11. 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: 4722; Downloads: 0
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12. Identifikacija, porazdelitev in vezavne oblike železa v rižu (Oryza sativa L.) z rentgensko absorpcijsko in emisijsko mikro-spektroskopijoBojan Šuc, 2016, undergraduate thesis Abstract: V diplomskem delu smo raziskali vezavne oblike železa v različnih delih korenin riža s kombinacijo rentgenske absorpcijske spektroskopije in mikroskopije z metodo mikro-XANES. S tem smo želeli izboljšati razumevanje vnosa železovih spojin v rastline riža (Oryza sativa L.) na tkivnem nivoju. Rastline riža so bile vzgojene v hidroponskem sistemu z dodanim železom Fe2+ (kot FeSO4). Spektri mikro-XANES na absorpcijskem robu K železa so bili pomerjeni na prečnih rezinah korenin, zamrznjenih v tekočem dušiku, na žarkovni liniji ID21 sinhrotrona ESRF v Grenoblu v fluorescenčnem načinu. Pri analizi spektrov mikro-XANES smo preučili uporabnost metode linearnega kombiniranja referenčnih spektrov XANES železa izmerjenih na nizu referenčnih dvo- in trivalentnih železovih spojin. Rezultati so pokazali, da je možno s to metodo v rastlinskih vzorcih jasno ločiti med dvo- in trivalentnimi železovimi kompleksi in določiti njihov delež z natančnostjo ±1%. Prevladujoča valenca železa v vzorcih korenin je Fe3+. Prepoznavanje in razločevanje različnih železovih kompleksov je manj natančno. Natančnost pri določanju deleža različnih trivalentnih železovih kompleksov je med 10% in 30%. Nekaterih železovih kompleksov s to metodo ni mogoče razločiti med sabo, ker se njihovi spektri XANES premalo razlikujejo. Kot najpogostejše železove komplekse v koreninah riža smo prepoznali Fe2+-fitat med dvovalentnimi spojinami, med trivalentnimi pa: železov oksid/hidroxid Goethit α-FeOOH Fe3+-citrat in Fe3+-fitat. Na natančnost pri razločevanju železovih spojin znatno vplivajo statistični šum in sistematske napake v izmerjenih spektrih mikro-XANES. Rezultati razmerij med dvo- in trivalentnimi železovimi kompleksi v različnih delih korenin kažejo, da se rastline riža zaščitijo pred strupenim toksičnim dvovalentnim železom tako, da ga oksidirajo in tvorijo tako imenovani plak, oziroma oborino, s čimer omejijo vnos dvovalentnega železa.
Keywords: Rentgenska absorpcijska spektrometrija, riž, železo, mikro-XANES, metoda linearnega kombiniranja referenčnih spektrov
Published in RUNG: 06.09.2016; Views: 7955; Downloads: 241
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14. Microfluidic flow injection thermal lens microscopy for high throughput and sensitive analysis of sub-μL samplesMingqiang Liu, Sara Malovrh, Mladen Franko, 2016, original scientific article Abstract: An analytical method combining microfluidic flow injection analysis (μFIA) with thermal lens microscopy (TLM) was developed for high throughput and sensitive analysis of sub-μL samples. Performance of the μFIA-TLM was validated for detection of hexavalent chromium [Cr(VI)] in water samples. At different sample injection volumes, detection positions and flow rates, influences of the reaction time and the diffusion of Cr-diphenylcarbazone (DPCO) complexes on the μFIA-TLM signal were investigated. Photodegradation of the Cr-DPCO complex was clearly observed when the absorbed photons per Cr-DPCO is above 1600. After optimization of the TLM with respect to rapid flows (up to 10 cm/s), we achieved a limit of detection of 0.6 ng/mL for Cr(VI) in a 50-μm deep channel. Impacts of interfering ions [V(V), Mo(VI), Fe(III)] on the Cr(VI) determination were found to be small. Cr(VI) in real samples from a cement factory were determined and found in good agreement with results of spectrophotometry. This μFIA-TLM shows advantages over its conventional counterpart, such as eliminating additional sample conditioning, reducing over 100 times the sample consumption to sub-μL and over 10 times the time required for one sample injection to a few seconds (up to 20 samples/min). The optimized μFIA-TLM setup can be applied for fast and sensitive analysis of nonfluoresent sub-μL samples in rapidly flowing mediums.
Keywords: Spektrometrija TLS, mikroskopija TLM, mikrofluidika, krom (VI)
Published in RUNG: 01.06.2016; Views: 5222; Downloads: 270
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15. Oxidation as a pre-step in determination of organophosphorus compounds by the AChe-TLS bioassayMojca Bavcon Kralj, Polonca Trebše, Mladen Franko, 2006, original scientific article Keywords: analizna kemija, analitska kemija, bioanalitske tehnike, organofosfatni pesticidi, oksidacija, učinkovitost kemijske oksidacije, kemijska analiza, plinska kromatografija na masno detekcijo, GC-MS, spektrometrija na osnovi termičnih leč, AChE-TLS, NBS
Published in RUNG: 15.10.2013; Views: 6538; Downloads: 32
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