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Opis: In 1980’s thermal lens spectrometry (TLS) was still considered as a “spectrometric technique on the horizon” as one can also read from one of the textbooks on spectrochemical analysis of that time. Intensive development of thermal lens instrumentation and methods of chemical analysis and material characterisation has however resulted in substantial progress in this field, which is evident from important instrumental innovations and first commercial instruments (i.e. thermal lens microscopes -TLM) designed for lab-on-a-chip chemistry as well as from novel applications of TLS in various areas, where highly sensitive and rapid chemical analysis of complex samples is needed, including food safety and quality control, environmental analysis and biomedical diagnostics. This presentation is a review of most significant contributions and applications of thermal lens spectrometry, with emphasis on most recent achievements in instrumentation, which culminated into construction of novel optimized TLM instruments, capable of exploiting the tuneability of incoherent light sources and enabled novel applications particularly in micro-fluidics. Based on latest progress relying on bio-analytical assays and micro-fluidic flow injection with TLM detection we have also witnessed firs routine applications of TLS in analytical and diagnostic laboratories, which on wine side actually classifies TLS as a conventional and routine analytical tool, but at the same time opens new horizons for development and applications of this ultrasensitive and rapid spectrometric technique.
Najdeno v: ključnih besedah
Povzetek najdenega: ...Thermal lens spectrometry, applications, Liquid chromatography, flow injection analysis, bioanalytical methods...
Ključne besede: Thermal lens spectrometry, applications, Liquid chromatography, flow injection analysis, bioanalytical methods
Objavljeno: 29.03.2016; Ogledov: 5258; Prenosov: 0
Polno besedilo (609,15 KB)

Opis: For more than five centuries, paper has been the predominant carrier of information and numerous medieval manuscripts bear witness of its durability. However, increasing demand for paper led to several changes in its production in the 19th century. High quality rag fibres were replaced by inferior wood-originating ones. Acid manufacturing technology was introduced which, due to its simplicity and low cost, continued to be used until the end of the 20th century. Inherently stable paper rapidly degrades in the presence of acids and its decay is further promoted by the poor storage conditions and environmental pollutants. As a result, the amount of degraded paper in libraries, archives and museums is reaching enormous proportions. In order to prolong the usable time of the vast quantities of original materials, paper collections may be deacidified and/or stored at lower temperatures. While preservation options are known, lack of the competent comparative studies leaves collection keepers hesitant of their use. The introductory part of the project is focused on development of analytical methodologies and model materials, representative of historical acid paper. As uniqueness and inherent value of cellulose-based cultural heritage limits the use of analytical methodologies to the non-destructive or micro-destructive ones. A new methodology for determination of the condition of paper was developed. The analytical technique-size exclusion chromatography for the first time allows us to reproducible determine the condition of paper which contains a significant amount of wood derived lignin. A few fibres suffice for the analysis, which renders the methodology suitable for characterisation of historical materials. The results of the research will represent the effect of deacidification processes with use of micro destructive analytical methodologies. As written word is all what we have for our legacy from generation to generation, evaluating preservation strategies for decaying collections, safekeeping and long term access to the endangered written cultural heritage is one of the most important facts.
Najdeno v: ključnih besedah
Ključne besede: paper, size exclusion chromatography, kinetics, deacidification process
Objavljeno: 02.09.2016; Ogledov: 5512; Prenosov: 267
Polno besedilo (1,33 MB)

Opis: 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.
Najdeno v: ključnih besedah
Povzetek najdenega: ...biogenic amines, NDA, liquid chromatography, TLS, fluorescence, wine...
Ključne besede: biogenic amines, NDA, liquid chromatography, TLS, fluorescence, wine
Objavljeno: 02.11.2017; Ogledov: 3681; Prenosov: 253
Polno besedilo (441,06 KB)

Opis: Environmental pollution in the 21th century still represents a global problem for human and animal health. Despite general awareness about released substances and their degradation products their fate and possibilities of removal are not well investigated. Even though the chemicals released are dispersed and diluted in water cycles, their poor biodegradability and/or strong accumulation can result in the intoxication of exposed organisms. Similarly, as a part of the environment, food can get contaminated by bioactive substances during different steps of preparation. Not only artificial compounds such as pesticides or pharmaceuticals, but also natural toxins enter the food chain and impact negatively on humans' and animals' health. In addition, the activity of some bacteria can influence the production of amines from amino acids after fermentation, to which the human body responds with several symptoms of intoxication. Several analytical methods for the determination of trace levels of broad range contaminants have been developed. Due to the largely robust, selective and sensitive features of the conventional (rearguard) techniques, they represent the first choice for analysing multiple organic compounds in frequently very complex matrices. However, screening (vanguard) methods are paving the way in the chemical analytics as a solution that provides simplicity and rapid analytical responses with binary (yes/no) answers. They require little or no sample treatment as well as more economically-efficient instrumentation. The combination of vanguard-rearguard analytical strategies hence offers a compromise between classical analytical figures of merit and productivity-related characteristics. In the first part of our research feasibility studies for the application of TLS and/or TLM in novel analytical methods for the determination of lipid-lowering drug atorvastatin and a mycotoxin ochratoxin A . The survey on atorvastatin performed spectrophotometrically has shown a decrease of ATV-sulpho-vanillin product at the wavelength of its maximum absorbance after dilution by organic solvent, which was investigated due to the possible increasing of the method sensitivity. As the predicted LODs that could be obtained by TLM (0.3 mg/L) could not reach the concentration of ATV usually present in the environment (ng/L-g/L) further experiments on this subject were therefore not justified. On the other hand, the ELISA assay for the determination of ochratoxin A was performed. In case of μFIA-TLM, the measurements were influenced by high background signal resulting in high LODs of TLM (470 pg/mL), which is known as a background limited technique. It was estimated that the LODs of standard ELISA assay could not be significantly improved, therefore no further research was conducted in this direction. In the second part of the dissertation, a sensitive rearguard system by coupling HPLC and TLS for the determination of biogenic amines in wine samples was developed. Putrescine, cadaverine, histamine and tyramine were separated and detected on a HPLC-TLS system after derivatization by dabsyl chloride. The method was optimized in terms of chromatographic conditions and in terms of TLS parameters. Also, the sensitivity of the newly developed method was evaluated by comparing the TLS detection with DAD detection in terms of LOD values, where TLS showed 3.6-fold improvement compared to DAD. Afterwards, the standard addition calibration was performed and evaluated for its recoveries (86−117%) in the determination of the four BAs. The applicability of the novel method was tested by the analysis of real white and red wine samples and by comparing the results to the standard HPLC-FL method and concentrations of BAs in wine samples were in good accordance. In addition, the dabsylated BAs showed better stability compared to the OPA derivatives as they have not lost the peak intensity after 17h of storage. In the third part, a vanguard system for detection of the overall biogenic amines concentration was developed by employing μFIA-TLM. Initially, NH4Cl standard solutions were applied in the indophenol reaction for batch mode, off-line μFIA-TLM and in an on-line indophenol formation for μFIA-TLM detection. By adding 50 % of EtOH to indophenol we obtained 9-fold improvement. In addition, indophenol showed good stability under TLM conditions. We optimized the microfluidic and TLM parameters in the off-line and on-line indophenol reaction. The addition of 5% ethanol to the reagent in the on-line reaction resulted in the 3-fold improvement of the signal-to-noise ratio. Further on, the overall reaction, including the enzymatic and the following indophenol reaction, was optimized by choosing the optimal buffer (pH=7, 0.5 M) and alkaline conditions (2M NaOH). The influence of interferences from amino compounds was also evaluated and discussed. The off-line and on-line μFIA-TLM were evaluated by their performance characteristics. The LOD for ammonia detection reached 2.3 μM and the applicability in ammonia detection in water samples was discussed. Similar LOD of 3.2 μM was obtained for the overall concentration of BAs and LOD of 3.8 μM for histamine, which is more than 4-folds lower value as the lowest suggested limits of intake for histamine in wine samples (2 mg/L; 18 μM). Finally, an immobilization procedure on magnetic nanoparticles was developed for the possible implementation of the selected enzyme in a miniaturized biosensor.
Najdeno v: ključnih besedah
Povzetek najdenega: ...spectrometry, thermal lens microscopy, high performance liquid chromatography, microfluidics, biogenic amines, microbial transglutaminase, indophenol (Berthel...
Ključne besede: thermal lens spectrometry, thermal lens microscopy, high performance liquid chromatography, microfluidics, biogenic amines, microbial transglutaminase, indophenol (Berthelot) reaction
Objavljeno: 04.06.2018; Ogledov: 3955; Prenosov: 237
Polno besedilo (2,90 MB)

Opis: The mixing ratios of 11 C1–C3 halocarbons have been measured using a GC–twin‐linked ECD system over the period from October 2004 to December 2005 at an urban site in Bristol, UK. Time series and seasonal variations of the halocarbons were analysed over the period to determine biogenic and anthropogenic sources and sinks. Correlations between the target halocarbons were also observed, suggesting common sources within the area. Wind rose plots for all halocarbons have been used to assist in the determination of halocarbons sources. Halocarbon concentrations are highest at low‐wind speeds and decrease as wind speed increases, a few species (CCl4 and CH3Cl most notably) rise at very high‐wind speeds suggesting release from the Bristol Channel.
Najdeno v: ključnih besedah
Povzetek najdenega: ...halocarbons, biogenic halocarbons, electron capture detector, gas chromatography, methyl bromide...
Ključne besede: adsorption–desorption system, anthropogenic halocarbons, biogenic halocarbons, electron capture detector, gas chromatography, methyl bromide
Objavljeno: 18.07.2019; Ogledov: 2166; Prenosov: 0
Polno besedilo (897,06 KB)