91. Optimized frequency dependent photothermal beam deflection spectroscopyMladen Franko, Dorota Korte, Humberto Cabrera, 2016, original scientific article Abstract: In the paper the optimization of the experimental setup for photothermal beam deflection spectrometry is performed by analyzing the influence of its geometrical parameters (detector and sample position, probe beam radius and its waist position etc) on the detected signal. Furthermore,
the effects of fluid’s thermo-optical properties, for optimized geometrical configuration, on the
measurement sensitivity and uncertainty determination of sample thermal properties is also studied.
The examined sample is a recently developed CuFeInTe3 material. Results show, that it is a complex problem to choose the proper geometrical configuration as well as
sensing fluid to enhance the sensitivity of the method. A signal enhancement is observed at low modulation frequencies by placing the sample in acetonitrile (ACN), while at high modulation frequencies the sensitivity is higher for measurements made in air. For both, detection in air and
acetonitrile the determination of CuFeInTe3 thermal properties is performed. The determined values of thermal diffusivity and thermal conductivity are (0.048 ± 0.002) × 10−4 m2 s−1 and 4.6 ± 0.2 W m−1 K−1 and (0.056 ± 0.005) × 10−4 m2 s−1 and 4.8 ± 0.4 W m−1 K−1 for ACN and air,
respectively. It is seen, that the determined values agree well within the range of their measurement uncertainties for both cases, although the measurement uncertainty is two times lower for the measurements in ACN providing more accurate results. The analysis is performed by the use of
recently developed theoretical description based on the complex geometrical optics. It is also shown, how the presented work fits into the current status of photothermal beam deflection spectroscopy.
Keywords: Optitermi, na spektrometrija, toplotna difuzivnost, toplotna prevodnost, polprevodniki, vpliv topila
Published in RUNG: 07.11.2016; Views: 6456; Downloads: 0
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92. TLS Spectrometry & Detection in Liquid Chromatography, FIA and Microfluidic SystemsMladen Franko, invited lecture at foreign university Abstract: This presentation provides theoretical backround for thermal lens spectrometry (TLS) and TLS microscopy (TLM) and describes the basic instrumentation for TLS and TLM measurements. Presented applications of TLS and TLM include detection in HPLC (carotenoids, bilirubin, biliverdin), FIA (alergens, Ag, Ag+, phytoplankton and cyanobacterial pigments, organophospate pesticides) and TLM detection in microfluidic systems (Cr(VI), microcystin, NGAL, study of diffusion proceses)
Keywords: Spekrometry TLS, TLM, HPLC, FIA, microfluidics, bilirubin, biliverdin, carotenoids, alergens, mikrocystin, pigments, organophosphate pesticides, NGAL, Ag, Cr(VI), diffusion
Published in RUNG: 16.09.2016; Views: 6804; Downloads: 9
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93. Bilirubin is an Endogenous Antioxidant in Human Vascular Endothelial CellsLovro Žiberna, Mitja Martelanc, Mladen Franko, Sabina Passamonti, 2016, original scientific article Abstract: Bilirubin is a standard serum biomarker of liver function. Inexplicably, it is inversely correlated with
cardiovascular disease risk. Given the role of endothelial dysfunction in originating cardiovascular
diseases, direct analysis of bilirubin in the vascular endothelium would shed light on these relationships.
Hence, we used high-performance liquid chromatography coupled with thermal lens spectrometric
detection and diode array detection for the determination of endogenous cellular IXα-bilirubin. To
confirm the isomer IXα-bilirubin, we used ultra-performance liquid chromatography coupled with a
high-resolution mass spectrometer using an electrospray ionization source, as well as tandem mass
spectrometric detection. We measured bilirubin in both arterial and venous rat endothelium (0.9–1.5
pmol mg−1 protein). In the human endothelial Ea.hy926 cell line, we demonstrated that intracellular
bilirubin (3–5 pmol mg−1 protein) could be modulated by either extracellular bilirubin uptake, or by
up-regulation of heme oxygenase-1, a cellular enzyme related to endogenous bilirubin synthesis.
Moreover, we determined intracellular antioxidant activity by bilirubin, with EC50 = 11.4 ± 0.2 nM, in
the range of reported values of free serum bilirubin (8.5–13.1 nM). Biliverdin showed similar antioxidant
properties as bilirubin. We infer from these observations that intra-endothelial bilirubin oscillates, and
may thus be a dynamic factor of the endothelial function.
Keywords: Antioxidants, bilirubin, endothelial cells
Published in RUNG: 07.07.2016; Views: 6341; Downloads: 409
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94. Determination of biogenic amines by thermal lens microscopic detection of enzymatically released ammoniumMojca Žorž, Mladen Franko, 2016, published scientific conference contribution abstract Abstract: Biogenic amines (BAs) are organic amines present in meat, fish, dairy produce and wine due to the breakdown of amino acids, catalysed by microbial decarboxylases. BAs determination in food is important not only because of possible toxicological effects such as nausea, sweating and headache but also due to their possible role as indicators of food spoilage. Chromatographic methods are traditionally applied for determination of BAs in food [1], which usually require preliminary operations for sample pre-treatment that are laborious and difficult to automate. On the other hand, screening analytical systems provide simple, low cost and rapid analysis with the possibility of subjecting high number of samples to the screening system in a short time [2]. In this work we present a novel method for screening determination of BAs using a microfluidic system with the detection by highly sensitive thermal lens microscope (μFIA-TLM).
Four biogenic amines (putrescine, cadaverine, histamine and tyramine) were subjected to enzymatic catalysis by transglutaminase, where ammonia was released as a product of acyl transfer reaction between the peptide bound glutamine (Gln) and the amino group of BAs. Ammonia was further transformed into indophenol blue by the Berthelot reaction. The coloured product was detected in batch (static) mode in a 100 μm sample cell or in μFIA (flowing) mode in a microchip with the same optical path length. The detection was performed on a TLM system applying a solid-state diode as an excitation source (660 nm). Organic solvents were tested for signal enhancement.
For evaluation of the sensitivity and determination of LOD values (S/N = 3 basis), the NH4Cl standard solution was applied in Berthelot reaction with further detection on TLM system. The LODs for NH4+ in batch mode and in μFIA were 24 μg/L and 109 μg/L, respectively. Both LOD values are lower than the LOD achieved with conventional spectrophotometry (180 μg/L). When mixtures of the indophenol standard solutions and EtOH in the ratio of 1:1 were prepared the LOD in batch mode was improved to 3 μg/L, achieving 60-times improvement compared to spectrophotometry.
Keywords: Biogenic amines, Thermal lens microscopy, microfluidics, translgutaminase
Published in RUNG: 05.07.2016; Views: 6977; Downloads: 0
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95. Highly Sensitive Determination of Pyoverdine in Cloud Water by HPLC-Thermal Lens SpectrometryLeja Goljat, Mitja Martelanc, Virginie Vinatier, Anne-Marie Delort, Mladen Franko, 2016, published scientific conference contribution abstract Abstract: New method for pyoverdine and Fe(III)-pyoverdine detection was developed. Two isomers of pyoverdine and two isomers of Fe(III)-pyoverdine were separated isocraticaly on reversed-phase (RP)-C18 chromatograhic column and detected by DAD, FLD and TLS. HPLC-TLS method enables separation and determination of pyoverdine and Fe(III)-pyoverdine in a single run and excels in superior sensitivities when compared to conventional HPLC-DAD system.
Keywords: Pyoverdine, Fe(III)-pyoverdine, cloud water, high-performance liquid chromatography, thermal lens spectrometry
Published in RUNG: 04.07.2016; Views: 7280; Downloads: 0 |
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