Analytical applications of ion selective devices

PhD ThesisIon selective electrodes, ISEs, and ion sensitive field effect transistors, ISFETs, are small, relatively simple to operate and easily automated sensors and, therefore, have a wide range of uses e. g. for field measurements in portable detectors, for on-line measurements in industrial flow systems and in clinical work. Several flow systems were studied for use with ion selective devices. New design ISE flow cells, designed at Newcastle, were found to minimise dead space and carry-over of sample solutions, allowing more rapid sample throughput. An ISFET flow cell studied, however, was found to have serious design faults. The constant volume dilution method of calibration and selectivity determination was shown to be a simple easy-touse method but must be implemented with caution. The selectivity of sensors to the primary ion was determined, where applicable, and the optical sensitivity of ISFETs was examined. Potassium concentrations in fertilizers were determined, using ISEs, in both flow systems described above; more accurate results were obtained using the newer flow-cells. Failure of ISEs after prolonged use in fertilizer solutions is believed to be have been caused by Donnan Breakdown due to HPO 2- ions. A computer controlled titration system was developed which can be used for volumetric or coulometric titrations. Coulometry, an absolute method, is particularly suitable for titration of sub micro-litre samples and for chemically labile species as sample manipulation is minimised and avoids addition of solution reagent, obviating CO 2 contamination of hydroxide. The advantages of coulometry were exploited in work to confirm the second dissociation constant for hydrogen sulphide. Aerial oxidation and sample carbon dioxide uptake are common problems associated with sulphide solutions. Using degassed water for sample preparation, keeping all solutions under nitrogen and using a sulphide anti-oxidant buffer it was possible to reduce sulphide oxidation. Coulometry was used to generate hydrogen ions and potentiometric measurements of the pH and sulphide ion concentrations, made simultaneously, were used to calculate the pK 2d of hydrogen sulphide for a range of 50 gl sodium sulphide solutions. A non-linear least squares programme, SUPERQUAD, was used to obtain a better value for pK 2d. Though a coulometric option exists in SUPERQUAD, it is not often implemented. ISE titration results have not been used much with SUPERQUAD; this work examined the potential of expanding the application of SUPERQUAD. Values of pK 2d of 12.08 ± 1.0 and 11.83 ± 0.4 were obtained by visual inspection and SUPERQUAD refinement, respectively. These values agree well with the text-book value, of 11.96, and demonstrate the accuracy of coulometry. The auto-titration system developed has advantages in many areas, particularly in clinical chemistry where determinations of available species in sub micro-litre samples, delivered in a flow system are required

Handbook of methods for the analysis of the various parameters of the carbon dioxide system in sea water. Version 2

The collection of extensive, reliable, oceanic carbon data is a key component of the Joint Global Ocean Flux Study (JGOFS). A portion of the US JGOFS oceanic carbon dioxide measurements will be made during the World Ocean Circulation Experiment Hydrographic Program. A science team has been formed to plan and coordinate the various activities needed to produce high quality oceanic carbon dioxide measurements under this program. This handbook was prepared at the request of, and with the active participation of, that science team. The procedures have been agreed on by the members of the science team and describe well tested methods. They are intended to provide standard operating procedures, together with an appropriate quality control plan, for measurements made as part of this survey. These are not the only measurement techniques in use for the parameters of the oceanic carbon system; however, they do represent the current state-of-the-art for ship-board measurements. In the end, the editors hope that this handbook can serve widely as a clear and unambiguous guide to other investigators who are setting up to analyze the various parameters of the carbon dioxide system in sea water

Guide to best practices for ocean CO2 measurements

CHAP 1 - Introduction to the Guide CHAP 2 - Solution chemistry of carbon dioxide in sea water CHAP 3 - Quality assurance CHAP 4 - Recommended standard operating procedures (SOPs) SOP 1 - Water sampling for the parameters of the oceanic carbon dioxide system SOP 2 - Determination of total dissolved inorganic carbon in sea water SOP 3a - Determination of total alkalinity in sea water using a closed-cell titration SOP 3b - Determination of total alkalinity in sea water using an open-cell titration SOP 4 - Determination of p(CO2) in air that is in equilibrium with a discrete sample of sea water SOP 5 - Determination of p(CO2) in air that is in equilibrium with a continuous stream of sea water SOP 6a - Determination of the pH of sea water using a glass/reference electrode cell SOP 6b - Determination of the pH of sea water using the indicator dye m-cresol purple SOP 7 - Determination of dissolved organic carbon and total dissolved nitrogen in sea water SOP 7 en Español - Determinacion de carbono organico disuelto y nitrogeno total disuelto en agua de mar SOP 11 - Gravimetric calibration of the volume of a gas loop using water SOP 12 - Gravimetric calibration of volume delivered using water SOP 13 - Gravimetric calibration of volume contained using water SOP 14 - Procedure for preparing sodium carbonate solutions for the calibration of coulometric CT measurements SOP 21 - Applying air buoyancy corrections SOP 22 - Preparation of control charts SOP 23 - Statistical techniques used in quality assessment SOP 24 - Calculation of the fugacity of carbon dioxide in the pure gas or in air CHAP 5 - Physical and thermodynamic data Errata - to the hard copy of the Guide to best practices for ocean CO2 measurement

Research and technology

As the NASA center responsible for assembly, checkout, servicing, launch, recovery, and operational support of Space Transportation System elements and payloads, Kennedy Space Center (KSC) is placing increasing emphasis on KSC's research and technology program. In addition to strengthening those areas of engineering and operations technology that contribute to safer, more efficient, and more economical execution of the current mission, the technological tools needed to execute KSC's mission relative to future programs are being developed. The Engineering Development Directorate encompasses most of the laboratories and other KSC resources that are key elements of research and technology program implementation and is responsible for implementation of the majority of the projects in this KSC 1990 annual report. Projects under the following topics are covered: (1) materials science; (2) hazardous emissions and contamination monitoring; (3) biosciences; (4) autonomous systems; (5) communications and control; (6) meteorology; (7) technology utilization; and (8) mechanics, structures, and cryogenics

Applications of dispersion in unsegmented flowing streams to calibration in atomic absorption spectrometry

Atomic absorption spectrometers require calibration because no absolute mathematical relationship exists between the analytical signal and the analyte concentration. The calibration function is complex, depending upon instrument parameters, operating conditions and the chemical nature of the sample matrix. Recalibration is necessary whenever these change. Because existing methods of calibration are tedious and sometimes inaccurate, alternatives are sought. Rapid, automated calibration is particularly attractive. The prospects of achieving it using concentration gradients generated in flowing streams, with microcomputer data processing, were investigated. [Continues.