Volatile organic compounds from Centaurium erythraea Rafn (Croatia) and the antimicrobial potential of its essential oil

GC and MS were used for the analysis of Croatian Centaurium erythraea Rafn essential oil (obtained by hydrodistillation) and headspace (applying headspace solid-phase microextraction). The headspace contained numerous monoterpene hydrocarbons (the major ones were terpinene-4-ol, methone, p-cymene, γ-terpinene and limonene). Oxygenated monoterpenes were present in the headspace and oil, while 1,8-cineole, bornyl acetate and verbenone were present only in the headspace. High headspace percentages of toluene and naphthalene were found, followed by hemimellitene. Lot of similarities were observed with Serbian C. erythraea oil [neophytadiene (1.4%), thymol (2.6%), carvacrol (6.1%) and hexadecanoic acid (5.7%)], but different features were also noted such as the presence of menthol, menthone and phytone. The oil fractionation enabled identification of other minor compounds not found in total oil such as norisoprenoides, alk-1-enes or chromolaenin. The essential oil showed antimicrobial potential on Escherichia coli, Salmonella enteritidis, Staphylococcus aureus and Bacillus cereus. On the other hand, no antibacterial activity of the oil was observed on Pseudomonas fluorescens and Lysteria monocytogenes.     

Study of carbon black obtained by pyrolysis of waste scrap tyres

Waste scrap tyres were thermally decomposed under various conditions. Decompositions were followed by the TGA method. Specific heating regimes were tested to obtain optimal structural properties of resulting pyrolytic carbon black produced by pyrolysis of scrap tyres and the process was characterized in temperature interval from 380 to 1,200 °C and heating rate 10, 20 and 50 °C min^?1 under nitrogen atmosphere. The original scrap tyres and pyrolytic carbon black were characterized by Raman and Fourier transform infrared spectroscopy methods. Textural properties were also determined. Effect of temperature and heating rate on process of pyrolysis of scrap tyres was observed. Shifting of temperature of maximum pyrolysis rate to lower value and spreading of DTG peak is caused by increasing heating rate. Temperature 570 °C was sufficient for total scrap tyres pyrolysis. Graphitic and disordered structure was distinguished in the formed carbon black by Raman spectroscopy. With increasing temperature, heating rate and weight loss, the amount of the graphitic structure was reduced at the expense of disordered structure. Destruction of nonporous scrap tyres and formation of porous structure took place at higher temperature. Porous carbon black is formed above 380 °C, specific surface area increased up to 88 m² g^?1 .     

Optimization of SPME-Arrow-GC/MS Method for Determination of Free and Bound Volatile Organic Compounds from Grape Skins

(1) Background: Solid phase microextraction (SPME)-Arrow is a new extraction technology recently employed in the analysis of volatiles in food materials. Grape volatile organic compounds (VOC) have a crucial role in the winemaking industry due to their sensory characteristics of wine.; (2) Methods: Box–Behnken experimental design and response surface methodology were used to optimise SPME-Arrow conditions (extraction temperature, incubation time, exposure time, desorption time). Analyzed VOCs were free VOCs directly from grape skins and bound VOCs released from grape skins by acid hydrolysis.; (3) Results: The most significant factors were extraction temperature and exposure time for both free and bound VOCs. For both factors, an increase in their values positively affected the extraction efficiency for almost all classes of VOCs. For free VOCs, the optimum extraction conditions are: extraction temperature 60 °C, incubation time 20 min, exposure time 49 min, and desorption time 7 min, while for the bound VOCs are: extraction temperature 60 °C, incubation time 20 min, exposure time 60 min, desorption time 7 min.; (4) Conclusions: Application of the optimized method provides a powerful tool in the analysis of major classes of volatile organic compounds from grape skins, which can be applied to a large number of samples.     

Green chromatography separation of analytes of greatly differing properties using a polyethylene glycol stationary phase and a low-toxic water-based mobile phase

A simple, rapid, and environmentally friendly HPLC method was developed and validated for the separation of four compounds (4-aminophenol, caffeine, paracetamol, and propyphenazone) with different chemical properties. A “green” mobile phase, employing water as the major eluent, was proposed and applied to the separation of analytes with different polarity on polyethylene glycol (PEG) stationary phase. The chromatography separation of all compounds and internal standard benzoic acid was performed using isocratic elution with a low-toxicity mobile phase consisting of 0.04 % (v/v) triethylamine and water. HPLC separation was carried out using a PEG reversed-phase stationary phase Supelco Discovery HS PEG column (15?×?4 mm; particle size 3 μm) at a temperature of 30 °C and flow rate at 1.0 mL min^?1. The UV detector was set at 210 nm. In this study, a PEG stationary phase was shown to be suitable for the efficient isocratic separation of compounds that differ widely in hydrophobicity and acid–base properties, particularly 4-aminophenol (log P, 0.30), caffeine (log P, ?0.25), and propyphenazone (log P, 2.27). A polar PEG stationary phase provided specific selectivity which allowed traditional chromatographic problems related to the separation of analytes with different polarities to be solved. The retention properties of the group of structurally similar substances (aromatic amines, phenolic compounds, and xanthine derivatives) were tested with different mobile phases. The proposed green chromatography method was successfully applied to the analysis of active substances and one degradation impurity (4-aminophenol) in commercial preparation. Under the optimum chromatographic conditions, standard calibration was carried out with good linearity correlation coefficients for all compounds in the range (0.99914–0.99997, n?=?6) between the peak areas and concentration of compounds. Recovery of the sample preparation was in the range 100?±?5 % for all compounds. The intraday method precision was determined as RSD, and the values were lower than 1.00 %.

Determination of 129I in biomonitors collected in the vicinity of a nuclear power plant by neutron activation analysis

Neutron activation analysis (NAA) was used to determine ¹²⁹I and the ¹²⁹I/¹²⁷I ratio in bovine thyroid, moss, and river sediment samples collected in the vicinity of the Temelín nuclear power plant (NPP) in south Bohemia. The NAA procedures comprised pre-irradiation separation of ¹²⁹I by combustion of the samples in the stream of oxygen at 1,000 °C and trapping the liberated iodine in a LiOH/(NH₄)₂SO₃ solution. Post-irradiation separation of ¹³⁰I produced by the reaction ¹²⁹I(n,γ)¹³⁰I was carried out by extraction of elementary iodine with chloroform followed by precipitation of PdI₂. Nondestructive, epithermal NAA was used to determine ¹²⁷I employing the ¹²⁷I(n,γ)¹²⁸I reaction. The results showed that mean values of ¹²⁹I and the ¹²⁹I/¹²⁷I ratio in the bovine thyroids varied from 22 to 61 mBq kg^?1 (dry mass) and 2.8 × 10^?9 to 5.4 × 10^?9, respectively. These values are close to the lower end of results reported from various regions non-polluted with ¹²⁹I. No significant differences were found between ¹²⁹I concentrations and the ¹²⁹I/¹²⁷I ratios in the bovine thyroids collected prior to the start and after several years of operation of the NPP. The mean value and standard deviation of ¹²⁹I in mBq kg^?1, dry mass and the ¹²⁹I/¹²⁷I ratio in moss Pleurozium schreberi were 23 ± 16 and 2.3 × 10^?9, respectively, whereas values of ¹²⁹I in the river sediments were below 8–10 mBq kg^?1 (dry mass) after several years of the NPP operation.     

2,8'-disubstituted-1,1'-binaphthyls: a new pattern in chiral ligands

The title binaphthyls 19 and 26, which are the positional isomers of 2-methoxy-2'-(diphenylphosphino)-1,1'-binaphthyl (MOP, 19) and 2-amino-2'-hydroxy-1,1'-binaphthyl (NOBIN, 26), have been synthesized by Suzuki coupling as the key step (10 + 15-->18), followed by functional group transformations, involving C-P and C-N bond formation (18-->19 and 18-->23). Racemic intermediate 22 was resolved by co-crystallization with N-benzylcinchonidinium chloride and the absolute configuration determined by X-ray crystallography. These novel binaphthyls are configurationally stable and, as such, potentially usable as chiral ligands in asymmetric reactions. Michael addition of the glycine-derived enolate 40 to methyl acrylate, carried out in the presence of (R)-(-)-27 as the chiral phase-transfer catalyst, afforded L-glutamic acid (S)-(+)-43 of 92% ee (after hydrolysis of the primary product).     

History dependent structural properties of alumina-supported nickel oxide

The formation of nickel oxide from Ni–Al takovite-like compounds has been investigated. Information about the stoichiometry of the NiO phase obtained by Diffuse Reflectance (DR) spectroscopy is discussed in connection with TPR and solubility data.