Neonicotinoids are systemic pesticides, the use of which rapidly expanded in the 1990s. The negative consequences of their use only became apparent after a considerable delay. Today, a good part of chemical analysis is concerned with the development of methods for their determination, including some conventional separation techniques and more advanced methods such as electrochemical sensors.
As part of the experimental work, I tested the electrochemical properties of printed quasi-reference electrodes made of silver paste and printed counter electrodes made of platinum-based paste in a model solution. I tested printed working electrodes based on different carbon materials. A mixture of graphite and glass in a ratio of 75:25 proved to be optimal. Based on the results of the electrochemical measurements, a three-electrode system was prepared using the screen-printing technique, which proved to be a significant improvement over commercial carbon-based screen-printed electrodes. I optimized the type of material and the amount of deposition to modify the surface of the working electrode, with the main goal of improving the electrochemical response for the determination of neonicotinoid pesticides. For the three pesticides, I achieved good reproducibility over a wide linear range with detection limits of 2.68 – 4.40 mg/L.
In the last phase of the experimental work, I optimized the comparative method of HPLC-MS/MS, which, compared to electrochemical measurements, is much more time-consuming, and the consumption of solvents and the price are higher. Again, I achieved good repeatability over a wide linear range, while the detection limits are also quite low, at 0,12 - 86 g/L.
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