Development of a colorimetric sensor receptor for the detection of biogenic amines

Diplomsko delo predstavlja razvoj kolorimetričnega senzorskega receptorja (KSR) za zaznavanje trimetilamina, ki skupaj z dimetilaminom in amonijakom tvori enega glavnih parametrov kakovosti hrane ‒ celokupni hlapni bazični dušik ali TVB-N (angl. total volatile basic nitrogen). KSR, ki smo ga razvili, je sestavljen iz izključno z živili združljivih materialov: indikatorja (izvleček vijoličnega korenja) in polimerne osnove (derivat celuloze), ki smo ju v obliki polimerne raztopine nanesli na nosilec iz PET-folije . Za spremljanje barvnih sprememb tako pripravljenega KSR smo pripravili zaprt sistem, ki posnema pogoje v živilski embalaži ter vanj s tehniko vzorčenja iz nezapolnjenega prostora nad vzorcem injicirali analit. Kolorimetrično detekcijo in RGB-analizo smo izvedli s pametnim telefonom in brezplačno dostopno aplikacijo Color Grab. Potrdili smo, da so optične lastnosti indikatorja odvisne od koncentracije trimetilamina in v izbranem koncentracijskem območju dobili barvno lestvico od rdeče-vijolične do temno sive barve. Ugotovitve diplomske naloge so dobro izhodišče za nadaljnje raziskave in izpopolnjevanje tako KSR kot tudi metode. Ker kolorimetrična detekcija s pametnim telefonom ne zahteva usposobljenega osebja in je veliko cenejša ter hitrejša od uveljavljenih instrumentalnih metod, ki se sicer uporabljajo za določanje biogenih aminov, ima ta metoda velik potencial na področju spremljanja kakovosti in varnosti hrane. Morebitna uporaba kolorimetričnih senzorskih receptorjev v sklopu pametnega pakiranja živil bi lahko znatno zmanjšala količino zavržene hrane.The bachelor thesis presents the development of a colorimetric sensor receptor (CSR) for the detection of trimethylamine. Along with dimethylamine and ammonia, this analyte forms one of the main food quality parameters – total volatile basic nitrogen (TVB-N). The developed CSR consists of entirely food-compatible materials: an indicator (black carrot extract) and a polymer matrix (cellulose derivative), from which a polymer solution was prepared to later coat a solid-state substrate (a PET-foil). For the purpose of monitoring the color changes of CSR, a closed system that mimics conditions in food packaging was created and analyte injected according to the headspace method. Colorimetric detection and RGB analysis were performed using a smartphone and a commercially available application Color Grab. We confirmed that optical properties of the indicator depend on the concentration of trimethylamine and observed visible color changes from red-purple to dark gray. The presented findings are a good starting point for further improvement of the CSR and the method. Smartphone-based colorimetric detection does not require trained personnel and is much cheaper and faster than conventional instrumental techniques for the determination of biogenic amines. Therefore, sensing systems compatible with smartphone-based colorimetric detection offer a promising solution for monitoring of food quality and food safety. CSR integrated into smart food packaging have the potential to significantly reduce the amount of food waste

Application of UHPLC-HRMS for determination of organic compounds in samples of psychoactive substances and food supplements

Magistrsko delo predstavlja uporabo tekočinske kromatografije ultra visoke ločljivosti, sklopljene z masno spektrometrijo visoke ločljivosti (angl. ultra high performance liquid chromatography – high resolution mass spectrometry, UHPLC-HRMS) za analizo psihoaktivnih snovi in prehranskih dopolnil. Razvili smo metodo za identifikacijo večjega števila organskih snovi. Za določanje organskih snovi v vzorcih je bila uporabljena kombinacija na novo razvite metode UHPLC-HRMS z metodami infrardeče spektroskopije s Fourierovo transformacijo na oslabljen totalni odboj (angl. attenuated total reflectance Fourier-transform infrared spectroscopy, ATR-FTIR), tekočinske kromatografije visoke ločljivosti z detektorjem z nizom diod (angl. high performance liquid chromatography with diode aray detector, HPLC-DAD) in plinske kromatografije, sklopljene z masno spektrometrijo (angl. gas chromatography – mass spectrometry, GC-MS), ki jih uporabljajo v Nacionalnem laboratoriju za zdravje, okolje in hrano (NLZOH). Analizirani so bili trije vzorci psihoaktivnih snovi na osnovi heksahidrokanabinola (angl. hexahydrocannabinol, HHC) in 58 vzorcev prehranskih dopolnil. V vzorcih psihoaktivnih snovi smo identificirali štiri različne nove psihoaktivne snovi (NPS), in sicer HHC, heksahidrokanabinol acetat (angl. hexahydrocannabinol acetate, HHC-O), heksahidrokanabiforol (angl. hexahydrocannabiphorol, HHC-P) in hidroksiheksahidrokanabinol (angl hydroxyhexahydrocannabinol, OH-HHC), ter 37 različnih organskih spojin v vzorcih prehranskih dopolnil. Na Evropski center za spremljanje drog in zasvojenosti z drogami (angl. European Monitoring Centre for Drugs and Drug Addiction, EMCDDA) smo poročali prvo identifikacijo HHC-O v Sloveniji. Pri analizi vzorcev prehranskih dopolnil so bile ugotovljene nepravilnosti pri 15 % analiziranih vzorcev. Problematični so bili predvsem izdelki, kupljeni na spletu, ki so vsebovali zaviralce fosfodiesteraze tipa 5 (angl. phosphodiesterase type 5, PDE5) in njihove derivate ter anorektike, kot je sibutramin. Razvita metoda predstavlja dobro orodje za analize tako psihoaktivnih snovi, katerih proizvodnja se zelo hitro razvija, kot tudi prehranskih dopolnil, ki so na spletu prosto dostopne vsakomur, vendar lahko vsebujejo zdravju škodljive ali celo življenjsko nevarne snovi. Metoda omogoča identifikacijo velikega števila organskih spojin, z uporabo raztopin standardov pa bi z njo lahko v prihodnosti določali tudi vsebnost teh potencialno nevarnih spojin v vzorcih in tako preprečili morebitne zdravstvene zaplete pri njihovi uporabi.The master\u27s thesis presents the use of ultra high performance liquid chromatography – high resolution mass spectrometry (UHPLC-HRMS) for the analysis of psychoactive substances and food supplements. A method for identification of a wide range of organic substances was developed. A combination of the newly developed UHPLC-HRMS method and National laboratory of health, environment and food\u27s (NLZOH) attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), high performance liquid chromatography with diode aray detector (HPLC-DAD), and gas chromatography – mass spectrometry (GC-MS) methods was used to determine organic substances in the samples. A total of 3 hexahydrocannabinol (HHC) based psychoactive substance samples and 58 food supplement samples were analysed. We identified 4 different new psychoactive substances (NPS) in the samples of psychoactive substances (HHC, hexahydrocannabinol acetate (HHC-O), hexahydrocannabiphorol (HHC-P), and hydroxyhexahydrocannabinol (OH-HHC)) and 37 different organic compounds in the food supplement samples. The first identification of HHC-O in Slovenia was reported to the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA). The analysis of the food supplement samples revealed irregularities in 15 % of the samples. Products purchased online were particularly problematic as they contained phosphodiesterase type 5 (PDE5) inhibitors and their derivatives, as well as anorectics such as sibutramine. The developed method is a good tool for screening analysis of rapidly evolving psychoactive substances and food supplements, which are freely available online to anyone but may contain harmful or even life-threatening substances. The method allows the identification of a wide range of organic compounds and, by using solutions of standards, could also be used to determine the concentrations of these potentially hazardous compounds in samples, thus preventing potential health complications from their use

Oxidative depolymerisation of kraft lignin

The production of green hydrogen may be greatly aided by the use of an alternative anode reaction replacing oxygen evolution to increase energy efficiency and concomitantly generate value-added products. Lignin, a major component of plant matter, is accumulated in large amounts in the pulp and paper industry as waste. It has excellent potential as a source of aromatic compounds and can be transformed into the much more valuable aroma chemical vanillin by electrochemical depolymerisation. We used a flow-through model electrolyser to evaluate electrocatalyst-modified Ni foam electrodes prepared by a scalable spray-polymer preparation method for oxidative lignin depolymerisation. We demonstrate how pulsing, i. e. continuously cycling between a lower and a higher applied current, increases the amount of formed vanillin while improving the energy efficiency. Further, we present a scanning droplet cell-assisted high-throughput screening approach to discover suitable catalyst materials for lignin electrooxidation considering that a suitable electrocatalyst should exhibit high activity for lignin depolymerization and simultaneously a low activity for vanillin oxidation and oxygen evolution. Combining electrosynthesis and electrocatalysis can aid in developing new customised materials for electrochemical processes of potential industrial interest