No abstract

The most important experimental parameters of the flow potentiometric stripping analysis (PSA) with oxygen as an oxidant were investigated and optimised. A simple, homemade flow system consisting of glassy carbon tubes, which served as a working and auxiliary electrode, was used. By applying a rest period before the stripping step (the flow stop mode) and by imposing a constant reductive current simultaneously with the interruption of potentiostatic control, significant increase of the flow PSA sensitivity was achieved. In the determination of cadmium and lead, quantitation limits of 0.11 and 0.82 μg/L were obtained. The precision of the method was evaluated in terms of repeatability and reproducibility, with values of relative standard deviation lower than 4.0% for cadmium and 4.2% for lead. This modified technique was applied for simultaneous determination of cadmium and lead in milk, after a simple pretreatment of the samples by dilution and acidification. The method accuracy was confirmed by analysing the certified reference material of skimmed milk powder (ERM-BD151).

This study compares different methods for the removal of oxygen from the solution prior to the chronopotentiometric determination of the insecticide imidacloprid on glassy carbon electrode. The research included the application of the chemical method involving addition of sulfite ion, and the physical method of purging the sample with nitrogen stream, as well as their combination. By comparing analytical signals of imidacloprid, chemical method showed almost the same efficiency as conventional physical method, while the best reproducibility was achieved by applying chemical method with addition of the saturated sodium sulfite solution. The method is very simple and can be applied for deoxygenation of the solution prior to the chronopotentiometric analysis. The application of the chemical deoxygenation significantly shortened duration of the chronopotentiometric analysis of imidacloprid from approximately 15 min to 1 min. [Projekat Ministarstva nauke Republike Srbije, br. III 46009]

Nowadays various industrial and urban activities are resulting in discharging of enormous quantities of various pollutants and their accumulation in the environment. Considering that the presence of heavy metals in wastewater is a serious threat to the environment and human health and that conventional methods for their removal are not highly efficient, the current study mainly focuses to estimate cyanobacterial capability to accumulate different heavy metals from water and compare bioaccumulation and biosorption processes. Cyanobacteria Nostoc sp. was used and five heavy metals were selected for this experiment (Cd2+, Cu2+, Pb2+, Ni2+, Zn2+). Examined concentrations of HMs were 20, 80 and 200 mg/dm3 for the bioaccumulation study while for biosorption experiments 20 and 80 mg/dm3 of each HMs were used. Living cells of Nostoc sp. have the highest affinity for Pb2+ (98.15%) and Cu2+ (95.14%) removal from the solution by bioaccumulation. During the biosorption process, dried biomass of Nostoc sp., besides Pb2+ (92.27%) and Cu2+ (96.00%), shows a high affinity for Cd2+ (91.00%) removal. Living cyanobacterial cells of Nostoc sp. was capable to accumulate 82% of Zn, while dried biomass adsorbs 87% of Zn2+. The highest bioaccumulation of Ni2+ was only 38% while using the process of biosorption it was significantly higher (63.80%). These results could provide a preliminary study for further investigation in the direction of the development of immobilized biosorbents which could be used for industrial effluent treatment.

Lettuce is one of the most common types of leafy vegetables in human diet that is grown worldwide. Narrow and very small seeds make its sowing very difficult, requiring a lot of time and labour. Also, plants produced by manual sowing are often characterized by uneven germination. Those problems could be prevented by sowing pelleted seeds which require the development of adequate pelleting technology. Absence of quality lettuce seeds in the Serbian market results in large amounts of imported pelleted seeds every year. The aim of this study was to develop a domestic pelleting procedure and examine its effects on seeds quality parameters, in order to provide seeds to local farmers at a more affordable price compared to imported commercial pelleted seeds. Pelleted and non-pelleted seeds of the Panukia F1 hybrid were compared in several quality characteristics (1000 seed weight, germination energy, germination percentage, seedling length) in laboratory and greenhouse conditions. There was no loss in seed quality with the pelleting process, although the seed weight increased 12-19 times. Pelleted lettuce seeds had very high germination energy and seed germination (97-98%). In greenhouse conditions, non-pelleted seeds sprouted unevenly in relation to pelleted seeds. These results confirm the advantages of sowing pelleted seeds in terms of uniform germination and development of lettuce plants, primarily due to the precision of mechanical sowing. By offering domestic pelleting lettuce seeds to the growers, the production process would be significantly improved and accelerated with the reduction of manual labour, and therefore the overall production cost.