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51.
Trace Detection and Photothermal Spectral Characterization by a Tuneable Thermal Lens Spectrometer with White-Light Excitation
Humberto 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: 4031; Downloads: 0
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52.
53.
DETERMINATION OF Fe2+ IN LIQUID SAMPLES BY THE USE OF AMPLIEFIED THERMAL LENS SPECTROMETRY
Humberto Cabrera, Dorota Korte, Leja Goljat, Mladen Franko, 2017, published scientific conference contribution abstract

Keywords: AMPLIEFIED THERMAL LENS SPECTROMETRY, Fe2+
Published in RUNG: 30.08.2017; Views: 4288; Downloads: 0
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54.
Comparison of Colorimetric Reagents and Their Applicability in Thermal Lens Spectrometry
Leja Goljat, Mikhail A. Proskurnin, Mladen Franko, 2017, published scientific conference contribution abstract

Keywords: thermal lens spectrometry, colorimetric reagents, mercury
Published in RUNG: 30.08.2017; Views: 4275; Downloads: 0
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55.
Development and Validation of a High- Performance Liquid Chromatography– Tandem Mass Spectrometry Method for the Simultaneous Determination of Irinotecan and Its Main Metabolites in Human Plasma and Its Application in a Clinical Pharmacokinetic Study
Bianca Posocco, Elisa Mazzega, Elena Marangon, Giuseppe Toffoli, 2015, original scientific article

Abstract: Irinotecan is currently used in several cancer regimens mainly in colorectal cancer (CRC). This drug has a narrow therapeutic range and treatment can lead to side effects, mainly neutropenia and diarrhea, frequently requiring discontinuing or lowering the drug dose. A wide inter-individual variability in irinotecan pharmacokinetic parameters and pharmacodynamics has been reported and associated to patients’ genetic background. In particular, a polymorphism in the UGT1A1 gene (UGT1A1*28) has been linked to an impaired detoxification of SN-38 (irinotecan active metabolite) to SN-38 glucuronide (SN-38G) leading to increased toxicities. Therefore, therapeutic drug monitoring of irinotecan, SN-38 and SN-38G is recommended to personalize therapy. In order to quantify simultaneously irinotecan and its main metabolites in patients’ plasma, we developed and validated a new, sensitive and specific HPLC–MS/MS method applicable to all irinotecan dosages used in clinic. This method required a small plasma volume, addition of camptothecin as internal standard and simple protein precipitation. Chromatographic separation was done on a Gemini C18 column (3 μM, 100 mm x 2.0 mm) using 0.1% acetic acid/bidistilled water and 0.1% acetic acid/acetonitrile as mobile phases. The mass spectrometer worked with electrospray ionization in positive ion mode and selected reaction monitoring. The standard curves were linear (R20.9962) over the concentration ranges (10–10000 ng/mL for irinotecan, 1–500 ng/mL for SN-38 and SN-38G and 1–5000 ng/mL for APC) and had good back-calculated accuracy and precision. The intra- and inter-day precision and accuracy, determined on three quality control levels for all the analytes, were always <12.3% and between 89.4% and 113.0%, respectively. Moreover, we evaluated this bioanalytical method by re-analysis of incurred samples as an additional measure of assay reproducibility. This method wassuccessfully applied to a pharmacokinetic study in metastatic CRC patients enrolled in a genotype-guided phase Ib study of irinotecan administered in combination with 5-fluorouracil/ leucovorin and bevacizumab.
Keywords: Pharmacokinetic, pharmacodynamics, phase I clinical study, colorectal cancer, Mass spectrometry, pharmacogenetics
Published in RUNG: 21.03.2017; Views: 4513; Downloads: 0
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56.
Thermal Lens Spectrometry and Microscopy Analytical Chemist’s Approach
Mladen Franko, unpublished invited conference lecture

Abstract: This lecture introduces the basic concepts and recent progres in theory, instrumentation and applications of thermal lens spectrometry, thermal lens microscopy and their utilization for highly sensitive, and high throughput detection in liquid chromatography, flow injectionanalysis in microfluidic systems.
Keywords: Thermal lens spectrometry, TLS microscopy, theory, applications
Published in RUNG: 01.03.2017; Views: 5249; Downloads: 1
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57.
RAPID UPLC-ESI-MS/MS BASED ASSAY FOR DISCOVERY OF UDP-N-ACETYLMURAMOYL-L-ALANINE:D-GLUTAMATE (MurD) LIGASE INHIBITORS
Vjekoslava Car, 2016, master's thesis

Abstract: A rapid, selective, robust and sensitive analytical assay method, operating in a short time frame with acceptable levels of precision, linear range and the accuracy necessary for successful Mur ligases inhibitors discovery, was developed. An LC-MS/MS analytical procedure was designed for the determination of a MurD ligase reaction product (UMAG). The special focus of this work was on UDP-N-acetylmuramyl-L-alanine:D-glutamate ligase (MurD) activity. The assay method is especially valuable as an orthogonal (secondary) assay for the primary high throughput fluorescent-based assay screening of potential Mur ligase inhibitors. The LC-MS/MS assay is fully compatible with the components from the primary fluorescent-based assay and enables the analysis of the same samples by both methodologies. The presented LC-MS/MS assay procedure is used for the evaluation of the false positive hits (molecules) from the primary, fluorescence based, high throughput screening assay experiments. This is important for the elimination of false positive hits from the prohibitively expensive and time-consuming investigation process. Method development describes the evaluation and optimization of the various stages of sample preparation, chromatographic separation, MS/MS determination and quantification. An enzyme reaction is performed in a 96-well plate. The quenched reaction mixture samples were spiked with an internal standard (phenacetin). The permeate was injected onto the U(H)PLC-MS/MS triple quadrupole system after sample ultrafiltration. Chromatographic separation was achieved on the ACQUITY UPLCTM HSS T3 column (100 x 2.1 mm i.d., 1.8 µm particle size) using an ammonium format buffer at pH 2.8 and acetonitrile as eluent. Elution initiated with an isocratic-hold for 1.1 min, followed by a two-step linear gradient of up to 3 min, giving a total run time of 5 min including equilibration. The flow rate was kept at a constant 0.4 mL/min. UMAG quantitative analysis was performed by positive electrospray ionization, followed by tandem mass spectrometry (ESI-MS/MS). The analytical assay quantifies UMAG in a linear range from 0.25 to 20 µM using 70 µL of samples. Validation results demonstrated that UMAG concentrations can be accurately and precisely determined in samples from the primary assay. Evaluation of inhibitory activities of compounds measured by both the fluorescence and the LC-MS/MS method demonstrated that the values were in a very good agreement. This analytical method can be used to screen a compound library at a defined concentration of each compound to obtain the percentage of inhibition, or with a series of compound concentrations to obtain inhibition potency of a compound (IC50). The selected Lek compounds no. 1 and 2 from the virtual screening campaign were presented, tested and further investigated due to the expression of significant MurD ligase inhibitory action acquired by primary high throughput tests. This assay has been developed for MurD, but during development, chromatographic and MS/MS conditions for UM and UMA were studied and defined as well. Therefore, this analytical assay method can easily be applied to other Mur ligases (i.e. MurC, MurE) enzyme activity monitoring in the process of bacteria cell wall peptidoglycan formation. This method enables the identification of many different Mur ligase inhibitors in a continued search for new Gram positive and Gram negative bacteria antibiotics.
Keywords: Mur ligases, UDP-N-acetylmuramyl-L-alanine:D-glutamate (MurD) inhibitors, UNAM-Ala-Glu, LC-MS/MS, liquid chromatography, tandem mass spectrometry, antibiotics, drug discovery
Published in RUNG: 23.09.2016; Views: 6817; Downloads: 273
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58.
Highly Sensitive Determination of Pyoverdine in Cloud Water by HPLC-Thermal Lens Spectrometry
Leja 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: 5481; Downloads: 0

59.
60.
Thermal Lens Spectrometry: Still a Technique on the Horizon
Mingqiang Liu, Mladen Franko, 2016, published scientific conference contribution

Abstract: In this article the historical development of thermal lens spectrometry (TLS) is briefly reviewed for introduction. In continuation, the emphasis is on the recent progresses of TLS for measurements in ensembled sample cells and in microfluidic flow injection systems. Novel theories, instrumentations and their applications for high sample throughput environmental, chemical and biomedical analysis, particularly in micro space, are presented. Discussions are given on the limitations of present TLS systems, that open new horizons for future progress of this technique, which has already found place among routine techniques for chemical analysis. In the last part, proposals for the future development of TLS toward advanced applications in new research fields are presented.
Keywords: Thermal lens spectrometry, Microfluidic chip, Chemical analysis, Environmental monitoring, Biomedical assay
Published in RUNG: 17.05.2016; Views: 4922; Downloads: 0
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