Ionization efficiency in electrospray ionization source and its relations to compounds’ physico-chemical properties
Failid
Kuupäev
2021-07-12
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Abstrakt
Vedelikkromatograafi-massispektromeetria (LC-MS) võimaldab tuvastada erinevates proovides väga erinevaid ühendeid ja on tõusnud praegusel ajal domineerivaks analüüsimeetodiks orgaaniliste ühendite madalate sisalduste määramisel. Selle süsteemi üks võtmekomponente on ioonallikas, mida kasutatakse LC-MS aparatuuri juures nende kahe liidesena. Elektropihustusionisatsiooni (ESI) ioonallikas on tänu sellele, et võimaldab ioniseerida ja analüüsida väga laia omaduste spektri ja massivahemikuga ühendeid üks enimkasutatavaid ioonallikaid massispektromeetrias. Vaatamata ESI populaarsusele, ei ole siiani päris selge, millised ühendite füsiko-keemilised omadused määravad aine ioniseerumise effektiivsuse ESI allikas. Nimelt, erinevad ühendid võivad anda sama kontsentratsiooni juures massispektris väga erineva intensiivsusega signaale.
Käesoleva töö peamiseks eesmärgiks oli jõuda seosteni, mis määravad ühendi ionisatsiooni efektiivsuse ESI allikas lähtudes ühendi füsiko-keemilistest parameetritest. Selleks töötati välja metoodika analüüsimaks erinevaid ühendeid samadel tingimustel ESI massispektromeetriga. Selle tulemusena on loodud suhteliste ionisatsioonieffektiivsuste skaala (solvendisüsteemis 80% - atsetonitriili, 20% - 0.1% sipelghappe vesilahust), mis hetkel sisaldab 344 väga erinevate füsiko-keemiste omadustega ühendit. Kaasates kõiki analüüsitud ühendeid ja nende 11 parameetrit (aluselisus vees, atsetonitriilis ja gaasifaasis, osakese pindala, ruumala, molekulmass, dipoolmoment, polaarse pinna suurus, lipofiilsus/hüdrofoobsus, protoneerumistsenter ja laengu jaotumist iseloomustav parameeter) viidi läbi multilineaarne regressioonanalüüs (MLR) leidmaks peamised seosed mainitud parameetrite ning ühendi ionisatsioonieffektiivsuse vahel ESI allikas kasutatud tingimustel. Kuna kõigi analüüsitud ühendite jaoks ei ole eksperimentaalseid parameetrite väärtuseid, siis käesoleva töö raames arvutati puuduvad väärtused kõigile ühenditele ja kasutati neid MLR analüüsis.
MLR analüüsi tulemusena joonistuvad selgelt välja seosed ühendi ionisatsioonieffektiivsuse (ESI allikas antud tingimustel) ning kolme füsiko-keemilise omaduse vahel: aluselisus (vesilahuses), molekuli/iooni suurus ja iooni lipofiilsus/hüdrofoobsus. Mida tugevamini väljendunud on ainel need kolm omadust, seda intensiivsemalt see ESI allikas ioone annab.
Käesolev töö on suure olulisusega kõigile, kes töötavad LC-ESI-MS meetodiga.
Liquid chromatography mass spectrometry (LC-MS) enables to identify various compounds from different samples and it is currently the dominant method for detecting organic compounds in low concentrations. Ion source is the interface between the LC and MS and is a key component of an LC-MS apparatus. One of the most widely applied ionization source in mass spectrometry is electrospray ionization source (ESI) due to its capability to ionize and analyse different compounds with wide span of parameters’ values. Despite of the commonness of ESI-MS the relationships between the ionization efficiency and compounds’ physico-chemical parameters have still not been fully elucidated. The signals in mass-spectrum of different compounds having the same concentration in the sample can vary strongly. The main purpose of this study was to analyse the relationships between ionisation efficiencies and physico-chemical properties of analytes and find out which physico-chemical parameters influence ionization efficiency the most. The ESI-MS method for analysing the ionization efficiencies of various compounds under the same experimental conditions and the scale of relative ionization efficiencies of 344 compounds with widely differing physico-chemical parameter values (in solvent system 80% - acetonitrile, 20% - 0.1%formic acid aqueous solution) was developed. Multilinear regression analysis involving all the analysed compounds and the 11 physico chemical parameters (basicity in acetonitrile, in water and gas phase basicity, the area and the volume of the particle, molecular mass, dipole moment, polar surface area, lipophilicity/hydrophobicity, protonation centre and the (de)localization of the charge on the surface of the particle) was used to determine the most relevant relations between ionization efficiencies and those parameters. Since the experimental data on some of those parameters is not available, the computational values were calculated for all the compounds and used in multilinear regression analysis when experimental values were not available. The results of MLR analysis enable concluding that three main descriptors of compound determine its ionization efficiency in ESI source under the used conditions: the basicity on aqueous solution, the size of the ion/molecule and the lipophilicity/hydrophobicity of the ion. The more strongly these mentioned parameters of compounds are expressed, the more intensive is ionization in ESI source. This study is expected to be significant to all chemists and researchers working with the LC-ESI-MS method.
Liquid chromatography mass spectrometry (LC-MS) enables to identify various compounds from different samples and it is currently the dominant method for detecting organic compounds in low concentrations. Ion source is the interface between the LC and MS and is a key component of an LC-MS apparatus. One of the most widely applied ionization source in mass spectrometry is electrospray ionization source (ESI) due to its capability to ionize and analyse different compounds with wide span of parameters’ values. Despite of the commonness of ESI-MS the relationships between the ionization efficiency and compounds’ physico-chemical parameters have still not been fully elucidated. The signals in mass-spectrum of different compounds having the same concentration in the sample can vary strongly. The main purpose of this study was to analyse the relationships between ionisation efficiencies and physico-chemical properties of analytes and find out which physico-chemical parameters influence ionization efficiency the most. The ESI-MS method for analysing the ionization efficiencies of various compounds under the same experimental conditions and the scale of relative ionization efficiencies of 344 compounds with widely differing physico-chemical parameter values (in solvent system 80% - acetonitrile, 20% - 0.1%formic acid aqueous solution) was developed. Multilinear regression analysis involving all the analysed compounds and the 11 physico chemical parameters (basicity in acetonitrile, in water and gas phase basicity, the area and the volume of the particle, molecular mass, dipole moment, polar surface area, lipophilicity/hydrophobicity, protonation centre and the (de)localization of the charge on the surface of the particle) was used to determine the most relevant relations between ionization efficiencies and those parameters. Since the experimental data on some of those parameters is not available, the computational values were calculated for all the compounds and used in multilinear regression analysis when experimental values were not available. The results of MLR analysis enable concluding that three main descriptors of compound determine its ionization efficiency in ESI source under the used conditions: the basicity on aqueous solution, the size of the ion/molecule and the lipophilicity/hydrophobicity of the ion. The more strongly these mentioned parameters of compounds are expressed, the more intensive is ionization in ESI source. This study is expected to be significant to all chemists and researchers working with the LC-ESI-MS method.
Kirjeldus
Väitekirja elektrooniline versioon ei sisalda publikatsioone
Märksõnad
electrospray ionization, physical properties, chemical properties