Volume 70, Issue 8

South Africa is a mineral-rich country and one area in which minerals can be very important is catalysis. Over an extended period of time, homogeneous catalysis has grown to become very useful, particularly in the chemical and pharmaceutical industries. The organometallic compounds required in the catalysis industry have advanced from metallocenes to an alternative in the form of α -diimines. Most α -diimines are prepared from iminopyridyl moieties and are most active with nickel and palladium transition metals. This review providesa history of homogeneous catalysis and a discussion on iminopyridines, with the main focus on the nickel and palladium complexes formed from them. There follows a discussion of the bimetallic nickel and palladium complexes in various catalytic applications such as Suzuki and Heck coupling, with the main focus on ethylene polymerisation. The limitations are addressed and possible solutions presented to overcome those challenges. Several reviews in the related topics are to be found in the literature but not the α -diimine with iminopyridines and bimetallic nickel and palladium metals.

The capillary zone electrophoresis method was developed for the chiral separation of R, S -cinacalcet. Cyclodextrins with different substituents were tested in both acidic and alkaline background electrolytes. The non-ionic cyclodextrin, 2-hydroxypropyl -γ -cyclodextrin, was selected as the best chiral selector. The separation was performed using a positive voltage in a phosphate buffer at pH 2.5. The analytes studied were separated within 12 min. The proposed method was applied to the analysis of tablets containing R -cinalcalcet as the active substance. The enantiopurity of R -cinacalcet in the tablets studied was confirmed. Subsequently, the analysis of tablets spiked with S -cinacalcet (chiral impurity) was also performed. The method here presented makes possible the determination of 0.1 % of S -cinacalcet in tablets. The analytical characteristics of the method, such as linearity, recovery and RSD values of the peak area and the migration time, were evaluated. The inter-day RSD values of the peak area and the migration time were lower than 3.71 % and 1.3 %, respectively.

A method for using a hyperbranched polymer (HBP) as a bridge to link multiple secondary antibodies at HBP branches to amplify the detection response signal on a quartz crystal microbalance (QCM)-based sandwich-type immunosensor is reported. Carboxyl groups were prepared at multiple branches of HBP to make possible chemical binding between HBP and secondary antibodies via the carboxyl–amine reaction. The total mass ovcry antibodies were used to enhance the signal on a QCM chip in comparison with a simple sandwich-type immune reaction. By contrast, the proposed method could cause one antigen to analogously react with multiple secondary antibodies as a result of the branch structure of HBP. The strategy of using HBP as a bridge to link multiple secondary antibodies succeeded in quantitatively detecting the hepatitis B surface antigen (HBsAg). By employing demonstrated HBP bridge-linking, the frequency shift on a QCM chip was approximately 5 times greater than conventional methods without modification at secondary antibodies. The limit of detection of HBsAg was achieved as 2.0 ng mL − 1 , lower than most of the values recorded in the literature measured by the QCM technique. Taking into account the general chemical interaction of immunoreaction, this method has the potential to amplify the signal in sensing many other analytes of interest.

The ability of Trichoderma atroviride F-534 to utilize plant waste byproducts derived from processing of vegetables and fruits, as the major source of organic carbon and nitrogen for growth and protease production, was tested. The submerged cultivation of T. atroviride F-534 in the mineral base of the Czapek–Dox medium supplemented with plant waste byproducts resulted into copious biomass formation and was accompanied by secretion of several proteolytic enzymes. Zymography analysis of fungal culture filtrates showed that the high-molecular weight (HMW)protease(s)(from 100 k Da to 230 kDa) represent the major portion of secreted enzymes. Serine-type proteases and metalloproteases were predominant, although all known types of proteolytic enzymes were detected dependent on the type of inducer (substrate). The most conspicuous feature of secreted proteases was that the zymography patterns were unique for each plant material tested. These results confirm our previous finding obtained with purified proteins. Results also suggest that HMW protease(s) may participatein the heterotrophic/saprophytic/mode of life of this fungus. Their identity remains, however, obscure.

The paper deals with the application of two perspective and promising bioremediation approaches, bioaugmentation and biostimulation, applied to sediment contaminated with polychlorinated biphenyls (PCBs) with the aim to enhance biodegradation of PCBs. Sediments were sampled from Strážsky canal, an industrial waste canal that flows from a former PCB-factory through the Laborec river into the Zemplínska šírava water reservoir, all located in the eastern part of Slovakia. Bioaugmentation of sediments was performed in microcosms using two bacterial isolates with PCB-degradation ability obtained from the contaminated sediment: Achromobacter xylosoxidans , Stenotrophomonas maltophilia . Biostimulation was performed using an addition of cut plants containing terpenes, known as PCB-inducers(ivy leaves and pine needles).Ecotoxicity of the contaminated sediments was evaluated pre-and post-treatment using biotests of the standard aquatic plant Lemna minor , standard contact test using Lactuca sativa var. capitata , and the bioluminescent bacteria Vibrio fischeri . Biostimulation treatment using ivy leaves revealed higher degradation of detectedPCB congeners than that achieved by the addition of pine needles, but moderately higher post-treatment toxicity of the sediment to the bioindicator Lemna minor .

The zero-valent iron (ZVI)/H 2 O 2 Fenton system can be considered as an effective solution for the removal of many of the organic pollutants present in the waste waters generated by the drug manufacturing industry. The hydrogen peroxide concentration and dosage rate were studied in order to improve the efficiency of the oxidant in the TOC reduction and, thereby enhance the overall catalytic performance of the ZVI/H 2 O 2 Fenton system. TOC reductions of up to 80 % and BOD 5 /COD ratios of up to 0.6 were achieved in the waste water as received without dilution (TOC 0 approximately 5gL −1 ) using hydrogen peroxide dose-staggering. This showed that the ZVI/H 2 O 2 process led not only to a decrease in TOC removal but also to an increase in the biodegradability of the by-products formed. The hydrogen peroxide was consumed more efficiently and very low concentrations of iron dissolved (7 mg L −1 ) were obtained in the final effluents. The final values of COD, BOD 5 , the suspended solids’ content and the conductivity of the treated waste water met the limits of the Spanish legal industrial discharge, Decree 57/2005 (Ministry of Environment, Local Government and Planning, Community of Madrid, 2005). In addition, the composite thus formed, consisting of zero-valent iron and iron oxide-oxyhydroxides, can be readily removed from the treated effluent, avoiding any post-treatment step.

The present study reports simultaneous mineralisation and biodetoxification of Ponceau S (3-hydroxy-4-(2-sulfo-4-[4-sulfophenylazo]phenylazo)-2,7-naphthalenedisulfonic acid sodium salt), an azo dye, by UV light assisted oxidation with hydroxyl and sulfate radicals. Metal ion catalysts used in the work were: Fe 2+ and Ag + , and the oxidants used were: hydrogen peroxide and S2O82-${{\text{S}}_{\text{2}}}{\text{O}}_{\text{8}}^{{\text{2 - }}}$. Strategies adopted to make the processes environmentally benign and economically viable by achieving maximum mineralisation in the shortest possible time are described. Mineralisation efficiency (Em) of various systems was found to follow the order: E m (Fe 2+ /H 2 O 2 /UV) > Em(Fe2+/S2O82−/UV)>Em(Ag+/H2O2/UV)≈Em(Ag+/S2O82−/UV).${E_{\text{m}}}\left( {{\text{F}}{{\text{e}}^{2 + }}/{{\text{S}}_2}{\text{O}}_8^{2 - }/{\text{UV}}} \right) > {E_{\text{m}}}\left( {{\text{A}}{{\text{g}}^ + }/{{\text{H}}_2}{{\text{O}}_2}/{\text{UV}}} \right) \approx {E_{\text{m}}}\left( {{\text{A}}{{\text{g}}^ + }/{{\text{S}}_2}{\text{O}}_8^{2 - }/{\text{UV}}} \right).$ Thus, Fe 2+ and HP are the most suitable metal ion catalyst and oxidant respectively, showing higher efficiency at pH 3 followed by that at pH 6.6. It is possible to enhance the Fe 2+ /H 2 O 2 /UV process electrical energy efficiency by maintaining the concentration of Fe 2+ at either 0.05 mM or 0.03 mM and that of the oxidant at 2.5 mM. The bioassay study revealed that the Fe 2+ /S2O82-${{\text{S}}_{\text{2}}}{\text{O}}_{\text{8}}^{{\text{2 - }}}$ /UV process biodetoxification efficiency is higher at pH 3 (93.7 %) followed by that at pH 6.6 (80.1 %) at the concentration of Fe 2+ and S2O82-${{\text{S}}_{\text{2}}}{\text{O}}_{\text{8}}^{{\text{2 - }}}$ of 0.03 mM and 2.5 mM, respectively. Thus, not only the concentration of Fe 2+ , but also the nature of the oxidant and pH play an important role in the biodetoxification process and S2O82-${{\text{S}}_{\text{2}}}{\text{O}}_{\text{8}}^{{\text{2 - }}}$ possesses higher biodetoxification efficiency than H 2 O 2 .

Recent investigations into plant tissues have indicated that the free form of the natural polyphenolic antioxidant, ellagic acid (EA), is much more plentiful than first envisaged; consequently a re-assessment of solvent systems for the extraction of this water-insoluble form is needed. As EA solubility and its UV-Vis spectrum, commonly used for detection and quantification, are both governed by pH, an understanding of this dependence is vital if accurate EA measurements are to be achieved. After evaluating the pH effects on the solubility and UV-Vis spectra of commercial EA, an extraction protocol was devised that promoted similar pH conditions for both standard solutions and plant tissue extracts. The extraction so devised followed by HPLC with photodiode-array detection (DAD) provided a simple, sensitive and validated methodology that determined free EA in a variety of plant extracts. The use of 100 % methanol or a triethanolamine-based mixture as the standard dissolving solvents were the best choices, while these higher pH-generating solvents were more efficient in extracting EA from the plants tested with the final choice allied to the plants’ natural acidity. Two of the native Australian plants anise myrtle ( Syzygium anisatum ) and Kakadu plum ( Terminalia ferdinandiana ) exhibited high concentrations of free EA. Furthermore, the dual approach to measuring EA UV-Vis spectra made possible an assessment of the effect of acidified eluent on EA spectra when the DAD was employed.

High performance liquid chromatography is the most common technique for analysing isoflavones in soy; however, the appropriate sample pre-treatment is required, including extraction and, often, hydrolysis. In the present work, the kinetics of extraction was investigated with regard to the number of extraction steps and their duration for the exhaustive extraction of bonded forms of isoflavones and aglycones. In addition, a systematic experimental study of hydrolysis depending on the temperature and acidity of the medium was conducted. The results showed that the assisted methods were more effective for the isolation of isoflavones. Moreover, the differences between the results obtained using ultrasound-assisted extraction (UAE), microwave-assisted extraction and pressurised liquid extraction were not statistically significant; however, the appropriate number of extraction steps and their duration for UAE were required. The investigation also revealed that, due to the varying susceptibility of glycosides on conversion to free forms and the stability of the aglycones obtained, two parallel hydrolysis procedures should be conducted to obtain the highest hydrolysis efficiency. The optimised conditions, taking into account the shortest time combined with the highest efficiency, were as follows: 4 M HCl and 60 min for genistein; 8 M HCl and 30 min for glycitein and daidzein.

The thermal and thermo-oxidative processes in Aroniamelanocarpa (black chokeberry) were investigated using combined thermo-analytical (TG-DTA) and spectroscopic (FTIR) experimental techniques. Isoconversional analysis revealed that the process in an inert (argon) atmosphere was probably governed by chlorogenic acid degradation, where autocatalysis (described by the empirical Šesták–Berggren model) might occur due to water already present in the early stages of the process through hydrolysis. Thermal degradation is described by the intrinsic kinetic parameters, where the degradation rate increases proportionally with an increase in the heating rate. Under oxidative conditions, the process was found to be primarily driven by neochlorogenic acid degradation. The thermo-oxidative degradation of Aroniamelanocarpa fresh samples can be described by two competitive reactions, where it was established that a cyanidin-3-glucosylrutinoside degradation made a significant contribution to a comprehensive kinetics. This study showed the targeting of the neochlorogenic acid in Aroniamelanocarpa fresh samples to have a strong hydrogen-donating activity, thereby rendering it capable of very efficiently entrapping the peroxy radicals. Current research has demonstrated that the relative contribution of the two competitive reactions to the overall process is highly dependent on the heating rate of the system under consideration.

The flow in a downward divergent channel turns out to be an interesting experimental setup for the observation of upward floating bubbles that appear to be levitating in view of the observer. A more detailed analysis of this flow and its characteristic parameters is necessary for better understanding of this phenomenon. The boundary layer theory was used to derive the velocity field for the experimental setup. The actual flow of a liquid in the presence of a bubble was studied experimentally by measuring the position of the bubble; the data were then statistically processed by an image analysis. Observation of the bubble positions distribution showed that it is reasonable to assume a flat velocity profile of the liquid in the channel and that the bubbles do not tend to move into the boundary layer. In our experiments, volume of the air bubbles floating in water was 200 mm 3 and of that of bubbles floating in aqueous glycerin was 300 mm 3 . Thus, the experiment used in this work is suitable for reliable determination of instantaneous and average bubble rising velocities as well as of those of horizontal and vertical oscillations.

Dodecanoyl isothiocyanate ( I ) reacts additively with anthranilic acid to afford derivatives of thiourea II and benzothiazine III in a one-pot reaction. The cyclisation of thiourea II was achieved using acetic anhydride to form quinazoline derivative IV . The heating of quinazoline IV in acetic anhydride or butan-1-ol gave quinazoline derivatives V or VI , respectively. Benzothiazine III underwent trans-acylation to benzothiazine VII in boiling acetic anhydride. The treatment of IV with hydrazine hydrate, anthranilic acid or ethyl carbazate afforded derivatives of triazoloquinazoline VIII , quinazolinoquinazoline XI or thiosemicarbazide X , respectively. The reaction of I with 2aminophenol or 2-aminothiophenol afforded thiourea derivative XIII or benzothiazole derivative XIV , respectively. Most of the synthesised compounds bear a lauroyl (dodecanoyl) group (a hydrocarbon moiety). The structures of the synthesised compounds were confirmed by microanalytical and spectral data.

A one-pot three-component Biginelli-like reaction of enaminones, aldehydes with urea/thiourea in the presence of 2-pyrrolidonium bisulphate as an acidic ionic liquid catalyst for the preparation of 6-unsubstituted dihydropyrimidinones is described. The excellent yield, short reaction time, simple procedure and avoidance of the use of organic solvents are some advantages of this method.