Schiff Bases Derived from Aminopyridines as Spectrofluorimetric Analytical Reagents

Fluorescence characteristics of Schiff bases derived from aminopyridines and salicylaldehyde were studied and possibilities of their analytical application were discussed. It is shown that these compounds can be used for spectrofluorimetric monitoring of small pH changes as well as for sensitive metal ion determinations. As an illustration of metal ion determination, a spectrofluorimetric procedure for analysis of Cu2+ is presented. Determination of Cu2+ was based on the quenching effect of Cu2+ on the fluorescence of N,N\u27-bis(salicylidene)-2,3-pyridinediamine in dioxan/water 1/1 (volume fraction of dioxan, φ = 50%). Under optimal conditions (pH = 8.9, λex = 340 nm, λem = 385 nm, cligand = 1.0 x 10-5 M), the linearity range of the calibration curve was 30-350 μg L-1 Cu2+. The procedure is fast, simple and reproducible. It is characterized by high sensitivity and satisfactory selectivity. An additional advantage of Schiff bases derived from aminopyridines as analytical reagents lies in the simplicity of preparation procedures, enabling improvement of the determination methods not only by optimization of experimental conditions, but also by designing suitable struetural characteristics of the reagent

ESI MS/MS Study of Calix[4]arene Derivatives and their Metal Complexes

The peptidocalixarenes 1-3 bearing tryptophan, phenylglycine and leucil units at the lower rim and their complexes with alkali-metal (Li+, Na+, K+, Rb+, Cs+) and selected lanthanide cations (La3+, Ce3+, EU3+, Yb3+) were analyzed by ESI MS. The influences of the solvent (acetonitrile, methanol, addition of formic acid or sodium acetate) and the calixarene:cation molar ratio on signal intensities were investigated. Comprehensive MS/MS analyses were performed of all singly and doubly charged ions of 1-3 and their complexes, and fragmentation pathways were proposed. An inductive cleavage was observed during dissociation of protonated ions, while the presence of alkali-metal or lanthanide cations caused homolytic cleavage and formation of radical cations. The results of MS analysis were in accordance with those obtained by other techniques (spectrophotometric, potentiometric, and conductometric titrations). The MS/MS experiments could be used as fast and sensitive method for prediction of relative stabilities of calixarene complexes with metal ions

Schiff Bases Derived from Aminopyridines as Spectrofluorimetric Analytical Reagents

Fluorescence characteristics of Schiff bases derived from aminopyridines and salicylaldehyde were studied and possibilities of their analytical application were discussed. It is shown that these compounds can be used for spectrofluorimetric monitoring of small pH changes as well as for sensitive metal ion determinations. As an illustration of metal ion determination, a spectrofluorimetric procedure for analysis of Cu2+ is presented. Determination of Cu2+ was based on the quenching effect of Cu2+ on the fluorescence of N,N\u27-bis(salicylidene)-2,3-pyridinediamine in dioxan/water 1/1 (volume fraction of dioxan, φ = 50%). Under optimal conditions (pH = 8.9, λex = 340 nm, λem = 385 nm, cligand = 1.0 x 10-5 M), the linearity range of the calibration curve was 30-350 μg L-1 Cu2+. The procedure is fast, simple and reproducible. It is characterized by high sensitivity and satisfactory selectivity. An additional advantage of Schiff bases derived from aminopyridines as analytical reagents lies in the simplicity of preparation procedures, enabling improvement of the determination methods not only by optimization of experimental conditions, but also by designing suitable struetural characteristics of the reagent

Kiralna separacija beta-blokatora tekućinskom kromatografijom visoke djelotvornosti i određivanje enantiomera bisoprolola u površinskim vodama

Beta-blockers are chiral compounds with enantiomers that have different bioactivity, which means that while one is active, the other can be inactive or even harmful. Due to their high consumption and incomplete degradation in waste water, they may reach surface waters and affect aquatic organisms. To address this issue we developed a chromatographic method suitable for determining beta-blocker enantiomers in surface waters. It was tested on five beta-blockers (acebutolol, atenolol, bisoprolol, labetalol and metoprolol) and validated on bisoprolol enantiomers. Good enantioseparation of all analysed beta-blockers was achieved on the Chirobiotic V column with the mobile phase composed of methanol/acetic acid/triethylamine (100/0.20/0.15 v/v/v) at a flow rate of 0.5 mL/min and column temperature of 45 °C. Method proved to be linear in the concentration range from 0.075 μg/mL to 5 μg/mL, and showed good recovery. The limits of bisoprolol enantiomer detection were 0.025 μg/mL and 0.026 μg/mL and of quantification 0.075 μg/mL and 0.075 μg/mL. Despite its limitations, it seems to be a promising method for bisoprolol enantiomer analysis in surface water samples. Further research could focus on waste water analysis, where enantiomer concentrations may be high. Furthermore, transferring the method to a more sensitive one such as liquid chromatography coupled with tandem mass spectrometry and using ammonium acetate as the mobile phase additive instead of acetic acid and triethylamine would perhaps yield much lower limits of detection and quantification.Beta-blokatori su kiralni spojevi s enantiomerima različite bioaktivnosti, dakle, dok je jedan enantiomer aktivan, drugi može biti neaktivan ili čak štetan za organizam. Zbog njihove visoke potrošnje i nepotpune razgradnje u pogonima za preradu otpadnih voda, postoji mogućnost da se pojave u prirodnim vodama i negativno utječu na vodene organizme. Stoga je u ovom radu razvijena kromatografska metoda za određivanje enantiomera beta-blokatora u prirodnim vodama. Metoda je testirana na pet beta-blokatora (acebutolol, atenolol, bisoprolol, labetalol i metoprolol) te validirana za enantiomere bisoprolola. Dobra enantioseparacija svih analiziranih beta-blokatora postignuta je na koloni Chirobiotic V sastava mobilne faze metanol/octena kiselina/trietilamin (100:0,2:0,15 v/v/v) pri protoku od 0,5 mL/min i temperaturi od 45 °C. Metodom je postignuta dobra linearnost u području od 0,075 μg/mL do 5 μg/mL s dobrim analitičkim povratom. Granice detekcije pojedinih enantiomera bisoprolola bile su 0,025 μg/mL i 0,026 μg/mL, a granice kvantifikacije 0,075 μg/ mL za oba enantiomera. Unatoč ograničenjima metode, pokazala se kao obećavajuća metoda analize enantiomera bisoprolola u površinskim vodama. Daljnja istraživanja mogla bi se izvoditi na otpadnim vodama, gdje bi koncentracije enantiomera mogle biti više. Također, korištenjem osjetljivije metode, primjerice vezanoga sustava tekućinske kromatografije i tandemne spektrometrije masa, te korištenjem amonijeva acetata kao aditiva mobilnoj fazi umjesto octene kiseline i trietilamina, mogle bi se postići znatno niže granice detekcije i kvantifikacije

HPLC Monitoring of Acid Catalyzed Conversion of 7-Ethyltryptophol to Methyl Ester of Etodolac

Small scale experimental model for the preparation of methyl ester of etodolac, the key intermediate in the synthesis of nonsteroidal drug etodolac, is thoroughly investigated in order to define the key parameters needed for its large scale production. Oxa-Pictet-Spengler reaction of 7-ethyltryptophol and methyl 3-oxopentanoate with inorganic acids as catalysts was monitored over time using HPLC method with UV detection. HPLC method for the simultaneous determination of 7-ethyltryptophol and the product was developed first. The conversion of 7-ethyltryptophol to etodolac precursor was performed using different molar equivalents of acid (1-5 with respect to the β-ketoester) and starting 7-ethyltryptophol of different degrees of purity. Kinetic profiles and optimal reaction times were in each case defined and key parameters selected

Degradation of inkjet ink by greensand and ultrasonic sonification

The study describes the degradation of inkjet ink at low frequency ultrasound (US) and greensand to compare their reactivity. Environmental sonochemistry is a rapidly growing area and an example of the advanced oxidation process (AOP) that deals with the destruction of organic species in aqueous solutions. Greensand is a granular material coated with a thin layer of manganese dioxide (MnO2) which is among the strongest natural oxidants. In our study magenta inkjet water-based printing ink was dissolved in distilled water and the solutions obtained after degradation were analysed in terms of total organic compound (TOC) and absorption curves in the visible spectra. Also used for the process monitoring was high performance liquid chromatography (HPLC). The efficiency of discoloration is significantly affected by the effluent pH. The efficiency of discolouration was higher when the pH of initial solution was 2 with respect to the initial solution pH of 5.5. In all solutions, irrespective of the initial pH value and the processing method the oxidation of polyhydric alcohols occurs. Although the decomposition is significant, surface peaks resulting from HPLC analysis are very small. Decolourization is closely related to the cleavage of the – C=C and -N=N- bonds, and oxidation of polyhydric alcohol to the formation of monosaccharides, carboxylic acids or other low molecular weight compounds with a lesser number of unsaturated double bonds. These compounds have low UV absorbance or they absorb below 200 nm and therefore their detection is impossible. Thus, the obtained total organic compound results indicate a small degree of mineralization. The effectiveness of the low-frequency ultrasound (20 kHz) oxidation is similar to the effectiveness of oxidation by greendsand

Complexation of Oxonium and Ammonium Ions by Lower-rim Calix[4]arene Amino Acid Derivatives

Complexation of oxonium and ammonium cations with two calix4arene amino acid derivatives, namely 5,11,17,23-tetra-tert-butyl-26,28,25,27-tetrakis-(O-methyl-D-α-phenylglycylcarbonylmethoxy)-calix[4]arene (1) and 5,11,17,23-tetra-tert-butyl-26,28,25,27-(O-methyl-L-leucylcarbonylmethoxy)calix[4]¬arene (2), in acetonitrile and methanol was studied by means of spectrophotometric and calorimetric titrations at 25 °C. The classical molecular dynamics simulations of the macrocycles and the corresponding complexes with NH4+ and H3O+ were carried out in order to investigate their possible structures in solution. The examined calix[4]arene derivatives were shown to be rather efficient binders for H3O+ cation and moderately efficient for NH4+ in acetonitrile, whereas the complexation of these cations in methanol could not be observed. The structures of the complexes obtained by means of molecular dynamics simulations suggested the involvement of ether and carbonyl oxygen atoms in the complexation of both NH4+ and H3O+. An inclusion of an acetonitrile molecule into the hydrophobic cavity of the free and complexed ligands was observed as well. The difference in binding affinities of 1 and 2 towards NH4+ and H3O+ ions could be explained by taking into account cation solvation, difference in their size and in the strength of hydrogen bonding between cations and the ligand binding sites. (doi: 10.5562/cca2172

Особенности планктонных сообществ Торейских озер (Забайкальский край) в маловодный год

Lakes Barun-Torey and Zun-Torey are the largest water bodies in Zabaikalsky Krai, and they are characterized by long-term cyclic changes in the water level. Samples of the planktonic community (algae and invertebrates) were collected from the Torey Lakes in June, August, and October in the dry 2016. Collection and processing of the samples was carried out using standard hydrobiological methods. The aim of the study was to investigate the planktonic communities in the Torey Lakes. The lakes were in different hydrological phases: Barun-Torey was in the initial filling phase (with isolated small lakes present on the dried bed), and Zun-Torey was in the shallowing phase. Considerable differences were observed between the compositions and structures of the planktonic communities, which were determined by the mineral content of the water. Diverse littoral plankton developed, consisting of 2-25 taxa of algae (total number of taxa – 46) and 2-15 species of invertebrates (total number of species – 29) in the oligohaline small lakes on the bottom of Lake Barun-Torey. The abundance and biomass of aquatic organisms varied within very wide limits: for phytoplankton – from 0.7 × 103 to 1260.0 × 103 cells / L and from 0.1 to 1271.0 mg / m3, and for zooplankton – from 9.2 × 103 to 19370.0 × 103 individuals / m3 and from 3.8 to 361.7 g / m3. Freshwater and euryhaline species were dominant. In polyhaline Lake Zun-Torey, the phytoplankton consisted of 3-12 taxa of algae (total number of taxa – 18), and the invertebrate fauna included only 3 species. The abundance of phytoplankton varied from 12.4 × 103 to 310.7 × 103 cells / L and a biomass from 1.0 to 14.7 mg / m3, and the abundance of zooplankton varied from 55.1 × 103 to 1656.0 × 103 individuals / m3 and a biomass from 1.1 to 85.5 g / m3. Euryhaline and halophilic species dominatedОзера Барун-Торей и Зун-Торей являются самыми крупными водоемами в Забайкальском крае, для них характерна хорошо выраженная цикличность, проявляющаяся в многолетних изменениях уровня воды. Материалом для работы послужили пробы, собранные на Торейских озерах в июне, августе, октябре в маловодный 2016 г. Сбор и обработка материалов проводилась согласно стандартным гидробиологическим методам. Целью работы стало изучение особенностей развития планктонных биоценозов Торейских озер, одновременно находящихся в разных гидрологических фазах: Барун-Торей – в начальной фазе наполнения, Зун-Торей – в фазе снижения уровня воды. В районе северной оконечности высохшего Барун-Торея в пределах дна его ложа отмечались мелкие водоемы, источником питания которых служила многолетняя мерзлота и разгрузка подземных вод по разлому, проходящему по западному берегу озера. В Зун-Торее продолжался процесс обмеления водоема, который закончился практически полным его высыханием осенью 2017 г. Состав и структура фитопланктона и зоопланктона в разные гидрологические периоды имели существенные различия, определяемые уровнем минерализации озерных вод. В олигогалинных водоемах котловины Барун-Торея развивался литоральный планктоценоз, состоящий из 46 таксонов водорослей (при колебаниях от 2 до 25) и 29 видов беспозвоночных (при колебаниях от 2 до 15). Значения численности и биомассы гидробионтов колебались в очень широких пределах: фитопланктон – от 0,7 до 1260,0 тыс. кл/л и от 0,1 до 1271,0 мг/м3, зоопланктон – от 9,2 до 19370,0 тыс. экз/м3 и от 3,8 до 361,7 г/м3. Доминировали пресноводные и эвригалинные виды. Альгофлора полигалинного оз. Зун-Торей состояла из 18 таксонов (при варьировании от 3 до 12), фауна беспозвоночных – из 3 видов. Количественные показатели варьировали от 12,4 до 310,7 тыс. кл/л и от 1,0 до 14,7 мг/м3 для фитопланктона, и от 55,1 до 1656,0 тыс. экз/м3 и от 1,1 до 85,5 г/м3 – для зоопланктона. Преобладали эвригалинные и галофильные вид

Synthesis, Structural Characterization and Hydrogen Bonding of Mono(salicylidene)carbohydrazide

The condensation reaction between carbohydrazide and salicylaldehyde in different solvents gave mono(salicylidene)carbohydrazide (1). The structure of 1 in solution has been determined by using experimental (NMR and UV spectroscopies and Mass spectrometry) and quantum chemical (DFT) me-thods. It has been demonstrated that 1 adopts the hydroxy-one tautomeric form which is in accordance with previously published results for the related systems. Changes in NMR chemical shifts and calculations have pointed towards a formation of intra- and intermolecular hydrogen bonds, the later being weaker and easily broken at higher temperatures. These results can further be exploited for better understanding of the role hydrogen bonds can play in bioactivity of related derivatives. (doi: 10.5562/cca2123

Maceration of Extra Virgin Olive Oil with Common Aromatic Plants Using Ultrasound-Assisted Extraction: An UV-Vis Spectroscopic Investigation

Rosemary (Rosmarinus officinalis), garden sage (Salvia officinalis), summer savory (Satureja hortensis), laurel (Laurus nobilis), and other aromatic plants were put in olive oil and exposed to ultrasounds for different duration. Filtrated oils were dissolved in cyclohexane, and UV-Vis measurements were carried out. Absorbance values corresponding to chlorophylls, carotenoids, flavonoids (370 nm), and polyphenols (around 300 nm) were measured. In addition, for some samples, total phenols were determined using Folin-Denis reagent and compared with the similar maceration procedure in water solvent (instead of olive oil). Maceration without ultrasound in olive oil for each plant was also compared with ultrasound-assisted extraction. The results show that significant amount of aromatic content can be extracted in olive oil by applying ultrasounds for only few minutes, especially for Salvia officinalis powder. The use of UV-Vis measurements is simple but enough to examine the extent of phenol content extraction through such maceration procedure