Martyna Nowak

Concentration and Fractionation of Polyphenols by Membrane Operations

BACKGROUND This review aims to present the relevant background information and current research status in concentration of polyphenols using membrane technologies. The potential implementation of membrane separation to bioactive compounds like soluble phenolics from aqueous and organic solvent solutions is gaining increasing interest in the recent years. This review does not pretend to cover the abundant published literature on the subject, but to be representative for the observed tendencies in membrane processes applications for concentration of polyphenols derived from natural products. The first part of the article includes general information regarding the polyphenols and the traditional methods for their separation (such as: thin layer chromatography; paper chromatography; gas chromatography; high performance liquid chromatography; capillary electrophoresis), while the second part presents a review of different membrane processes applied for concentration of polyphenols. Three main sources for such implementations are discussed: (1) aqueous or organic solvent extracts from plant material, (2) fruits, and (3) recovery of polyphenols from industrial waste liquids. A diversity of membrane processes are considered in a large scope of implementations ranging from lab-scale studies to pilot and semiindustrial scale operations. CONCLUSION Membrane technology is an excellent candidate to make a paradigm shift in biological active compounds fractionation/separation processes. Presented results clearly demonstrate that membrane processes are of great advantages over traditionally used methods; however, characterization of separated polyphenols has to be improved. Most of citied authors concentrated their investigation only on the total amount of polyphenols determination. Exhaustive studies including: antioxidant activities, retention index, total soluble solids, or volume reduction factor, have been only carried out by a few authors.

Complexation copper(II) or magnesium ions with d-glucuronic acid – potentiometric, spectral and theoretical studies

Abstract Results of potentiometric and spectral studies have shown that in d-glucuronic acid (GluA) with Cu2+ or Mg2+ systems, the complexes ML and ML(OH)x are formed. Overall stability constants (log β) and equilibrium constants (log Ke) were calculated for all complex forms. The mode of coordination for each form was concluded on the basis of spectral values, Vis, EPR, and chemical shifts in the 13C NMR. According to spectral analysis, Cu(GluA) exists in two possible forms, which confirm the occurrence of the coordination dichotomy in the system. The main center of interactions in the hydroxyl complexes Cu(GluA)(OH)x and MgGluA are oxygens from the carboxyl group. Differences in the coordination mode in the copper(II) and magnesium systems at low pH were observed.

Preparation of silver material used for detection of biocomplexes by surface-enhanced Raman scattering

Silver dendrites were obtained on Cu plate by a classic galvanic displacement process. The process of preparing Ag particles was performed at different immersion times in AgNO3 solution, and the best process parameters were selected according to the enhancement effect of the Raman spectra of Rhodamine 6G. Ag-Cu substrates were chosen for a Surface-enhanced Raman scattering (SERS) study of biocomplexes because their preparation is cost effective and simple, and the relative homogeneous signal enhancement on the prepared silver SERS-active substrate was obtained. The rapid process of surface preparation was applied to identify the mode of coordination. Biocomplexes of Co and Ni ions with adenosine triphosphate form in neutral pH were immersed on the Ag dendrites, and SERS spectra of these compounds were collected. This research work was carried out in order to determine different types of coordination in the same pH conditions and relatively low concentration using SERS which is an emerging and promising te...

Heteronuclear complexes of phosphocreatine with copper(II) and magnesium(II) ions

It has been found that in the binary systems Mg(II)/phosphocreatine and Cu(II)/phosphocreatine at low pH, metal ions mainly coordinate via the phosphate group. At higher pH for copper(II) system, the efficiency of –PO32− group is low and coordination takes place via amine and carboxyl groups (Mg2+ is still coordinated to phosphate group). Differences in the coordination mode for copper and magnesium ions in binary systems at high pH suggested that it would be interesting to determine the mode of coordination in heteronuclear complexes and the coordination competitiveness of metal ions towards phosphate group at low and at physiological pH. The formation of heteronuclear complexes of phosphocreatine with Mg2+ and Cu2+ ions was investigated. The overall stability constants of these species were determined by the potentiometric studies and the coordination mode was concluded on the basis of several spectral investigations (EPR, Visible Spectroscopy, 2D 1H-15N NMR, 31P NMR and FT-IR).

Carboxyl groups of citric acid in the process of complex formation with bivalent and trivalent metal ions in biological systems

Binary complexes of citric acid (H3L - protonated form, H2L and HL - partly protonated forms, L - fully deprotonated) with d- and f-electron metal ions were investigated. The studies have been performed in aqueous solution using the potentiometric method with computer analysis of the data, electron paramagnetic resonance, infrared, visible as well as luminescence spectroscopies. The overall stability constants of the complexes were determined. Analysis of the equilibrium constants of the reactions and spectroscopic data has allowed determination of the type of coordination and effectiveness of the carboxyl groups in the process of complex formation. On the basis of potentiometric titration for d-electron were found dimeric and monomeric type of complexes and for f-electron four type of complexes: MHL, ML, ML(OH) and ML(OH)2.

Applications of silver nanoparticles stabilized and/or immobilized by polymer matrixes

Abstract Nanomaterials frequently possess unique and noticeably changed physical, chemical and biological properties compared to their macro scaled corresponding item. Utilization of nanoparticles habitually requires the construction of integrated chemical systems. Most popular of these are polymer-supported nanoparticles. In this review, we provide the reader with the last developments and breakthrough technologies concerning silver nanoparticles (AgNPs), one of the most comprehensively studied nanomaterials, considering the polymer types and processes used for the nanocomposite membranes preparation.