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1.
Določevanje kroma(VI) v mikrofluidnem sistemu z optotermično mikroskopsko detekcijo
Sara Malovrh, 2015, undergraduate thesis

Abstract: Krom (Cr) spada med kovinske onesnaževalce, katerega učinek na okolje je močno odvisen od oksidacijskega stanja. Za ljudi je problematična njegova šestvalentna oblika Cr(VI), ki je rakotvorna, zato je potreba po hitri detekciji Cr(VI) velika. V diplomski nalogi smo preverjali točnost detekcije Cr(VI) ob prisotnosti različnih presežkov motečih elementov kot so šestvalentni molibden (Mo(VI)), petvalentni vanadij (V(V)), trivalentno železo (Fe(III)) in dvovalentno živo srebro (Hg(II)). Po kolorimetrični reakciji čistega standarda Cr(VI) in raztopin motečih elementov z difenilkarbazidom (DPC) smo za meritev uporabili spektrofotometrijsko metodo (SPEC) in mikroskopijo s toplotnimi lečami v mikrofluidnem sistemu za pretočno injekcijsko analizo (µFIA - TLM). Rezultati so pokazali, da največjo napako pri meritvah povzroči prisotnost V(V). Izvedli smo tudi študijo razpada preiskovanih kompleksov Cr-DPCO, Mo-DPCO, V-DPCO, Fe-DPCO in Hg-DPCO v odvisnosti od moči vzbujevalnega laserja v mikrofluidnem TLS sistemu (TLM). Dokazali smo, da je železov kompleks stabilnejši od ostalih preiskovanih ionskih kompleksov, ki so znani kot fotolabilni. Z izračunom spodnje meje določevanja (LOD) za SPEC in TLM metodo smo pokazali, da je TLM, zaradi nižje LOD vrednosti primernejša metoda za detekcijo nizkih koncentracij Cr(VI) v vzorcu. Analiza vzorcev iz Soče in Ljubljanice je prikazala sliko realnega stanja v, potencialno s Cr(VI), onesnaženi reki.
Found in: osebi
Keywords: spektrofotometrija, TLS, TLM, fotolabilnost, moteči elementi
Published: 30.09.2015; Views: 2862; Downloads: 160
.pdf Fulltext (1,62 MB)

2.
Microfluidic flow injection thermal lens microscopy for high throughput and sensitive analysis of sub-μL samples
Mladen Franko, Sara Malovrh, Mingqiang Liu, 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.
Found in: osebi
Keywords: Spektrometrija TLS, mikroskopija TLM, mikrofluidika, krom (VI)
Published: 01.06.2016; Views: 1963; Downloads: 130
.pdf Fulltext (828,33 KB)

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