Virtual instruments for flow-based and discrete analytical methods

Kuljanin, Aleksandra (author), Gros, Nataša (mentor), Lotrič, Uroš (comentor)

In the field of analytical chemistry, the use of virtual instruments is still mostly limited to signal acquisition and instrument control. The developed platforms are focused on a specific analytical method or determination. By utilizing the multichannel capabilities of the LabVIEW environment, platforms of wider functionality can be created, and there are many possibilities for further development and improvements. The starting point was an already developed, virtually-supported LabVIEW platform for flow-based and discrete analytical methods. The work within this thesis was focused on additional extension and upgrading of the platform. Through software modifications, hardware components for multipoint conductometric detection were integrated into the virtually-supported sequential injection analysis system. Furthermore, a new virtual instrument was developed to process peak signals and calculate key zone penetration parameters. The spectrometric microchamber, part of the virtually-supported microtitrator, was redesigned for conductometric monitoring. The number of physical and chemical factors affecting the SIA-gram peak profile is large, and the behavior of the plug within the liquid conduits cannot be accurately predicted. Developed virtual instrument for peak processing and calculation of most important zone penetration parameters in combination with multipoint conductivity monitoring enabled prompt and accurate insight into the behavior of the plugs of different chemical composition. The influences of flow rate, plug volume and coil length on peak profiles and peak overlapping, for plugs of different chemical composition, were studied by using multivariate analysis. Under studied set of conditions, it was shown that the total overlapping area parameter highly correlate with experimental peak absorbance maxima values (R2 > 0.99) for the reactions that employ the same plug medium. This was confirmed on the example of two reactions with different kinetics, the reaction of iron(II) with ferrozine and the reaction of copper(II) with EDTA. By applying the established correlation, absorbance peak maxima can be calculated for the conditions which were not tested experimentally, which significantly reduces the total number of experiments and chemical consumption in later optimization phases. It was also shown that detailed studies of the total overlapping area and the overlapping fraction of the reagent peak can be useful for defining the parameters’ range for high reagent utilization and adequate method sensitivity. The operating capabilities of the redesigned microchamber were confirmed for monitoring urea decomposition catalysed by Jack bean urease. In this way, the platform gained additional functionality as another detection method was integrated into the virtually-supported microtitrator. The virtually-supported multipoint conductometric detection is a starting point for the introduction of other electroanalytical methods and further extension of the platform. The spectrometric microchamber can be remodeled into a dual-detection microchamber, to simultaneously monitor changes in absorbance and conductivity.

• Language: English
• Keywords: LabVIEW, virtual instruments, multifunctional analytical platforms, multipoint detection, conductivity, sequential injection analysis
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2023
• PID: 20.500.12556/RUL-145324
• COBISS.SI-ID: 149992707
• Publication date in RUL: 17.04.2023

Secondary language

• Language: Slovenian
• Title: Virtualni instrumenti za pretočne in diskretne analizne metode

Abstract

V analizni kemiji se uporabljajo virtualni instrumenti predvsem za zajem signala in nadzor instrumentov. Obstoječa virtualna okolja se osredotočajo na specifično analizno metodo ali določitev. Z dodatnim izkoriščanjem večkanalnih zmogljivosti okolja LabVIEW smo ustvarili večfunkcionalno virtualno okolje, ki širi možnosti uporabe. Osnova za to nalogo je bilo že razvito, LabVIEW virtualno podprta platforma za pretočne in diskretne analizne metode. Z reprogramiranjem smo v virtualno okolje vključili komponente strojne opreme za večtočkovno konduktometrično detekcijo v virtualno podrti sekvenčni injekcijski sistem. Poleg tega smo razvili tudi virtualni instrument za obdelavo signalov vrhov in izračun ključnih parametrov prodiranja con. Spektrometrično mikrokomoro, ki je del virtualno podprtega mikrotitratorja, smo nadgradili za konduktometrično spremljanje. Na profil vrha SIA-grama vpliva veliko število fizikalnih in kemičnih dejavnikov, zato je zelo težko predvideti tokovni profil con. Razviti virtualni instrument za obdelavo vrhov in izračun najpomembnejših parametrov penetracije con omogoča, da v kombinaciji z večtočkovnim nadzorom prevodnosti dobimo hiter in natančen vpogled v obnašanje con različne sestave. Z uporabo multivariatne analize smo preučili, kako na tokovni profil con različne sestave vplivajo pretok, prostornina reagenta in dolžina mešalne tuljave. Pod preučevanim nizem pogojev smo dokazali, da parameter skupne površine prekrivanja močno kolerira z maksimalnimi vrednostmi eksperimentalno določene absorbance (R2 > 0.99) za reakcije, pri katerih smo uporabili isti medij. To smo potrdili z dvema reakcijama z različno kinetiko, za reakcijo železa(II) s ferozinom in za reakcijo bakra(II) z EDTA. Z uporabo opisane korelacije je možno predvideti maksimume vrhov absorbance, kar bistveno zmanjša število poskusov in porabo reagentov pri optimizaciji metode. Pokazalo se je tudi, da lahko študijo celotnega prekrivajočega se območja in študijo deleža prekrivajočega se vrha reagenta uporabimo za definiranje razpona parametrov visoke izkoriščenosti reagenta in za definiranje ustrezne občutljivosti metode. Preoblikovano mikrokomoro smo uporabili za spremljanje razgradnje sečnine, ki jo katalizira ureaza fižola. Na ta način smo pridobili dodatno funkcionalnost, saj smo v virtualno podprt mikrotitrator dodali drugo metodo zaznavanja. Virtualno podprta večtočkovna konduktometrična detekcija je izhodišče za uvajanje drugih elektroanaliznih metod in nadaljnjo širitev platforme. Spektrometrično mikrocelico je mogoče pretvoriti v mikrocelico z dvojnim zaznavanjem za istočasno spremljanje absorbance in prevodnosti.

• Keywords: LabVIEW, virtualni instrumenti, večnamenske analizne platforme, večtočkovna detekcija, prevodnost, sekvenčna injekcijska analiza