Direct observation of frits and dynamic air bubble formation in capillary electrochromatography using confocal fluorescence microscopy

Confocal fluorescence microscopy has been used to study the capillary electrochromatography (CEC) frits and dynamic air bubble formation under real chromatographic conditions. Confocal fluorescence microscopy provides a nondestructive way to view the three-dimensional structure of the frits with high spatial resolution. Frits prepared with four different procedures were studied: (1) sintering bare silica beads with sodium silicate; (2) sintering bare silica beads wetted with water; (3) sintering C18 beads wetted with water; and (4) sintering C18 beads wetted with water and then surfaced-recovered with C18. Frits prepared with sintering silicate-wetted beads have a high degree of heterogeneity, while the other three types of frits have similar, more homogeneous packing structures. Confocal fluorescence microscopy also provides sufficient temporal resolution for in situ observation of the dynamic processes in air bubble formation. In this study, air bubble formation is imaged during the reorganization process of the packing bed and is shown to occur close to the border between the packing bed and the outlet frit. Confocal fluorescence microscopy opens a new avenue in studying dynamic processes in situ in CEC separations.     

Investigations on the distribution of polymer additives in polypropylene using confocal fluorescence microscopy

Within this work, a fluorescence microscopy approach for the investigation of the distribution of polymer additives in polypropylene is presented. The fluorescent whitening agent 2,5-bis-(5-tert-butyl-benzoxazol-2-yl)-thiophene was used as a model compound representing other groups of polymer additives. So far, methods reported in the literature such as UV and IR microscopy offer a high spatial resolution, however, suffer from poor sensitivities, thus not allowing them to analyze samples with low additive concentrations typically used in engineering materials. Using the fluorescence microscopy technique, it was shown that independent from the applied concentrations (0.1–1.7?wt%), additives are distributed on a spherulitic scale with the majority being found at the spherulite boundary and only traces in the center. Furthermore, it could be demonstrated that the additive distribution is affected not only by the spherulite sizes but also by the cooling rate of the polymer melt leading to more or less pronounced additive distribution patterns.     

Visualisation of biopolymer mixtures using confocal scanning laser microscopy (CSLM) and covalent labelling techniques

Confocal scanning laser microscopy (CSLM) has been used to study the behaviour of mixtures of proteins, gelatine, whey proteins and β-lactoglobulin, and polysaccharides, dextran, gellan gum, carrageenan, gum Arabic, and starch. CSLM proved to be a suitable technique to visualise the microstructure of these (phase separated) mixtures in two and three-dimensional images. Contrast through fluorescence is obtained either by covalent labelling (polysaccharides and proteins) or non-covalent labelling (proteins and starch). Double and triple labelling allows the visualisation of individual components in a complex mixture of biopolymers.     

Microstructure of acid-induced caseinate gels containing sucrose: quantification from confocal microscopy and image analysis

We investigate the effect of sucrose on the microstructure of sodium caseinate gels induced by acidification. The average pore size and the fractal properties of two-dimensional slices of the gels are studied using confocal scanning laser microscopy and image analysis. The addition of sucrose promotes stronger and more fine-stranded gels while re-arrangements of the network tend to be prevented. Whereas the fractal dimension itself is not sensitive to changes in the gel microstructure upon addition of sucrose, the maximum cut-off distance, up to which fractal scaling behaviour applies, is substantially reduced, as is the average pore size. The overall microstructural changes seem to be consistent with previous rheological and light scattering studies of the same system.     

A highly sensitive fluorescent probe for tracking intracellular zinc ions and direct imaging of prostatic tissue in mice

A highly sensitive fluorescent sensor ZnDN was designed, synthesized and used for tracking intracellular zinc ions in various living cells and direct imaging of prostatic tissue in mice. ZnDN was prepared from the heterocyclic-fused naphthalimide fluorophore, and the zinc receptor, N,N-bis(2-pyridylmethyl)ethylenediamine (BPEN). Upon addition of Zn²⁺ to the solutions of ZnDN, a remarkable fluorescence enhancement was observed, which could be attributed to the photo-induced electron transfer (PET) mechanism. Since ZnDN exhibited high sensitivity toward Zn²⁺ in phosphate buffer solution, with a limit of detection of 4.0 × 10⁻⁹ mol/L, it was further applied for the imaging of exogenous and endogenous Zn²⁺ in different living cells. Living cells imaging experiments suggested that ZnDN could image the changes of intracellular free zinc ions, and could be used for two-photon imaging. Moreover, flow cytometry suggested that ZnDN could distinguish cancerous prostate cells from normal cells. Animal experiments indicated that ZnDN had the potential in imaging prostate tissue in vivo.     

Determination of the chemical composition and Raman characterization of barite samples from Denizli and Akdamadeni,Turkey, using Energy Dispersive X-ray fluorescence and Raman microscopy

Accurate analysis of samples is very important for scientists working in many fields. XRF device is used very frequently especially in mine analysis. However, researchers are trying to reach accurate results with many different analysis methods. In addition to the known analysis methods, alternative research methods also guide the studies. In this study, two barite ore samples, collected from two regions of different nature (Denizli and Akda?madeni) by following specified sampling methods, were analyzed using Confocal Raman Spectroscopy (CRS) and Polarized Energy Dispersive X-Ray Fluorescence (PEDXRF) spectrometer. The first sample was from a metamorphic basement, and the second was from an alkali syenite rock unit. The main objective of this paper is to compare the optical characteristics of these two different barite samples collected from different regions under a polarized microscope, using CRS and PEDXRF. The results of polarized microscopy analysis showed that the barite taken from Denizli is associated with calcite. On the other hand, the barite taken from Akda?madeni is associated with galena, celestite, and quartz. Two different colors were observed in the barite samples. CRS and PEDXRF results showed that the barites collected from two regions differed in mineral association, chemical composition, and physical properties. The accuracy of the chemical analysis technique was ensured by following USGS standards, GBW 7109, and GBW-7309 Sediment. Barite ores were analyzed using HR-800 (HORIBA-Jobin Yvon) CRS and a polarized microscope (Leica DMLP). Thanks to this study, it has been shown that mineral analyzes can be performed with an accuracy close to XRF with Confocal Raman spectroscopy. Confocal Raman spectroscopy will also guide researchers for mineral analysis.     

A highly sensitive fluorescent probe for tracking intracellular zinc ions and direct imaging of prostatic tissue in mice

A highly sensitive fluorescent sensor ZnDN was designed, synthesized and used for tracking intracellular zinc ions in various living cells and direct imaging of prostatic tissue in mice. ZnDN was prepared from the heterocyclic-fused naphthalimide fluorophore, and the zinc receptor, N,N-bis(2-pyridylmethyl)ethyl-enediamine (BPEN). Upon addition of Zn²⁺ to the solutions of ZnDN, a remarkable fluorescence enhancement was observed, which could be attributed to the photo-induced electron transfer (PET) mechanism. Since ZnDN exhibited high sensitivity toward Zn²⁺ in phosphate buffer solution, with a limit of detection of 4.0×10^-9 mol/L, it was further applied for the imaging of exogenous and endogenous Zn²⁺ in different living cells. Living cells imaging experiments suggested that ZnDN could image the changes of intracellular free zinc ions, and could be used for two-photon imaging. Moreover, flow cytometry suggested that ZnDN could distinguish cancerous prostate cells from normal cells. Animal experiments indicated that ZnDN had the potential in imaging prostate tissue in vivo.     

Identification of lead pigments in nanosamples from ancient paintings and polychromed sculptures using voltammetry of nanoparticles/atomic force microscopy

Voltammetry of nanoparticles coupled with atomic force microscopy was used to identify lead pigments in nanosamples proceeding from works of art. Upon mechanical attachment of few nanograms of sample to a graphite plate, well-defined voltammetric responses were obtained for lead orange, lead yellow, lead white, litharge, minium, Naples yellow, and tin-lead yellow, allowing for an unambiguous identification of such pigments. Atomic force images provide evidence for the occurrence of pigment-characteristic reduction processes accompanied by metal deposition on the graphite substrate. Electrochemical parameters are used for pigment identification. Application to the method for identifying lead pigments in different model binder + pigment specimens and pictorial samples from the canvas painting collection (anonymous, 17th century) of the Saint Joseph Church in Taormina (Italy), the frescoes painted by Antonio Acisclo Palomino y Velasco (1698) in the vault of the Sant Joan del Mercat church in València (Spain) and an anonymous polychromed sculpture (16th century) representing a Martyr Saint from Alacant (Spain) is described.