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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.

Pyrethrin is a potent biopesticide, a natural mixture of six compounds (pyrethrin I and II, cinerin I and II, and jasmolin I and II), biosynthesized in plants of Dalmatian pyrethrum (Tanacetum cinerariifolium/Trevir./Sch. Bip.), a species endemic to the eastern Adriatic coast, but grown worldwide. Not many known natural insecticides encompass such superior qualities as pyrethrin—very high efficacy against a broad spectrum of pests in combination with minor adverse effects on human health and the environment. In previous decades, pyrethrin was largely replaced by its synthetic derivatives, pyrethroids. However, due to their harmful effects on various species and ecosystems, the use of pyrethrin should again take the lead. This review summarizes one century (1920–2020) of research on the properties and use of pyrethrum as a source of pyrethrins. The primary focus is on presenting its current advantages and disadvantages, toxicity on target and non-target species, biosynthesis, factors that influence the pyrethrins content in pyrethrum, comparison of different methods of their extraction and determination ; as well as its production potential and development of new products. The final goal is to present possible approaches to improve and enhance the use of this highly effective but still underused phytochemical insecticide with unique properties.

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.

Puferi su važni za mjerenje i održavanje vrijednosti pH koje je ključno u mnogobrojnim svakodnevnim znanstvenim i industrijskim djelatnostima. Stoga, cilj ovoga teksta je razjasniti fizikalno-kemijske parametre na kojima počivaju puferi. Obrađeno je kako se i zašto provodi umjeravanje članka za mjerenje pH. Navedeno je koji se problemi mogu pojaviti tijekom mjerenja pH i kako te probleme riješiti. Rad se bavi primjenom stečenog znanja u nastavi, kao i njihovom provjerom kroz primjere i računske zadatke. Navedenim praktičnim primjerima olakšano je usvajanje temeljnih pojmova vezanih uz pH i pufere. Tako je obrađeno kako pravilno definirati pH, što je Henderson-Hasselbalchova jednadžba i koja su joj ograničenja, kako vizualno provjeriti djelovanje pufera, koja je povezanost Le Chatelirova načela i pufera, o čemu treba voditi računa prilikom mjerenja pH. Među ostalim, navedena je i važnost utjecaja temperature kod umjeravanja pH-članka, mjerenja pH uzorka, ali i iskazivanja vrijednosti pH. Na kraju, navedeno je kako unaprijediti stečena znanja i vještine kroz pitanja povezana s vrijednostima pH i puferima. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna., Buffers are of high importance for pH measurement and control, which is crucial in many everyday scientific and industrial activities. The aim of this article was to elucidate the physicochemical parameters of buffers. Explained are the process and background of pH electrode calibration, as are described the problems that may arise in pH measurement, and their solutions. The focus of this article is the application and assessment of this knowledge in education through examples and numerical problems. The practical examples facilitate the learning of basic concepts related to pH and buffers. We clarify the correct definition of pH value, the Henderson-Hasselbalch equation and its limitations, the use of visual indicators with buffers, the connection between Le Chatelier’s principle and buffers, and what is important in pH measurement. A special mention is given to the influence of temperature in pH electrode calibration, pH measurement, and expressing the pH value. Finally, we suggest how to further improve the students’ knowledge and skills through questions on problems related to pH value and buffers. This work is licensed under a Creative Commons Attribution 4.0 International License.

Pharmaceuticals as ubiquitous organic pollutants in the aquatic environment represent substances whose knowledge of environmental fate is still limited. One such compound is metoclopramide, whose direct and indirect photolysis and toxicological assessment have been studied for the first time in this study. Experiments were performed under solar radiation, showing metoclopramide as a compound that can easily degrade in different water matrices. The effect of pH-values showed the faster degradation at pH = 7, while the highly alkaline conditions at pH = 11 slowed photolysis. The highest value of quantum yield of metoclopramide photodegradation (ϕ = 43.55·10−4) was obtained at pH = 7. Various organic and inorganic substances (NO3−, Fe(III), HA, Cl−, Br−, HCO3−, SO42−), commonly present in natural water, inhibited the degradation by absorbing light. In all experiments, kinetics followed pseudo-first-order reaction with r2 greater than 0.98. The structures of the photolytic degradation products were tentatively identified, and degradation photoproducts were proposed. The hydroxylation of the aromatic ring and the amino group's dealkylation were two major photoproduct formation mechanisms. Calculated thermochemical quantities are in agreement with the experimentally observed stability of different photoproducts. Reactive sites in metoclopramide were studied with conceptual density functional theory and regions most susceptible to •OH attack were characterized. Metoclopramide and its degradation products were neither genotoxic for bacteria Salmonella typhimurium in the SOS/umuC assay nor acutely toxic for bacteria Vibrio fischeri.

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. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna., The text discusses how to choose buffers depending on the purpose, and how to prepare them in several ways. With the necessary understanding of acid dissociation constants and buffer mechanisms, it is meant to give the readers the correct approach when preparing desired buffer solutions by taking into account all factors that may affect the buffer system. Therefore, the text covers important concepts, and links them with their applications in the world of science and engineering. It also explains buffer capacity and its role, as well as the concept of ionic strength and how it affects the pH. At the end, explanations of buffers are summarized and some numerical problems are given to enable self-evaluation of the comprehension of the given subject. This work is licensed under a Creative Commons Attribution 4.0 International License.

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 increased utilization of one-dimensional (1D) TiO2 and titanate nanowires (TNWs) in various applications was the motivation behind studying their stability in this work, given that stability greatly influences both the success of the application and the environmental impact. Due to their high abundance in aqueous environments and their rich technological applicability, surfactants are among the most interesting compounds used for tailoring the stability.The aim of this paper is to determine the influence of surfactant molecular structure on TNW stability/aggregation behavior in water and aqueous NaBr solution by dynamic and electrophoretic light scattering. To accomplish this, two structurally different quaternary ammonium surfactants (monomeric DTAB and the corresponding dimeric 12-2-12) at monomer and micellar concentrations were used to investigate TNW stability in water and NaBr. It was shown that TNWs are relatively stable in Milli-Q water. However, the addition of NaBr induces aggregation, especially as the TNW mass concentration increases. DTAB and 12-2-12 adsorb on TNW surfaces as a result of the superposition of favorable electrostatic and hydrophobic interactions. As expected, the interaction of TNWs with 12-2-12 was stronger than with DTAB, due to the presence of two positively charged head groups and two hydrophobic tails. As a consequence of the higher adsorption of 12-2-12, TNWs remained stable in both media, while DTAB showed an opposite behavior.In order to gain more insight into changes in the surface properties after surfactant adsorption on the TNW surface, a surface complexation model was employed. With this first attempt to quantify the contribution of the surfactant structure on the adsorption equilibrium according to the observed differences in the intrinsic log K values, it was shown that 12-2-12 interacts more strongly with TNWs than DTAB. The modelling results enable a better understanding of the interaction between TNWs and surfactants as well as the prediction of the conditions that can promote stabilization or aggregation.

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.

Dalmatian pyrethrum (Tanacetum cinerariifolium /Trevir. /Sch. Bip.) is a plant species of the Asteraceae family, restricted to the eastern coast of the Adriatic Sea. It is a perennial plant species known as the source of natural insecticide pyrethrin. The term pyrethrin refers to the six insecticide active components: pyrethrin I and II, cinerin I and II, jasmolin I and II. Insecticidal potential of Dalmatian pyrethrum is measured by the content and composition of pyrethrins which are mainly concentrated in the flower heads. In order to obtain deeper knowledge of its insecticidal potential, content and composition of pyrethrins was assessed by matrix-solid phase extraction (MSPD). The preliminary experiments were carried out to optimize the main parameters affecting MSPD, such as the type of sorbent and the solvent polarity. Results showed that pyrethrins I and pyrethrins II were successfully extracted by florisil as a sorbent using 10 mL of acetone : ethyl-acetate = 1:1 (v/v) as an elution solvent. All experiments were performed using 1:2 ratio of flower heads and sorbent. Extraction efficiency was determined by high performance liquid chromatography with diode array detector (HPLC- DAD). Separation and quantification of the selected components were carried out under gradient elution of mobile phase (0.1% formic acid in water and 0.1% formic acid in acetonitrile) based on Luna C18(2) column, 250 mm x 4.6 mm, particle size 5 μm (Phenomenex).