Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.788538
Title: The role of ion exchange in the movement of chemicals through periderm and cuticular membranes
Author: Ersoz, Mustafa
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1993
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Abstract:
This thesis is principally an investigation on the factors contributing to the role of ion exchange in the movement of chemicals through the potato periderm and pear fruit cuticular membranes. This was investigated by monitoring the penetration of alkali cations, neutral amino acids and some pesticides through the potato periderm and pear fruit cuticular membranes in terms of physicochemical parameters such as permeability, diffusion, selectivity and adsorption by using the infinite-dose system, finite-dose and sorption process. Isolated cuticles or periderms, which represent the prime barrier to penetration, provide a physical system by which transport studies can be conducted under well defined and highly controlled conditions. Most studies with isolated cuticles have focused on sorption, desorption and infinite-dose cuticular transport of chemical compounds in aqueous systems. Transport systems, using isolated cuticles or periderms, may be used to quantify the effects of permeability, sorption, environmental pollutants, foliar absorption and spray additives on pesticide penetration. The work can be subdivided as follows: A brief discussion was made on the background chemistry, structure and ion exchange properties of potato periderm and pear fruit cuticles with regard to the use of chemicals on isolated membrane samples. The mechanisms of penetration of chemicals, the nature and chemistry of the potato periderm and pear fruit cuticles and some of the interacting factors contributing to variability were considered. The focus was on the use of potato periderm and pear fruit cuticles as model systems. The ion exchange properties and counter ion selectivity of the potato periderm and pear fruit cuticles towards alkali cations were studied. The important role of ion exchange, pretreatment and counter ion selectivity were demonstrated by results on the capacity and selectivity of alkali ions, which generally followed the order; Li+ > Na+ > K+ > Cs+. The ion exchange capacity and selectivity of the potato periderm and pear fruit cuticles depended on the different ionic forms, increasing with increasing pH and counter ion valence and decreasing with decreasing crystal radius. The titration curves obtained with NaOH in the presence of NaC1 depend markedly on pretreatment. Three separate groups can be distinguished over the pH ranges studied. Within these ranges, the first was between pH 3-5.5, the second between pH 5.5-9 and, the endpoint of the third group was estimated between pH 9-11.5. The isolated potato periderm and pear fruit cuticles exhibited a behaviour typical of highly cross-linked, high capacity ion exchange resins of the weak acid cation exchanger type. The adsorption equations obtained from plotting the experimental data gave a fair agreement with the Freundlich equation. Permeability and diffusion coefficients can be calculated from cuticular transport studies. These transport parameters provide a better understanding of the mechanisms of cuticular penetration phenomena. Further, they are useful when comparing both penetration characteristics of selected compounds and permeability studies. The details of penetration rates and the mechanisms of alkali cation uptake through the isolated potato periderm and pear fruit cuticles were determined. and the permeability and diffusion coefficients and, also from these parameters, relative values of permeability and diffusion coefficients were calculated.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.788538  DOI: Not available
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