Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 4 uppsatser.

Diss. (sammanfattning) Linköping : Univ., 2003. / Härtill 6 uppsatser.

Diss. Uppsala : Univ., 2005.

Diss. (sammanfattning) Karlstad : Karlstads universitet, 2008. / Härtill 5 uppsatser.

One of the strongest construction materials in relation to its weight is carbon fiber composites. The use of carbon fiber composites has increased substantially, for example in the automotive industry. Carbon fiber composites can decompose to respirable fibers and particles at high temperatures. The respirable fibers and particles can reach down to the alveoli in the lungs and cause inflammations. Respirable fibers have a diameter less than 3 μ m, a length longer than 5 μ m and a ratio between length and diameter equal to or greater than 3. Mechanical machining of carbon fiber composites decomposes the carbon fibers to inhalable fiber fragments with the original fiber diameter retained. Respirable fibers and fiber fragments can also transport other hazardous compounds or cause irritations on the skin and in the eyes. The aim of this study was to study the degree of contamination on protective clothes exposed to combustion or mechanical machining of carbon fiber composites. This to increase the understanding of the degree of contamination. The studied protective clothes were fire clothing from the emergency services in Karlskrona, disposable overalls used by the aircraft crash site group in the Swedish Armed Forces and lab coats used by Exova Materials Technology AB when mechanically machining carbon fiber composites. The protective clothes were washed after contamination to study how the contamination decreases after being washed. The contamination on the protective clothes were analyzed with GC - MS, microscopy and SEM. The conclusions from this study is that contamination of particles and fibers in varying sizes as well as gases are observed on the protective clothes, for example N,N - dimethyl formarmide and 1H,1H,2H,2H - perfluorooctan - 1-ol . Respirable fibers and particles were observed on the protective clothes after the combustion of carbon fiber composites. Washing the fire clothing and the lab coats eliminated the contamination. The contamination on the disposable overalls decreased after washing them, but did not eliminate the contamination completely

No description available.

Analytical chemical information is needed in all areas of human activity including health care, pharmacology, food control and environmental chemistry. Today one of the main challenges in analytical chemistry is the development of methods to perform accurate and sensitive rapid analysis and monitoring of analytes in ‘real’ samples. Electrochemical biosensors are ideally suited for these applications. Despite the wide application of electrochemical biosensors, they have some limitations. Thus, there is a demand on improvement of biosensor performance together with a necessity of simplification required for their mass production. In this thesis the work is focused on the development of electrochemical sensors with improved performance applicable for mass production, e.g. by screen printing. Biosensors using immobilized oxidases as the bio-recognition element are among the most widely used electrochemical devices. Electrical communication between redox enzymes and electrodes can be established by using natural or synthetic electron carriers as mediators. However, sensors based on soluble electronshuttling redox couples have low operational stability due to the leakage of water-soluble mediators to the solution. We have found a new hydrophobic mediator for oxidases – unsubstituted phenothiazine. Phenothiazine and glucose oxidase, lactate oxidase or cholesterol oxidase were successfully co-immobilized in a sol-gel membrane on a screen-printed electrode to construct glucose, lactate and cholesterol biosensors, respectively. All elaborated biosensors with phenothiazine as a mediator exhibited long-term operational stability. A kinetic study of the mediator has shown that phenothiazine is able to function as an efficient mediator in oxidase-based biosensors. To improve sensitivity of the biosensors and simplify their production we have developed a simple approach for production of graphite microelectrode arrays. Arrays of microband electrodes were produced by screen printing followed by scissor cutting, which enabled the realization of microband arrays at the cut edge. The analytical performance of the system is illustrated by the detection of ascorbic acid through direct oxidation and by detection of glucose using a phenothiazine mediated glucose biosensor. Both systems showed enhanced sensitivity due to improved mass transport. Moreover, the developed approach can be adapted to automated electrode recovery. Finally, two enzyme-based electrocatalytic systems with oxidation and reduction responses, respectively, have been combined into a fuel cell generating a current as an analytical output (a so-called self-powered biosensor). This was possible as a result of the development of the phenothiazine mediated enzyme electrodes, which enabled the  construction of a cholesterol biosensor with self-powered configuration. The biosensor generates a current when analyte (cholesterol) is added to the cell. The biosensor has been applied for whole plasma analysis. All developed concepts in the thesis are compatible with a wide range of applications and some of them may even be possible to realize in a fully integrated biosensor unit based on printed electronics.

Chemicals entering the market have been steadily increasing. The Swedish Chemicals Agency is in control of the Swedish Products Register, which is storing information on chemicals  manufactured in, transferred, or imported into Sweden. Applied to the register comes the exposure index predicting exposure of chemicals. For this study, the exposure index was used to make a first prioritization of chemicals with potential of exposure to consumers, the list of suspects were further prioritized by in silico predicted physiochemical properties. Six synthetic antioxidants 2,4-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, 2,4,6-tris-tert-butyl-phenol, 2,2´-methylene-bis(4-methyl-6-tert-butylphenol), 4,4´-methylene-bis(2,6-di-tert-butylphenol), octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenol) propionate), were selected for target analysis. Great care to background contamination is applied since the analytes are used in everyday objects such as food package and personal care products. Human serum samples was collected from “Blodcentralen” in Stockholm, Sweden. Previous analytical methods exist for individual and combination for a few analytes but lacks in combination of all selected analytes. A previous method for the extraction without clean-up of some of the analytes in serum were tested but lacked in efficiency for all analytes, hence an clean-up step for removal of lipids were added. A gas chromatography mass spectrometry method was developed for simultaneous analysis of the six analytes. Four of the target analytes were detected and three were quantified (2,4-di-tert-butylphenol 2.20-3.33 ng/mL, 2,6-di-tert-butyl-4-methylphenol 3.22-3.93 ng/mL and 2,4,6-tris-tert-butyl-phenol 0.054-0.104 ng/mL). 2,2´-methylene-bis(4-methyl-6-tert-butylphenol) was detected in high concentration but due to linearity problems (R2<0.99) it was not quantified. To the best of my knowledge this is the first time that 2,4,6-tri-tert-butylphenol and 2,2´- methylene-bis(4-methyl-6-tert-butylphenol) have been detected in human serum.

No description available.

This thesis presents two new concepts for separation of micro particles using dielectrophoresis, demonstrated by calculated examples, as well as a new method for obtaining dielectric data on living cells. The thesis is based on four papers. Paper I describes how the trapping efficiency of micro particles may be significantly increased when superpositioned electric fields are employed in a high conductivity medium. Avoiding low conductivity media is important when working with living cells. Calculations were performed to predict trajectories of Escherichia coli bacteria in the system with superpositioned electric fields, and a model was developed which employed two arrays of interdigitated electrodes in a micro channel. Paper II proposes a new concept for separation of micro particles, based on repetitive dielectrophoretic trapping and release in a flow system. Calculations show that the resolution increases as a direct function of the number of trap and release steps, and that a difference in size will have a larger influence on the separation than a difference in dielectrophoretic properties. Polystyrene beads in deionized water were used as a model, and calculations were performed to predict the particle behavior and the separation efficiency. It should be possible to separate particles with a size difference of 0.2 % by performing 200 trap-and-release steps. The enhanced separation power of multi step dielectrophoresis could have significant applications, not only for fractionation of particles with small differences in size, but also for measuring changes in surface conductivity. Paper III presents a new calculation method for predicting dielectrophoretic motion of micro particles. The method is based on a soft sphere method often used in molecular dynamics. Results from the calculations are in good agreement with theoretical predictions as well as initial experimental results, showing that the method provides good efficiency and accuracy. Paper IV describes a new method for measurements of conductivity of living bacteria. To obtain reliable conductivity values, it is important to handle the cells as gently as possible during the measurement process. A standard conductivity meter was used in combination with cross-flow filtration. In this way, repeated centrifugation and resuspension is avoided which otherwise may cause damage to the bacteria. The conductivity of Bacillus subtilis was determined to be 7000 μS/cm by means of the cross-flow filtration method, and the values differ from earlier published values by almost an order of a magnitude. In addition to the work presented in the papers, some experimental dielectrophoresis work in chip-based systems was performed. The behavior of Escherichia coli and polystyrene beads at different voltages and frequencies were studied. Separation of beads with different sizes was achieved on an array of interdigitated electrodes. Using electrodes with a pointed shape, alignment in different directions, pearl-chain formation, rotation, and other dielectrophoretic motion of E. coli were observed. / QC 20101108