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1.
PHOTOLYSIS AND ECOTOXICITY OF THE ANTIBIOTIC CIPROFLOXACIN
Ketevan Neparidze, 2017, undergraduate thesis

Abstract: Over the last few decades, numerous pharmaceuticals coming from domestic sewage, livestock, hospitals and industries have been determined in ground, surface and drinking waters. A common example of these pollutants are fluoroquinolones, which are powerful antibiotics used in human and veterinary medicine. The presence of fluoroquinolones in the environment even at low concentration constitutes a threat to ecosystems and human health because they can lead to bacterial resistance issues. Up to now the environmental impacts of fluoroquinolones and their degradation products are not fully understood but it is known that they can negatively affect plants and aquatic organisms. In this study the degradation of ciprofloxacin (CIP) present in synthetic freshwater was investigated under simulated sunlight. Concentrations before and after degradation were determined using HPLC-DAD. The mineralisation rate of the treated solution was monitored on a total organic carbon analyser. The ecotoxicity of the initial samples and the degradation mixtures was assessed on organisms belonging to different trophic levels: a marine bacterium (Vibrio fischeri), a freshwater invertebrate (Daphnia magna) and seed clover (Trifolium repens). In parallel, the EC50 of CIP was determined for all organisms. The Vibrio fischeri and Trifolium repens tests showed that EC50 value was more than 250 mg/L and for Daphnia magna was 190 mg/L. Photolysis of CIP showed that after 90 min of irradiation, CIP was almost totally degraded (99%). Photolysis process of CIP led to the formation of toxic by-products towards Vibrio fischeri. The toxicity test results on Trifolium repens did not show significant difference between the control and the treated plants. Thus, CIP and its degradation products have no effect on the germination or root length of Trifolium repens. Tests on Daphnia magna after 240 min irradiation showed a 94% reduction of the toxic effect. Non-purgeable organic carbon (NPOC) analysis showed that there is no significant mineralisation of the sample even after 240 min of irradiation.
Found in: ključnih besedah
Keywords: Key words: fluoroquinolones, ciprofloxacin, photolysis, toxicity tests, EC50 determination
Published: 31.01.2017; Views: 2298; Downloads: 160
.pdf Fulltext (947,78 KB)

2.
3.
Trace Detection and Photothermal Spectral Characterization by a Tuneable Thermal Lens Spectrometer with White-Light Excitation
Mladen Franko, Dorota Korte, Humberto Cabrera, 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.
Found in: ključnih besedah
Summary of found: ...simpli- es substantially the experimental setup. Determination of Fe(II) concentrations at parts per billion...
Keywords: thermal lens spectrometry, Fe(II) determination, photothermal technique, multi-wavelength excitation
Published: 21.02.2018; Views: 920; Downloads: 0
.pdf Fulltext (889,82 KB)

4.
Novel methods and applications of photothermal techniques for speciation studies in environmental samples
Leja Goljat, Hanna Budasheva, Virginie Vinatier, Anne-Marie Delort, Dorota Korte Kobylinska, Mladen Franko, 2019, published scientific conference contribution abstract

Found in: ključnih besedah
Keywords: photothermal techniques, Fe determination
Published: 16.07.2019; Views: 263; Downloads: 0
.pdf Fulltext (29,62 MB)

5.
A multi-thermal-lens approach to evaluation of multi-pass probe beam configuration in thermal lens spectrometry
Humberto Cabrera, Leja Goljat, Dorota Korte, Ernesto Marin, Mladen Franko, original scientific article

Abstract: In this work, a recently proposed thermal lens instrument based on multi-pass probe beam concept is investigated and described as a multi-thermal-lens equivalent system. A simulation of the photothermal lens signal formation in a multi-thermal-lens equivalent configuration of the system is performed and validated by comparing the experimental signals of single, dual and ten-pass configurations to theoretically calculated values. The theoretically predicted enhancement of the signal is 9 to 10-fold for a weak thermal lens when comparing the ten-pass configuration with the conventional single-pass thermal lens system. Experimentally achieved signal enhancement in the ten-pass system is 8.3 for pure ethanol sample and between 8 and 9 for solutions with different concentrations of the Fe(II) - 1,10-Phenanthroline complex. Additionally, a value of 9.1 was calculated as the ratio of the slopes of the calibration lines obtained using the ten-pass and single-pass configurations. The achieved limit of detection for determination of Fe(II), in the ten-pass configuration, was 0.4 µgL-1, with a relative standard deviation around 4.5%, which compares favorably with previously reported results for TLS determination of Fe(II) in thin samples using low excitation power. For the multi-pass configuration the linear range of measurement is reduced when compared to the single-pass configuration. This is explained by the theoretical analysis of the photothermal signal under multi-pass condition, which shows the important contribution of the nonlinear term in the theoretical expression for the photothermal signal. The ten-pass configuration, which is presented and validated experimentally for the first time, offers important signal enhancement needed in recently developed TLS instruments with tunable, low power excitation sources.
Found in: ključnih besedah
Summary of found: ...configurations. The achieved limit of detection for determination of Fe(II), in the ten-pass configuration, was...
Keywords: Thermal lens spectrometry, Photothermal detection, Trace determination, Chemical sensor
Published: 10.12.2019; Views: 138; Downloads: 0
.pdf Fulltext (656,75 KB)

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