Medical diagnosis and treatment of critically ill patients require frequent monitoring of carbon dioxide partial pressure in the human body. Along with the traditional methods (i.e. IR capnography and Severinghaus electrode), colorimetric and fluorimetric CO<SUB>2</SUB> sensors are playing an increasingly important role in detection of correct intubation, intensive care and blood CO<SUB>2</SUB> analysis, due to its advantages of cheapness in cost, miniature in size, and mechanically robust. In Chapter One an outline of the recent development of such sensor systems is given, and their applications background in the biomedical area is discussed. Chapter Two focuses on the experimental techniques used in these studies. In Chapters Three and Four the equilibrium responses of three new colorimetric and one fluorescence plastic film sensors for CO<SUB>2</SUB> as a function of % CO<SUB>2</SUB> and temperature are described, respectively. The results fit a model in which there is a 1:1 equilibrium reaction between the deprotonated form of the dye (present in the film as an ion pair) and CO<SUB>2</SUB>. The basic theory behind conventional colorimetric and fluorimetric optical sensors for CO<SUB>2</SUB> is proposed and examined in Chapter Five. Special attention is given to the effect on sensor response of the key parameters of initial base concentration and dye acid dissociation constant, K<SUB>D</SUB>. In Chapter Six the diffusion-controlled response and recovery behaviour of a naked optical film sensor with a hyperbolic-type reponse changes in analyte concentration in a system under test is approximated using a numerical model, followed by a second part in which a systematic, experimental investigation on the kinetics, responses and recovery behaviour of the colorimetric film sensors is described. Finally, in Chapter Seven, a plasticised and unplasticised polymer colorimetric film sensor for gaseous CO<SUB>2</SUB> is tested as a sensor for dissolved CO<SUB>2</SUB>. The plasticised form of the film sensor develops a measurable degree of opacity when exposed to aqueous solution, while an unplasticised polymer remains largely clear upon exposure to aqueous solution and it is shown that it also functions as a quantitative sensor for dissolved CO<SUB>2</SUB> over the range 0-4% CO<SUB>2</SUB>.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:636226 |
| Date | January 1993 |
| Creators | Chang, Q. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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