Optimizacija elektrokemijskega senzorja za določanje neonikotinoidov

Kovačević, Marija (author), Prosen, Helena (mentor), Kuščer, Danjela (comentor)

Neonikotinoidi predstavljajo pomembno skupino insekticidov in so strupeni za žuželke in nekatere nevretenčarje. Poleg tega predstavljajo resno grožnjo populacijam čebel, saj zmanjšujejo njihove reproduktivne sposobnosti, vplivajo na njihovo sposobnost zbiranja hrane in zmanjšujejo njihove kognitivne funkcije. Določeni neonikotinoidi so v Evropski uniji prepovedani že od leta 2018. Zato je zaznavanje teh spojin izjemno pomembno. Elektrokemični senzorji so zaželeni zaradi svoje stroškovne učinkovitosti, preprostosti, hitrega odziva in visoke občutljivosti v primerjavi s tradicionalnimi metodami. Cilj mojega magistrskega dela je bil razviti učinkovit elektrokemični senzor na osnovi tiskanih elektrod (SPE) za zaznavanje izbranih neonikotinoidov, in sicer imidakloprida, tiametoksama in klotianidina. Začetni poskusi so potekali z uporabo komercialnih SPE z delovno elektrodo na osnovi ogljika, da bi raziskali reakcijski mehanizem in določili najboljše pogoje za nadaljnje teste. Kapacitivni tok je bil nižji v čistem 0,1 M PBS v primerjavi z dodatkom organskega topila. Z dušikom nasičene raztopine so privedle do večjega redukcijskega toka za analite. Optimalni pH raztopine je 7. Redukcijski proces vključuje enako število protonov in elektronov. Med preiskavo časa akumulacije smo opazili povečanje višine toka v prvih 8–12 min, nato pa se je tokovni signal ustalil. Poleg tega je povečanje temperature privedlo do sorazmernega dviga toka. V drugem nizu poskusov smo uporabili SPE izdelane na IJS. V cikličnem voltamogramu smo opazili dva ostra vrhova z intenzitetami med 250–450 μA, kar kaže na kontaminacijo. Uporabili smo različne elektrokemične postopke predobdelave. Vrhovi so izginili po 15 ciklih v 0,1 M H2SO4 med -0,6 in +2,0 V. V zadnjem sklopu eksperimentov smo želeli ugotoviti, ali dodatna modifikacija elektrod lahko poveča signal. Ugotovili smo, da nobena od uporabljenih modifikacij ni izboljšala elektrokemičnega signala za naše analite v primerjavi z meritvami po predobdelavi.

• Language: Slovenian
• Keywords: neonikotinoidi, SPE, ciklična voltametrija, senzor
• Work type: Master's thesis/paper
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2024
• PID: 20.500.12556/RUL-158842
• Publication date in RUL: 21.06.2024

Secondary language

• Language: English
• Title: Optimization of electrochemical sensor for neonicotinoid determination

Abstract

Neonicotinoids (NNIs) represent a significant group of insecticides and are poisonous to insects and some invertebrates. Furthermore, they present a serious threat to bee populations, as they impair bees' reproductive abilities, interfere with their ability to gather food, and reduce their cognitive functions. Certain neonicotinoids have been banned in the European Union since 2018. Therefore, detecting these compounds is of crucial importance. Electrochemical sensors are preferred due to their cost-effectiveness, simplicity, fast response, and high sensitivity compared to traditional methods. The aim of my master thesis was to develop an effective electrochemical sensor based on screen-printed electrodes (SPE) for detection of selected neonicotinoids, namely: imidacloprid (IMI), thiamethoxam (TMX) and clothianidin (CLO). The initial experiments were carried out using commercial SPE with carbon working electrode (WE), aiming to investigate the reaction mechanism and determine the best conditions for subsequent analysis. The capacitive current was found to be lower in pure 0.1 M PBS than with the addition of an organic solvent. Nitrogen-saturated solutions resulted in a higher reduction current for the analytes. The solution's optimal pH was established at 7. The reduction process involves an equal number of protons and electrons. During the examination of accumulation time, a rise in the peak current height was observed for the first 8–12 min, after which it plateaued. Additionally, an increase in temperature led to a corresponding rise in current. In the second set of experiments, we used SPE made at JSI. In the cyclic voltammogram, two sharp peaks with intensities between 250–450 μA were observed, indicating contamination. Various electrochemical pretreatment procedures were applied. The peaks disappeared after 15 cycles in 0.1 M H2SO4 between -0.6 and +2.0 V. In the last part of the experiment, we wanted to see if further modification of electrodes can lead to enhancement of signal. However, none of the modifications we applied improved the electrochemical signal for our analytes compared to the measurements after pretreatment.

• Keywords: neonicotinoids, SPE, cyclic voltammetry, sensor