Study of the spatial redistribution of the analyte spectral emission in dc arc plasma induced by external oscillating magnetic field

Monochromatic digital imaging technique was developed for studying the spatial emission intensity distribution of atmospheric pressure dc arc plasma with aerosol supply. Arc plasma was imposed to external oscillating magnetic fields of strengths up to 12 mT and frequency of 50 Hz. This plasma was studied in a laterally resolved manner and at selected observation heights. The intensity enhancement and spatial redistribution of the analyte emission was evaluated and compared to the steady state plasma. The intensity enhancements were correlated with the attained speeds of plasma core movement. Spatial regions in the arc plasma with maximal emission enhancement are identified and clarified. The effect of the electrode polarity was also investigated.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

Effective determination of clomazone and oxyfluorfen in aqueous samples by differential pulse stripping voltammetry

Two novel types of electrochemical sensors were obtained by chemical deposition of Pt and MoO2 nanoparticles onto multi walled carbon nano tubes (MWCNT) and used for determination of frequently used pesticides clomazone and oxyfluorfen in aqueous media via differential pulse stripping voltammetry (DPSV). Clomazone was determined in 0.1 M phosphate buffer solution at pH 7.0 in the concentration range 0.61-20.56 ng cm-3, with LOQ = 0.61 and LOD = 0.38 ng cm-3. Oxyfluorfen was determined with good reproducibility (RSD <2.4%) in the concentration range 2.5-34.5 ng cm-3, with r = 0.99 and a LOQ of 1.5 ng cm-3. Results were in the same range measured by HPLC/DAD, which was used as comparative method. Structural characterization of the dopped MWCNT performed by Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron (HR-TEM), and X-ray crystallography revealed a preserved MWCNT structure decorated with well dispersed species of the platinum and MoO2 nanoparticles.IX International Scientific Conference "Technics. Technologies. Education. Safety"; June 07-10, 2021; Borovets, Bulgari

Optical emission measurement of plasma generated by infrared laser beam with Cu target

A study of visible (VIS) optical emission of Cu-plasma, induced by infrared (IR) Transversely Excited Atmospheric (TEA) CO2 laser, was carried out. Irradiation of the Cu-target with laser fluence of 8.2 J/cm2 at low air pressure resulted in the appearance of intensive plasma over the target. The type, number and intensity of the emission Cu-spectral lines strongly depend on the observing plasma location with respect to the target surface. “Primary” plasma gives the largest number of spectral lines. Also, in contrary to other plasma locations, some ionic lines were detected from this region. “Secondary” plasma, as a rule, gives the atomic lines. This region of plasma is very favourable for possible analytical applications (e.g. quantitative analysis)

Removal of cationic dye from water by activated pine cones

Adsorption of a cationic phenothyazine dye methylene blueonto activated carbon prepared from pine cones was investigated with the variation in parameters of contact time, dye concentration and pH. The kinetic data were found to follow the pseudo-second-order kinetic modelclosely. The equilibrium data were best represented by the Langmuir isotherm with maximum adsorption capacity of 233.1 mg g-1. Adsorption was favored by using a higher solution pH. Textural analysis by nitrogen adsorption was used to determine specific surface area and pore structure of the obtained carbon. Boehm titrations revealed that carboxylic groups are present in the highest degree on the carbon surface. The results indicate that the presented method for activation of pine cones could yield activated carbon with significant porosity, developed surface reactivity and considerable adsorption affinity toward cationic dye methylene blue

Analytical capability of plasma induced by IR TEA CO2 laser pulses on copper target

Spatially-resolved time-integrated optical emission spectroscopy was applied for investigation of copper plasma produced by a nanosecond Infrared (IR) Transversely Excited Atmospheric (TEA) CO2 laser, operating at 10.6 µm. The maximum intensity of emission, with sharp and well resolved spectral lines, and negligibly low background emission, was obtained from a plasma zone 8 mm from the target surface. The favorable signal to background ratio obtained in this plasma region, indicate possible analytical application of TEA CO2 produced copper plasma. Detection limits of trace elements present in the Cu sample were in the order of 10 ppm

Degradation of crystal violet over heterogeneous TiO2-based catalysts: The effect of process parameters

In this study, modified sol-gel method was employed to synthesize the pure and Zr-doped titania catalysts. Brunauer-Emmett-Teller (BET) method was applied to determine porosity, X-ray diffraction (XRD) analysis was used to study crystal structure, scanning electron microscopy (SEM) was used to investigate morphology and Fourier transform infrared spectroscopy (FTIR) was used to examine surface properties/total acidity of the obtained catalysts samples. Photocatalytic activity was tested in the reaction of crystal violet (CV) dye decolourization/degradation under UV light irradiation. The effects of several photocatalysis operational parameters were considered, such as catalyst dosage, initial dye concentrations, duration of UV irradiation treatment, as well as catalysts calcination temperatures and dopant amounts. The obtained results indicated faster dye decolourization/degradation with the increase of the catalyst dosage and the decrease of initial CV concentrations. The Zr-doping affects photocatalytic properties, i.e. CV decolourization/degradation of the prepared catalytic materials. Thus, addition of 5 wt.% of ZrO2 to titania increases photocatalytic effect for similar to 15% and addition of 10 wt.% of ZrO2 improves the photocatalytic efficiency of titania for nearly 30%

Antioxidant Activity of Grapefruit (Citrus Paradisi) Extract

Citrus fruits are widely consumed around the world and among them grapefruit (Citrus paradisi macfad) stands out with its characteristic appearance and flavor. The fruit is growing on a tree that belongs to Rutaceae family and its positive contribution to health is attributed to phytochemicals found in it. The phytochemicals have the key role in mediating oxidation process because they act as antioxidants and by that prevention of cell damage, reducing the risks of many diseases, boosting of the immune system, balancing hormone levels, and notable antibacterial and antiviral response of the organism happens. Grapefruits contain several phytochemicals including: carotenoids, flavonoids (naringin), limonoids, organic acids, pectin, and folate. Considering the worldwide consumption and popularity in everyday diet of grapefruit, the antioxidant activity of its extracts is determined in this paper. Weighed amount 10 g of fresh grapefruits was added to a mixture consisting of organic solvents (hexane, acetone, and ethanol in volumes ratio 2:1:1, respectively) and 0.05% (w/v) butylated hydroxytoluene. The mixture was stoppered and mixed on an orbital shaker at 180 rpm for 15 minutes. The temperature during the mixing was kept at 5 °C in the water bath. Afterward, 7.5 ml of cold deionized water on every 10 grams of starting sample was added to the mixture and agitated for another 5 min. The suspension was transferred to a separation funnel to separate the upper (non-polar) from the lower (polar) phase for 10 minutes at room temperature. The polar phase was subjected for antioxidant capacity determination by ABTS, DPPH, FRAP and CUPRAC methods. The results for the applied methods expressed per kg of the sample are: 1.8 mmol∙kg-1, 0.72 mmol∙kg-1, 9.7 μmol∙kg-1, 4.66 mmol∙kg-1, respectively. The obtained results are recommending grapefruit as a potent source of phytochemicals with antioxidant properties.15th International symposium „Novel technologies and sustainable development", October 20-21 2023, Leskovac

Efficient separation of Tc-99 from aqueous solution using pinecone activated carbon

Sorption of radioactive 99Tc-pertechnetate onto activated carbon prepared from pinecones was investigated. The parameters of contact time and Tc-99 concentration were varied. It was established that the sorption half-life, t1/2, was very short ~ 2.2 min, thus making this sorbent an excellent candidate for immediate pollution remediation, which is very important in the case of nuclear accidents. The kinetic data were found to follow closely the pseudosecond- order (PSO) kinetic model. Boyd model established the sorption dependence only on film diffusion. The partitioning/distribution coefficient, Kd, attained was 2729 cm3 g-1. The equilibration time was 3 h at room temperature (T=298 K)

Carotenoid and flavonoid levels, antioxidant activity and antimicrobial properties of tomato grown in Serbia

This work provides an insight into the nutritional quality of Hector-F1 tomato (Solanum lycopersicum L.) fruit grown in Serbia and the juice prepared from it regarding the contents of carotenoids, flavonoids and polyphenols as compounds beneficial for a healthy diet. Initially, ultra-high performance liquid chromatography with electrospray ionization mass spectrometry (UHPLC-ESI-MS) was employed for both polar and non-polar tomato extracts to identify compounds present in the samples. Then, lycopene, β-carotene, total polyphenols and flavonoids contents were determined by means of ultraviolet-visible (UV-Vis) spectrophotometry. To evaluate the antioxidant activity of the samples, four methods were applied, namely, the 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) method, 2,2-diphenyl-1-picrylhydrazyl (DPPH) method, the ferric ion reducing antioxidant power (FRAP) method and the cupric ion reducing antioxidant capacity (CUPRAC) method. In addition, the antimicrobial potential was tested against gram-positive bacteria, gram-negative bacteria and the yeast Candida albicans. The thermal treatment in all cases modified the chemical composition of tomato as demonstrated by a decrease in values of all measured parameters. This comprehensive analysis provided data applicable to profiling and comparing cultivars grown in different geographical regions. © 2022 National Agricultural and Food Centre (Slovakia)

Recent Advances in Electrochemical Determination of Pesticides

Widespread usage of pesticides in agricultural practice caused their residues to appear in water and food products intended for human consumption. The potential toxicity of these resources has raised awareness about pesticide tracking in the environment. Development of reliable electrochemical sensors for the on-site determination of pesticide concentrations is envisioned as an alternative to conventional chromatographic methods which are robust, expensive and require skilled work force. Modification of the working electrode surface can result in enhanced electrochemical response towards selected pesticide making such electrode convenient sensor for facile and efficient determination of pesticides in low concentrations. New generation of nanomaterials is applied in electrode modification in order to improve its sensitivity and selectivity. The present review summarizes significant advances in voltammetric detection of pesticides for the period of the past five years. The major focus of this review is set to the types of carbon and oxide based materials, metal nanoparticles, composites and other materials employed to upgrade standard electrode configurations such as glassy carbon and carbon paste electrodes, boron doped diamond electrodes, screen printed and film electrodes, metal and amalgam, and other kinds of electrodes