1. Dimethoate detection through a fluorescent coumarin dyeEdoardo Donà, Gerhard J. Mohr, Aleksandra Lobnik, 2024, original scientific article Abstract: In this study, we present a straightforward and innovative approach utilizing a coumarin fluorescent dye for the detection of dimethoate in green tea. Initially, the pesticide undergoes hydrolysis in a NaOH solution, yielding our target analyte, methylamine. Following neutralization to pH 9, methylamine reacts with the dye in CH3CN for 20 min. After a careful optimization, we achieved an outstanding linear correlation (R2 = 0.999) for dimethoate, spanning concentrations from 7.8 to 292 µg/L and LOD of 3.2 µg/L. Moreover, we successfully detected dimethoate in green tea, with a recovery of 95.4% (σ = 5.7%). Organophosphates pesticides (OPs), which dimethoate is one of the most used, pose a significant threat due to their toxicity upon both high direct exposure and prolonged low-level exposure, which has been linked to cancer. Therefore, the development of a detection method that is both selective and sensitive is imperative for safeguarding both the population and the environment. This method effectively addresses the stability challenges encountered by enzyme-based fluorescent sensors, thereby opening new avenues for the detection of organophosphate pesticides.
Keywords: organophosphate pesticide, methylamine, coumarin, fluorescence detection, dimethoate, TICT, twisted intramolecular charge transfer
Published in DKUM: 20.12.2024; Views: 0; Downloads: 2
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2. The use of a novel smartphone testing platform for the development of colorimetric sensor receptors for food spoilageTinkara Mastnak, Gerhard J. Mohr, Matjaž Finšgar, 2023, original scientific article Abstract: This work presents a novel smartphone testing platform for the validation of colorimetric sensor receptors (CSRs) in the form of layers that enables reliable and straightforward determination of their color change in a closed system using a commercially available color sensor. The food-compatible model CSR used for the method development was made of black carrot extract and ethyl cellulose. The colorimetric responses were studied in detail for NH3, dimethylamine (DMA), and trimethylamine (TMA) by analyzing changes in the value of the total color difference (ΔE) with the increasing logarithm of the mass concentration (log γ) of the analytes. The method was partially validated for the detection limit (LOD), the limit of quantification, sensitivity, and linear γ range. The fastest reaction times were obtained for the NH3 analyte, while the calculated LOD values were quite similar (1.48 mg L−1 for NH3, 1.55 mg L−1 for DMA, and 1.58 mg L−1 for TMA). The applicability of CSRs was shown for different types of muscle food. Frozen (boneless and skinless) hake fillets were used for additional experimental work in which the color changes of the CSRs were correlated with the values of the total volatile basic nitrogen (TVB-N) and the total counts of aerobic and anaerobic microorganisms. The developed testing platform shows great promise for the development of CSRs that define the quality of a broad variety of muscle food.
Keywords: sensors receptors, CSRs, colorimetric
Published in DKUM: 01.08.2023; Views: 781; Downloads: 46
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3. Design and characterization of dicyanovinyl reactive dyes for the colorimetric detection of thiols and biogenic aminesTinkara Mastnak, Aleksandra Lobnik, Gerhard J. Mohr, Matejka Turel, 2018, original scientific article Keywords: indicator dye, chromoreactand, absorption, thiols, biogenic amines
Published in DKUM: 08.03.2018; Views: 1855; Downloads: 384
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4. Sol-gel-based optical sensor for the detection of aqueous aminesŠpela Korent Urek, Aleksandra Lobnik, Gerhard J. Mohr, 2007, original scientific article Abstract: We present an optical sensor for the detection of aqueous amines obtained by incorporating chromoionophore XV (ETHT 4001) into sol-gel thin films. Acid- and base-catalyzed sol-gel processes were studied to prepare stable ormosil layers using various amounts of organically modified sol-gel precursor such asmethyltriethoxysilane (MTriEOS). The sensor layers were coated with a protective layer of microporous white polytetrafluoroethylene (PTFE) in order to prevent interference from ions and ambient light. The measurements were carried out in a flow-through cell in the reflection mode. Acid-catalyzed ormosil layers (pH 1) based on the copolymerization of tetraethoxysilane (TEOS) and MTriEOS did not show any change in signal upon exposure to aqueous amine solutions, while base-catalyzed sensor layers (pH 3 and 13) showed significant changes in signal. The response time (t100) for the base-catalyzedsensor layer L3 (pH 13) upon exposure to different solutions containing 0-608 mmol L-1 aqueous propylamine was 20-30 s, the regeneration time was 70 s and the detection limit was 0.1 mmol L-1. The sensor response was reproducible and reversible. The porous ormosil layers permit dry sensor storage conditions.
Keywords: analytical chemistry, optical sensors, sol-gel technology, determination of amines, fluorimetry
Published in DKUM: 01.06.2012; Views: 3256; Downloads: 94
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