An investigation of chemiluminescent miniaturised analytical systems
This thesis examines the feasibility of using chemiluminescence (CL) for detection in miniaturised analytical systems. The aim of this project was to design a miniaturised device that could potentially be used for the remote sensing of metal ions. The development of miniaturised analytical devices for use with two well known chemiluminescent reactions; namely the tris(2,2'-bipyridyl)ruthenium (II) reaction and the luminol reaction, for the detection and quantification of codeine and cobalt (II) respectively are discussed. Chapter 1 introduces the concept, the manufacture, operating principles and applications of miniaturised analytical systems, while the use of chemiluminescence, its requirements and applications as a sensitive, selective yet simple method of detection are reviewed in chapter 2. Chapter 3 describes the manufacture and development of the robust and practical miniaturised analytical devices used for the analyses described in chapters 4 and 5. Several novel developments are described in this chapter. These included the use of thicker top plates that enable the reservoirs to be contained within the single unit structure. This design was intended to prolong the lifetime of the chip system and increase the available reagent volumes. A microwave furnace for thermal bonding of the two glass plates was also used and the detection of the chemiluminesence produced in the chip system was carried out from underneath the chip base. Chapter 4 details the application of the tris(2,2'-bipyridyl)ruthenium (II) (TBR) for analysis in a miniaturised analytical system. This reaction was selected as a model chemiluminescence reaction for the optimisation of the detection system in order to measure the very low levels of light produced. The incorporation of non-ionic surfactants into the analysis and their effect on the enhancement of the chemiluminescence emission intensity and the modification of electroosmotic flow is discussed. A quantitative analysis of codeine was then successfully performed using this set-up. The points for the codeine concentrations of 5x10⁻⁷ to 1x10⁻⁴ mol 1⁻¹ were plotted to give a linear calibration plot. The equation of the line was y = 6.0136x + 0.0949, R2 = 0.9999, where x was the codeine concentration in mol 1⁻¹ and y was the mean CL emission intensity in mV. A limit of detection for codeine was determined at the 95% confidence limits to be 8.3x10-7 mol 1⁻¹ codeine, with an RSD of 8% (n=5) at the 5x10⁻⁵ mol 1⁻¹ level. The sample throughput time including removal of products and water wash was found to be an average of 2 minutes. The work described in chapter 5 builds on the findings of chapter 4 and examines the use of the luminol reaction in a miniaturised analysis system for the quantification of cobalt (II) ions. A multivariate experimental design programme was carried out as part of the work described in this chapter to simultaneously optimise most of the reagent variables. The application of cationic surfactants to this reaction in the miniaturised analysis system is also discussed, with particular emphasis on the observed enhancement of chemiluminescence emission intensity and lifetime, and the modification of the electroosmotic flow characteristics. A quantitative determination of cobalt nitrate was successfully carried out with a calibration over six orders of magnitude. The equation of the linear portion of the graph (10-10- 10-8 mol 1⁻¹) was found to be y = 64.625x + 735.71 with R2 = 0.999, where x (n=3) was the concentration in mol 1⁻¹ and y was the mean CL emission in mV. The limit of detection for cobalt nitrate at the 95% confidence limits was determined as -4x10⁻¹¹ mol 1⁻¹ which equates to 0.01 ng ml⁻¹ cobalt nitrate. An RSD of 6.9% (n=3) was obtained for the 1x10-8 mol 1⁻¹ standard. The sample run time was approximately 12 minutes, which resulted in an average overall throughput time of 15 minutes. The conclusions and ideas for future work are detailed in chapter 6.