ion source developments need to be evaluated and the work on improving the LC/MS method as such is far from done. This study is expected to add valuable information for the improvement of the LC/MS method and proposes a new direction for the improvement of ESI source.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone.
Keywords
vedelikukromatograafia, massispektromeetria, ionisatsioon, optimeerimine, liquid cromatography, mass spectrometry, ionization, optimization