This thesis describes the application of a microcomputer to the development of automatic analytical instrumentation. The basic structure of a typical microcomputer and the manner in which it is programmed are described, and the applications of microprocessors to analytical instrumentation are reviewed. The remainder of the thesis is devoted to detailed description of the stages involved in the development of an Automatic Titrator and an Automatic Viscometer; the microcomputer is used to both control the equipment and process the results. The computer-controlled titrator was developed for the sequential titration of a mixture of adipic acid and boric acid against sodium hydroxide for use in the manufacture of Nylon. The differential plot Apll/ OV is used for the determination of end-points. The effect on the results of varying several experimental parameters were examined. These included the orientation of the titrant delivery tube, stirring speed, and the time interval between the addition of titrant and recording the ADC reading. The accuracy and precision of the results obtained with the computer-controlled system compare favourably with the conventional titrator which titrates to present pH values. The instrument has been developed further to become one of general applicability. Attention was then turned to the development of an instrument for the determination of molecular weights of polymers, based on the measurement of viscosity. Two approaches were adopted: 1. Timing the rise of very small bubbles through the liquid medium of unknown viscosity; 2. Injecting a slug of liquid into a liquid flowing in a capillary tube and measuring the extent of dispersion and/or the viscous drag. In the first of these, considerable practical difficulties were encountered. The second approach was experimentally simple, and was adopted. Taylor proposed that the dispersion of the sample is a consequence of diffusion and the effect of the fluid flowing along the capillary. When the flow-rate is sufficiently slow, dispersion is predominantly by diffusion and formulae are derived which describe the sample concentration profile in terms of the diffusion coefficient of the sample into the carrier. Viscosity is related to the diffusion coefficient by the Stokes-Einstein equation. When dispersion is predominantly a consequence of fluid flow, then, according to Poiseuille's equation, the time between injection and detection is related to the viscosity of the sample. Both theories have been verified for several systems. Smooth calibration curves may be obtained for a given system. Sample volumes of 6:2 have been employed and measurements are typically made in less than one minute. The microcomputer is used to control the injection of samples and to measure the maximum concentration at the detector and the corresponding time from injection. The system has also been used for the determination of diffusion coefficients of a sample of orange oil into various solvents.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:636356 |
| Date | January 1978 |
| Creators | David, P. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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