71. Trace Detection and Photothermal Spectral Characterization by a Tuneable Thermal Lens Spectrometer with White-Light ExcitationHumberto Cabrera, Dorota Korte, Mladen Franko, 2018, original scientific article Abstract: In the thermal lens experimental set-up we replaced the commonly employed pump laser by a halogen lamp, combined with an interference lter, providing a tuneable, nearly monochromatic pump source over the range of wavelengths 430–710 nm. Counter-propagating pump and probe beams are used and a 1 mm path-length sam- ple cell together with the interference lter makes an optical cavity, providing ampli cation of the thermal lens signal, which leads to enhancement of the measurement sensitivity, and enables detection of absorbances on the order of 5×10− 6. Ampli ed thermal lens signal allows us to replace the typical lock-in ampli er and digital os- cilloscope with a silicon photodetector, Arduino board, and a personal computer, offering the possibility for a compact, robust and portable device, useful for in- eld absorption measurements in low concentration or weakly absorbing species. The use of a white light source for optical pumping, an interference lter for wavelength selection and direct diagnostic of the thermal lens signal increase the versatility of the instrument and simpli- es substantially the experimental setup. Determination of Fe(II) concentrations at parts per billion levels was performed by the described white-light thermal lens spectrophotometer and the absorption spectrum for 50μg/ L Fe(II)-1,10-phenanthroline was well reproduced with an average measurement precision of 4%. The obtained limits of detection and quantitation of Fe(II) determination at 510nm are 3μgL− 1 and 11μgL− 1, respectively. The calibration curve was linear in the concentration range of LOQ-500μgL− 1 with reproducibility between 2% and 6%, con rming that this instrument provides good spectrometric capabilities such as high sensitivity, tune- ability and good reproducibility. In addition, the versatility of the instrument was demonstrated by recording the photothermal spectrum of gold nanostructured material and determination of excitation wavelength with most ef cient optical to thermal energy conversion, which differs considerably (cca 100 nm) from the absorption maximum of the investigated sample.
Keywords: thermal lens spectrometry, Fe(II) determination, photothermal technique, multi-wavelength excitation
Published in RUNG: 21.02.2018; Views: 6336; Downloads: 0
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72. Univerza v Novi Gorici, Spremljanje, ugotavljanje in zagotavljanje kakovosti, Poročilo za študijsko leto 2013/2014Iztok Arčon, Martina Bergant Marušič, Aleš Bogovič, Lorena Butinar, Gvido Bratina, IMRE CIKAJLO, Saša Dobričić, Elsa Fabbretti, Mladen Franko, Renata Kop, Urška Lavrenčič Štangar, Martin Knez, Katja Mihurko, Jana Laganis, Branka Mozetič Vodopivec, Egon Pavlica, Ingrid Petrič, Samo Stanič, Tea Stibilj Nemec, Arthur Stepanov, Boštjan Potokar, Veronika Piccinini, Peter Purg, Aljaž Rener, Nives Štefančič, Ana Toroš, Tanja Urbančič, Vanesa Valentinčič, Aleš Vaupotič, Sabina Zelinšček, 2014, treatise, preliminary study, study Keywords: zagotavljanje kakovosti, visoko šolstvo, univerza
Published in RUNG: 05.02.2018; Views: 5622; Downloads: 0
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73. NOVEL APPROACHES FOR THE DETERMINATION OF BIOGENIC AMINES IN FOOD SAMPLESMladen Franko, Mojca Žorž, Mitja Martelanc, Sara Budal, 2017, original scientific article Abstract: In this work, new analytical approaches for determination of biogenic amines in wines were developed.
For the first time, we studied the derivatization of BAs in wines with naphthalene- 2,3-dicarboxaldehyde (NDA) and with dabsyl chloride (DBS) and analysis of derivatized BAs by HPLC coupled to fluorescence (HPLC-NDA-FL) and thermal lens spectrometry (HPLC-DBS-TLS) detectors. The sensitivity of the two methods (LODs HPLC-NDA-FL in the range 27-73 μg/L; LODs HPLC-DBS-TLS in the range 3.4-11 μg/L) was higher than that of the official method for biogenic amines in wines, OIV-MA-AS315-18 (60-77 μg/L). For its best performances, the HPLC-DBS-TLS technique was applied to the analysis of putrescine, cadaverine, histamine and tyramine in two white wine samples. Additionally, exploiting the Berthelot reaction, the TLS fast screening of biogenic amines in wines, following the release of ammonia by transglutaminase, was also proposed. This approach allowed us to determine total biogenic amount content in concentrations below 0.1 mg/L, expressed as equivalents of histamine.
Keywords: biogenic amines, NDA, liquid chromatography, TLS, fluorescence, wine
Published in RUNG: 02.11.2017; Views: 5925; Downloads: 278
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74. Facile synthesis, structure, biocompatibility and antimicrobial property of gold nanoparticle composites from cellulose and keratinChieu D. Tran, Franja Prosenc, Mladen Franko, 2018, original scientific article Abstract: A novel, one-pot method was developed to synthesize gold nanoparticle composite from cellulose (CEL), wool keratin (KER) and chloroauric acid. Two ionic liquids, butylmethylimmidazolium chloride and ethylmethylimmidazolium bis(trifluoromethylsulfonyl)imide were used to dissolve CEL, KER and HAuCl4. X-ray diffraction and X-ray photoelectron results show that Au3+ was completely reduced to Au0NPs with size of (5.5 ± 1) nm directly in the composite with NaBH4. Spectroscopy and imaging results indicate that CEL and KER remained chemically intact and were homogeneously distributed in the com- posites with Au0NPs. Encapsulating Au0NPs into [CEL+KER] composite made the composite fully biocom- patible and their bactericidal capabilities were increased by the antibacterial activity of Au0NPs. Specifically, the [CEL+KER+Au0NPs] composite exhibited up to 97% and 98% reduction in growth of antibi- otic resistant bacteria such as vancomycin resistant Enterococcus faecalis and methicillin resistant Staphylococcus aureus, and was not cytotoxic to human fibroblasts. While [CEL+KER] composite is known to possess some antibacterial activity, the enhanced antibacterial observed here was due solely to added Au0NPs. These results together with our previous finding that [CEL+KER] composites can be used for con- trolled delivery of drugs clearly indicate that the [CEL+KER+Au0NPs] composites possess all required properties for successful use as dressing to treat chronic ulcerous infected wounds.
Keywords: Ionic liquid
Green
Sustainable
Polysaccharide
Keratin
Wound dressing
Gold nanoparticles Antibiotic-resistant bacteria
Published in RUNG: 27.09.2017; Views: 5813; Downloads: 0
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