Search

Memantine is a pharmaceutical used to treat memory loss, one of the main symptoms of dementia and Alzheimer’s disease. The use of memantine is expected to continue to grow due to the increasing proportion of the elderly population worldwide. The aim of this work was to conduct a comprehensive study on the behaviour of memantine in the environment and the possibilities of its removal from wastewater. Abiotic elimination processes (hydrolysis, photolysis and sorption) of memantine in the environment were investigated. Results showed that memantine is stable in the environment and easily leached from river sediment. Therefore, further investigation was focused on memantine removal by advanced oxidation processes that would prevent its release into the environment. For photolytic and photocatalytic degradation of memantine, ultraviolet (UV) lamps with the predominant radiation wavelengths of 365 nm (UV-A) and 254/185 nm (UV-C) were used as a source of light. TiO2 in the form of a nanostructured film deposited on the borosilicate glass wall of the reactor was used for photocatalytic experiments. Photodegradation of memantine followed pseudo-first-order kinetics. The half-life of photocatalytic degradation by UV-A light was much higher (46.3 min) than the half-life obtained by UV-C light (3.9 min). Processes degradation efficiencies and evaluation of kinetic constants were based on the results of HPLC-MS/MS analyses, which also enable the identification of memantine oxidation products. The acute toxicity of the reaction mixture during the oxidation was evaluated by monitoring the inhibition of the luminescence of Vibrio fischeri bacteria. The results showed that memantine and its oxidation products were not harmful to Vibrio fischeri.

Pharmaceuticals have special attention of researchers over the world due to their possible effect on the environment and humans. This paper focuses on the photolysis of nitrofurantoin in different water matrices. Nitrofurantoin photodegradation has been indicated as a pseudo-first order photoreaction. The indirect photodegradation rate of nitrofurantoin (river water, k1 = 0.0088 min−1 and synthetic wastewater, k1 = 0.0154 min−1) was slower than its direct photolysis rate (ultrapure water, k1 = 0.0176 min−1). The highest value of quantum yield of nitrofurantoin photodegradation (ϕ = 0.2047) was observed at pH = 4, while at higher pH-values it decreased. Furthermore, the mechanism of nitrofurantoin photodegradation is proposed. Heterocyclic ring opening and further hydrolysis, nucleophilic aromatic photosubstitution and homolytic N–N bond cleavage are suggested as three main initial processes of nitrofurantoin photodegradation. Acute toxicity study of nitrofurantoin and its photoproducts with regard to luminescence inhibition of Vibrio fischeri showed that the toxic effect of nitrofurantoin (EC50 = 4.0 mg L−1) decreases by photolysis.

U ovom tekstu razmatra se kako odabrati pufer ovisno o svrsi i kako ga pripraviti, pri čemu je navedeno nekoliko načina pripremanja puferskih otopina. Uz naglašeno nužno razumijevanje konstanti disocijacije kiselina, čitateljima se nastoji približiti ispravan način pripremanja željenih puferskih otopina. To se ponajprije odnosi na uzimanje u obzir svih faktora koji mogu utjecati na neki puferski sustav. U tekstu se zato obrađuju važni pojmovi i povezuju s njihovim primjenama u znanstvenom i inženjerskom svijetu. Također, pojašnjava se pojam kapaciteta pufera i njegova uloga, pojam ionske jakosti te na što ona utječe. Navedena su bitna svojstva koja pufer treba imati te kako produljiti trajanje puferskih otopina. Na kraju se može provjeriti što su zapravo puferi te su dani zadatci s ciljem samostalne provjere usvojenosti rješavanja računskih zadataka.

Gels formed by self-assembly of small organic molecules are of wide interest as dynamic soft materials with numerous possible applications, especially in terms of nanotechnology for functional and responsive biomaterials, biosensors, and nanowires. Four bis-oxalamides were chosen to show if electrospray ionization mass spectrometry (ESI-MS) could be used as a prediction of a good gelator and also to shed light on the gelation processes. By inspecting the gelation of several solvent, we showed that bis(amino acid)oxalamide 1 proved to be the most efficient, also being able of forming the largest observable assemblies in the gas phase. The formation of singly charged assemblies holding from one up to six monomer units is the outcome of the strong intermolecular H-bonds, particularly among terminal carboxyl groups. The variation of solvents from polar aprotic towards polar protic did not have any significant effects on the size of the assemblies. The addition of a salt such as NaOAc or Mg(OAc)2, depending on the concentration, altered the assembling. Computational analysis at the DFT level aided in the interpretation of the observed trends and revealed that individual gelator molecules spontaneously assemble to higher aggregates, but the presence of the Na+ cation disrupts any gelator organization since it becomes significantly more favorable for gelator molecules to bind Na+ cations up to the 3:1 ratio than to self-assemble, being fully in line with experimental observations reported here.

The mixture of six components (pyrethrin I and II, cinerin I and II, and jasmolin I and II) constituting natural insecticide pyrethrin is responsible for the insecticidal activity of Dalmatian pyrethrum (Tanacetum cinerariifolium /Trevir./ Sch. Bip.). In order to obtain deeper knowledge of its insecticidal potential, the extraction of mentioned components from plant samples was carried out for the first time, by matrix solid-phase dispersion. The influence of different factors such as the type of sorbent, sorbent-sample ratio, the elution solvent and its volume, addition of co-sorbent and drying agent, affecting extraction yield was evaluated. The pyrethrin components were extracted under optimized conditions: florisil (0.5 g) as the sorbent, mixed with 0.25 g of pyrethrum flower heads, 5 mL of acetone-ethyl acetate (1:1, v/v) as the elution solvent and 0.4 g of Na2SO4 as the drying agent. All six components in the extracts were qualitatively and quantitatively determined by HPLC-DAD. Analytical method provides high degree of linearity with r2≻0.9974, except for pyrethrin II (0.9961). Also, the method showed good precision (intra- and inter-day) with a relative standard deviation below 14 %, and recoveries mainly above 80 %. In order to demonstrate the applicability of the developed method, three Dalmatian pyrethrum natural populations from Croatia were analyzed.