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Different sensitivity of various types of DNA to damage and mutation requires a study of effects of chemical and physical factors on integrity of individual DNA structures. Oxidation stress induced by photoactivated nanoparticles including quantum dots is considered to be the main mechanism of their potential risks. In this work, spectrophotometric indicators of reactive oxygen species (ROS) 4‐chloro‐7‐nitrobenzo‐2‐oxa‐1,3‐diazole (NBD−Cl) and α‐diphenyl‐β‐picrylhydrazyl (DPPH), electrochemical DNA‐based biosensors with the thiol‐capped CdS quantum dots (CdS QDs) immobilized over the chromosomal (ct DNA) and plasmid (pUC19) DNA biorecognition layers and agarose gel electrophoresis were used (i) to detect ROS generated at the UV‐C irradiation (λ=254 nm) of CdS QDs and (ii) to assess and evaluate their effect towards the chromosomal and plasmid dsDNA structure. Voltammetric and impedimetric measurements revealed a deep degradation of DNA attached to the glassy carbon electrode surface with a stepwise decrease of the portion of survived pUC19 and ct DNA after 60 s to 2400 s irradiation time up to 47 % and to 32 %, resp., comparing to the portion in the absence of CdS QDs reaching 58 % and 40 %, resp. Agarose gel electrophoresis supported the damage to plasmid and chromosomal DNA demonstrating double strand breaks. A decrease in the stability of DNA types towards degradation by ROS in order pUC19>calf thymus>salmon sperm dsDNA has been found.

Voltammetric techniques have been considered as an important analytical tool applied to the determination of trace concentrations of many biological molecules including ascorbic acid. In this paper, ascorbic acid was detected by square wave voltammetry, using graphene oxide paste as a working electrode, modified by a film of a manganese(II) complex compound. Various factors, such as the effect of pH, affecting the response characteristics of the modified electrode were investigated. The relationship between the peak height and ascorbic acid concentration within the modified working electrode was investigated, using the calibration graph. The equation of the calibration graph was found to be: I = 0.0550γac + 0.155 with R2 = 0.9998, where I is the SWV current and γac is the mass concentration of ascorbic acid. The LOD and LOQ of the proposed method were determined to be 1.288 μg/L and 3.903 μg/L, respectively. Several compounds, such as riboflavin, biotin, and ions, such as Fe and Cu, were tested and it seemed that they did not interfere with the analytic signal. The proposed procedure was successfully applied in the determination of ascorbic acid in Rosa canina hips.

Oligomers are a particular category of non-intentionally added substances (NIAS) that may be present in food contact materials (FCMs), such as polyethylene terephthalate (PET), and consequently migrate into foods. Here, an ultra-high-pressure liquid chromatography quadruple time-of-flight mass spectrometry (UHPLC-qTOF-MS) method was developed for the analysis of 1st series cyclic PET oligomers in virgin olive oil (VOO) following a QuEChERS clean-up protocol. Oligomer migration was evaluated with two different migration experiments using bottles from virgin and recycled PET: one with VOO samples stored in household conditions for a year and one using the food simulant D2 (95% v/v ethanol in water) at 60 °C for 10 days. Calibration curves were constructed with fortified VOO samples, with the LOQs ranging from 10 to 50 µg L−1 and the recoveries ranging from 86.6 to 113.0%. Results showed no migration of PET oligomers in VOO. However, in the simulated study, significant amounts of all oligomers were detected, with the migration of cyclic PET trimers from recycled bottles being the most abundant. Additional substances were tentatively identified as linear derivatives of PET oligomers. Again, open trimer structures in recycled bottles gave the most significant signals.

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