Quantitative relative equilibrium constant measurements in supramolecular chemistry
Date
2017-06-29
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Abstract
Keemiline analüüs mängib olulist rolli nii meditsiinis, keemia tööstuses kui keskkonna kaitses. Patsiendi tervise või mürgiste kemikaalide sisalduse jälgimine keskkonnas vajab täpseid analüüsi meetodeid. Tundlikud ja selektiivsed meetodid põhinevad tavaliselt keerukal aparatuuril, mis on küllaltki kallis ja vajab väljakoolitatud eksperte. Üldjuhul on vajalik ka prooviettevalmistus, kus huvipakkuv keemiline ühend eraldatakse, kontsentreeritakse või muundatakse keemiliselt, et muuta proov instrumenti sisestamiseks sobilikuks. Tehislikud (sünteetilised) retseptorid imiteerivad bioloogilistes süsteeme. Sellised ühendid võiksid leida kasutust keemilise sensori ehituses, mida saaks potentsiaalselt rakendada ilma proovi eeltöötlemise või labori varustuseta. Sobilike retseptorite väljatöötamisel on oluline nende sobilikkuse uurimine. Käesoleva uurimustöö raames keskenduti täpsete seondumistugevuse mõõtmisemeetodite arendamisele. Seondumiskonstantide mõõtmisel on oluliseks mõjuriks uuritava analüüdi sisalduse täpne teadmine. Suhtelised keemilise tasakaalu määramise meetodid omavad selles vallas eelist. Nimelt ei ole vajalik meil teada analüüdi täpset kogust mõõtmise käigus. Meetodite rakendatavust katsetati kahel instrumentaaltehnikal: UV-vis spektrofotomeetrial ja tuumamagnetresonants spektromeetrial (TMR). TMR baasil versioon võimaldab mõõta mitu seondumiskonstanti ühe mõõtmisega. Puuduseks on selle madalam tundlikkus, mille tõttu on vajalik suurem kogus ainet. TMR põhise suhtelise seondumisafiinsusmõõtmise meetodi usaldusväärsust uuriti UV-vis spektrofotomeetriaga. Mõlemate mõõtemeetodite tulemused näitavad head kooskõla. Lisaks mõõtmismeetodite arendusele keskenduti ka karboksülaat anioonide (negatiivselt laetud ühendid) seondumise uurimisele ja karakteriseerimisele. Üheks uuritud ühendiks oli üks kasutatavamaid taimekaitsevahendeid maailmas, glüfosaat. Väikesed muutused retseptori ehituses toovad esile suuri muutusi glüfosaadi seondumises. Esitatud tulemused on olulised edasiste supramolekulaarsete ühendite väljatöötamisel, hinnates nende happelis-aluselisi, vesiniksideme donoorseid ja seondumise omadusi
Chemical analysis plays key role in medicine, chemical production or environmental protection. Monitoring patient health or presence of toxic compounds in the environment requires precise analytical methods. Sensitive and selective methods commonly use intricate instruments like chromatographs coupled with mass-spectrometric systems to determine desired chemical compounds at very low concentrations. Instrumental systems are expensive and require trained personnel to use it. Also, usually samples need pre-treatment before analysis. Synthetic receptors mimic natural receptors in biological systems e.g., sensing smell and feeling taste. Such compounds could find practical application as sensing elements in chemical sensors. A sensor could be used potentially without sample preparation and laboratory equipment. Receptor’s suitability can be estimated by studying its physical-chemical properties and behaviour towards potential analytes. This PhD study focuses on development of accurate binding constant methods. Binding constants can be used to characterize binding sensitivity and selectivity. Measurement accuracy is strongly affected during these measurements. By measuring relative equilibrium constants this can be disregarded. Method applicability was tested on two instrumental techniques: UV-vis spectrophotometry and nuclear magnetic resonance spectrometry (NMR). NRM based version enables to measure several binding constants in a single measurement. Drawback is its need for more compound for measurements. Comparison of two techniques showed good agreement with each other. Aside from developing binding constant measurement methods, there was a strong focus on studying the binding behaviour of carboxylate anions. One of which was glyphosate, a widely used herbicide. Small changes in receptor structure cause big changes in binding properties. Results discussed in this dissertation serve as an important stepping stone for developing new receptors and testing their suitability for sensor building applications.
Chemical analysis plays key role in medicine, chemical production or environmental protection. Monitoring patient health or presence of toxic compounds in the environment requires precise analytical methods. Sensitive and selective methods commonly use intricate instruments like chromatographs coupled with mass-spectrometric systems to determine desired chemical compounds at very low concentrations. Instrumental systems are expensive and require trained personnel to use it. Also, usually samples need pre-treatment before analysis. Synthetic receptors mimic natural receptors in biological systems e.g., sensing smell and feeling taste. Such compounds could find practical application as sensing elements in chemical sensors. A sensor could be used potentially without sample preparation and laboratory equipment. Receptor’s suitability can be estimated by studying its physical-chemical properties and behaviour towards potential analytes. This PhD study focuses on development of accurate binding constant methods. Binding constants can be used to characterize binding sensitivity and selectivity. Measurement accuracy is strongly affected during these measurements. By measuring relative equilibrium constants this can be disregarded. Method applicability was tested on two instrumental techniques: UV-vis spectrophotometry and nuclear magnetic resonance spectrometry (NMR). NRM based version enables to measure several binding constants in a single measurement. Drawback is its need for more compound for measurements. Comparison of two techniques showed good agreement with each other. Aside from developing binding constant measurement methods, there was a strong focus on studying the binding behaviour of carboxylate anions. One of which was glyphosate, a widely used herbicide. Small changes in receptor structure cause big changes in binding properties. Results discussed in this dissertation serve as an important stepping stone for developing new receptors and testing their suitability for sensor building applications.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone
Keywords
supramolekulaarühendid, keemiline tasakaal, spektrofotomeetria, supramolecular compounds, chemical equilibria, spectrophotometry