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Metal chelation in separation science

Deacon, Marian (1994) Metal chelation in separation science. PhD thesis, Dublin City University.

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Abstract

The science o f transition metal chelation finds applicability in many analytical areas where the determination of agents which will chelate transition metal ions, or the determination of transition metal ions themselves, is desired. This thesis details the use of transition metal chelation in solving analytical problems encountered in the adhesives, fertiliser and biomedical laboratoiy. In the adhesives industry, transition metal ions in anaerobic adhesives can initiate the polymerisation process, resulting in premature setting o f products in their packaging. Addition o f a chelating agent such as ethylenediaminetetraacetic acid, however, renders the metal ion inactive with respect to its catalytic properties. A novel method was developed for the simultaneous determination o f the seven metal cations Cu(II), Pb(II), Ni(II), Zn(II), Co(II), Cd(H), and Mn(H), with limits o f detection as low as 30 ppb for certain metal ions. The method has been shown to give no response in the presence of excess EDTA This was achieved by the development o f a solid-phase extraction procedure, and separation on a dynamically coated Cjg reversed-phase highperformance liquid chromatography column. In the fertiliser industry, chelates are added to commercial fertilisers for the supply of micronutrients to plants. The determination of the iron chelates of ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), hydroxy-2- ethylenediaminetriacetic acid (HEEDTA), ethylenediaminedi(o-hydroxy-phenylacetic) acid (EDDHA), and ethylenediaminedi(o-hydroxy-p-methylphenyl) acetic acid (EDDHMA), and the Cu, Zn and Mn chelates of EDTA was investigated. The ionpairing reagent tetrabutylammonium hydroxide, gave a separation of all iron chelates on a Chromspher C jg column using a solvent switching system. Cu-, Zn-, and MnEDTA were separated using the ion-pairing reagent tetradecyltrimethylammonium bromide. For the iron chelates both limit of determination and linear range studies, showed that the method is capable of analysing the concentration range found in commercial fertilisers. The capabilities of gel permeation chromatography for the separation and purification of the above chelates, was also investigated. Of the two gels Bio-Gel P2 and Fractogel HW-40 (S), Fractogel HW40 (S) gave the best separation o f FeEDDHA, FeEDDHMA, FeDTPA and FeHEEDTA. CuEDTA, ZnEDTA and MnEDTA were found to co-elute with FeDTPA. Capillary electrophoresis (CE) has become very important in the analysis o f peptides, as it is a highly powerful mechanism of separation, and can analyse nanoliter sample quantities. However, detection methods employing UV, spectrofluorimetry, radiolabelling and mass spectrometry have limited sensitivity. A copper-coated capillary was developed for the determination of peptides by CE with electrochemical detection. A simple washing procedure produces a copper-coated column which is stable for 12 hours. Under alkaline conditions, peptides complex with Cu(II) from the walls of the column to form Cu(II)-peptide complexes which are subsequently oxidised at a carbon fibre electrode to form copper(III)-peptides. The system was shown to be applicable for the analysis of small peptides (five amino acids),and protected peptides, for which typical detection limits were in the lx lO 'range.

Item Type:Thesis (PhD)
Date of Award:1994
Refereed:No
Supervisor(s):Smyth, Malcolm R.
Uncontrolled Keywords:Chelates; Separation science
Subjects:Physical Sciences > Analytical chemistry
Physical Sciences > Chemistry
DCU Faculties and Centres:DCU Faculties and Schools > Faculty of Science and Health > School of Chemical Sciences
Use License:This item is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 3.0 License. View License
ID Code:18486
Deposited On:19 Jul 2013 11:41 by Celine Campbell. Last Modified 19 Jul 2013 11:41

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