Corrosion inhibitition of coper by Padina pavonica (Linnaeus) Thivy extract : diploma thesis

U ovom radu ispitano je djelovanje 75 %-tnog etanolno - vodenog eksrakta smeđe alge Padina pavonica (u volumenskim koncentracijama 0,2 % , 0,8 %, 1,4 % i 2,0 % ) kao inhibitora korozije bakra u 0,5 mol dm -3 otopini NaCl. Pri istraživanju su korištene elektrokemijske metode: potencijal otvorenog kruga, metoda linearne polarizacije i metoda potenciodinamičke polarizacije. Nakon provedenih polarizacijskih mjerenja napravljena je analiza površine uzoraka pretražnim elektronskim mikroskopom čime su potvrđeni rezultati dobiveni elektrokemijskim mjerenjima. Za najbolju volumensku koncentraciju inhibitora, 1,4 % (koja je određena u ovom radu) ispitana je korozija u temperaturnom području od 273 do 303 K. Korištenjem adsorpcijskih izotermi (Freundlichove i Frumkinove) određen je mehanizam adsorpcije inhibitora na površinu bakra, tj. rezultati potvrđuju da se radi o fizisorpciji.This paper aims to study the inhibition effect of aqueous ethanol 75 % extract of brown algae Padina pavonica (in 0.2 %, 0.8 %, 1.4 % and 2.0 % (v/v) concentration) on corrosion of copper in the 0.5 mol dm –3 NaCl solution by electrochemical techniques such as open circuit potential, linear polarization, and potentiodynamic polarization technique. Additionally, a characterization of the metal surface with scanning electron microscope (SEM). The data demonstrated that the highest protection was obtained at the algae extract concentration of 1.4 % v/v. The SEM analysis gave very good support to the electrochemical data. Also, the temperature influence was studied in the range 283 – 303 K. The adsorption of Padina Pavonica on copper surface was in accordance with the Freundlich and Frumkin adsorption isotherms. Results confirm physical adsorption of this inhibitor on the copper

Seasonality of Polyaromatic Hydrocarbons (PAHs) and Their Derivatives in PM_2.5 from Ljubljana, Combustion Aerosol Source Apportionment, and Cytotoxicity of Selected Nitrated Polyaromatic Hydrocarbons (NPAHs)

Airborne particulate matter (PM) is a vector of many toxic pollutants, including polyaromatic hydrocarbons (PAHs) and their derivatives. Especially harmful is the fine fraction (PM2.5), which penetrates deep into the lungs during inhalation and causes various diseases. Amongst PM2.5 components with toxic potential are nitrated PAHs (NPAHs), knowledge of which is still rudimentary. Three of the measured NPAHs (1-nitropyrene (1-nP), 9-nitroanthracene (9-nA), and 6-nitrochrysene (6-nC)) were detected in ambient PM2.5 from Ljubljana, Slovenia, along with thirteen non-nitrated PAHs. The highest concentrations of pollutants, which are closely linked with incomplete combustion, were observed in the cold part of the year, whereas the concentrations of NPAHs were roughly an order of magnitude lower than those of PAHs throughout the year. Further on, we have evaluated the toxicity of four NPAHs, including 6-nitrobenzo[a]pyrene (6-nBaP), to the human kidney cell line, HEK293T. The most potent was 1-nP (IC50 = 28.7 µM), followed by the other three NPAHs, whose IC50 was above 400 or 800 µM. According to our cytotoxicity assessment, atmospheric 1-nP is the most harmful NPAH among the investigated ones. Despite low airborne concentrations of NPAHs in ambient air, they are generally considered harmful to human health. Therefore, systematic toxicological assessment of NPAHs at different trophic levels, starting with cytotoxicity testing, is necessary in order to accurately evaluate their threat and adopt appropriate abatement strategies

The Essential Oil Composition of Helichrysum italicum (Roth) G. Don: Influence of Steam, Hydro and Microwave-Assisted Distillation

Helichrysum italicum (Roth) G. Don (Asteraceae), also known as immortelle, usually grows in the Mediterranean area. The composition of the essential oil (EO) of immortelle is a mixture of various aromatic substances, mainly monoterpenes and sesquiterpenes. Distillation is the most widely used method for extraction of EO immortelle, although the yield is very low (<1%). In this work, we aim to investigate how the use of different distillation methods affects the yield and chemical composition of immortelle EO. For this purpose, we applied two conventional methods: steam distillation (SD) and hydrodistillation (HD), and a modern (environmentally friendly) technique—microwave-assisted distillation (MAD). Wild immortelles from four different locations in Croatia were collected and carefully prepared for extraction. Each sample was then analyzed by gas chromatography–mass spectrometry (GC-MS). GraphPad Prisma statistical software was used to study the statistics between different groups of connections and analyze the data on the number of connections. The results show that HD gives a significantly higher yield (0.31 ± 0.09%) compared to MAD (0.15 ± 0.03%) and SD (0.12 ± 0.04%). On the other hand, the highest number of chemical compounds was identified with MAD (95.75 ± 15.31%), and most of them are subordinate compounds with complex structures. SD isolated EOs are rich in derived acyclic compounds with the highest percentage of ketones. The results show that the application of different distillation methods significantly affects the composition of the obtained immortelle EO, considering the yield of EO, the number of isolated, derived and non-derived compounds, chemotypes and compounds with simple (acyclic) and complex structures

The Essential Oil Composition of <i>Helichrysum italicum</i> (Roth) G. Don: Influence of Steam, Hydro and Microwave-Assisted Distillation

Helichrysum italicum (Roth) G. Don (Asteraceae), also known as immortelle, usually grows in the Mediterranean area. The composition of the essential oil (EO) of immortelle is a mixture of various aromatic substances, mainly monoterpenes and sesquiterpenes. Distillation is the most widely used method for extraction of EO immortelle, although the yield is very low (<1%). In this work, we aim to investigate how the use of different distillation methods affects the yield and chemical composition of immortelle EO. For this purpose, we applied two conventional methods: steam distillation (SD) and hydrodistillation (HD), and a modern (environmentally friendly) technique—microwave-assisted distillation (MAD). Wild immortelles from four different locations in Croatia were collected and carefully prepared for extraction. Each sample was then analyzed by gas chromatography–mass spectrometry (GC-MS). GraphPad Prisma statistical software was used to study the statistics between different groups of connections and analyze the data on the number of connections. The results show that HD gives a significantly higher yield (0.31 ± 0.09%) compared to MAD (0.15 ± 0.03%) and SD (0.12 ± 0.04%). On the other hand, the highest number of chemical compounds was identified with MAD (95.75 ± 15.31%), and most of them are subordinate compounds with complex structures. SD isolated EOs are rich in derived acyclic compounds with the highest percentage of ketones. The results show that the application of different distillation methods significantly affects the composition of the obtained immortelle EO, considering the yield of EO, the number of isolated, derived and non-derived compounds, chemotypes and compounds with simple (acyclic) and complex structures