Radiochemiese en ioonchromatografiese metodes vir die bepaling van silwerhaliedkomplekse en haliedione in sout- en oliematrikse
- Authors: Taljaard, Immanda
- Date: 2014-03-12
- Subjects: Radiochemistry , Ion exchange chromatography , Chromatographic analysis , Silver halides , Halides
- Type: Thesis
- Identifier: uj:4311 , http://hdl.handle.net/10210/9663
- Description: M.Sc. (Chemistry) , The storage as solid Ag12BI(s) of reactor produced 12BI (t~ = 1.6 x 107 a) in underground respositories can present an environmental problem due to the potential release of radioactive 12BI into the environment over extended storage periods. One process that causes concern is the solubilization of AgI through complexation when brought into contact with underground water, particularly those with high salt content. In this work the charaqterization of the complexation equilibria in the AgI(s)/I-(aq),CI-(aq) system was studied. Solu- I tions containing high CI- and low 1- concentrations were of special interest with regard to the possible formation of ternary complexes. The presence of AgICI22- was indicated experimentally but no evidence of other ternary species like AgI2CI2- or AgIsCIS- could be established. Solubilities were determined radiochemically by using specially prepared 110mAgI. Solubility curves for AgI in different I-/CI- mixtures were adequately explained in terms of models consisting of the species AgCls2-, AgC14S-, AgIs2-, AgI4s- and AgICI22-. Distribution curves were calculated for different I-/CI- mixtures. As an alternative detection mode for silver-determination a flow injection system incorporating a micro-column of activated alumina was used in conjuntion with flame atomic absorption spectrometry for the pre-concentration and determination of silver in water. The procedure was successfully applied to a range of water samples, but no determination of silver in halide or perchlorate media was possible. The limit of detection based on a sample volume of 15 cms was 4.5 ~gdm-3 and the relative standard deviations at 50 and 5 ~gdm-3 were 5.4 and 19%, respectively. In part B of this work a method for the determination of chloride in organic compounds (oils provided by the Atomic Energy Corporation) by using an Parr oxygen bomb and ion chromatography was studied. The combustion products were absorbed in H20. The solution was injected into an ion chromatograph equipped with an anion analytical column, membrane suppressor and conductivity detector. The instrument response was calibrated using different standard solutions. These were prepared from several organic solutions, an organic salt and from sodiumchloride. Calibration curves were linear over a wide range and presented good reproducibility. It differed however according to the type of standard solution used. The limit of detection was 255 ~gdm-3 and the relative standard deviations at 10, 1 and 0.5 ugcm-3 were 0.52, 1.64 and 3.5%, respectively. As an alternative decomposition method wet decomposition within a sealed system (autoclave) was used. Due to the high blank values in this method no analysis of substances could be made in the lower ugcm-3 range.
- Full Text:
- Authors: Taljaard, Immanda
- Date: 2014-03-12
- Subjects: Radiochemistry , Ion exchange chromatography , Chromatographic analysis , Silver halides , Halides
- Type: Thesis
- Identifier: uj:4311 , http://hdl.handle.net/10210/9663
- Description: M.Sc. (Chemistry) , The storage as solid Ag12BI(s) of reactor produced 12BI (t~ = 1.6 x 107 a) in underground respositories can present an environmental problem due to the potential release of radioactive 12BI into the environment over extended storage periods. One process that causes concern is the solubilization of AgI through complexation when brought into contact with underground water, particularly those with high salt content. In this work the charaqterization of the complexation equilibria in the AgI(s)/I-(aq),CI-(aq) system was studied. Solu- I tions containing high CI- and low 1- concentrations were of special interest with regard to the possible formation of ternary complexes. The presence of AgICI22- was indicated experimentally but no evidence of other ternary species like AgI2CI2- or AgIsCIS- could be established. Solubilities were determined radiochemically by using specially prepared 110mAgI. Solubility curves for AgI in different I-/CI- mixtures were adequately explained in terms of models consisting of the species AgCls2-, AgC14S-, AgIs2-, AgI4s- and AgICI22-. Distribution curves were calculated for different I-/CI- mixtures. As an alternative detection mode for silver-determination a flow injection system incorporating a micro-column of activated alumina was used in conjuntion with flame atomic absorption spectrometry for the pre-concentration and determination of silver in water. The procedure was successfully applied to a range of water samples, but no determination of silver in halide or perchlorate media was possible. The limit of detection based on a sample volume of 15 cms was 4.5 ~gdm-3 and the relative standard deviations at 50 and 5 ~gdm-3 were 5.4 and 19%, respectively. In part B of this work a method for the determination of chloride in organic compounds (oils provided by the Atomic Energy Corporation) by using an Parr oxygen bomb and ion chromatography was studied. The combustion products were absorbed in H20. The solution was injected into an ion chromatograph equipped with an anion analytical column, membrane suppressor and conductivity detector. The instrument response was calibrated using different standard solutions. These were prepared from several organic solutions, an organic salt and from sodiumchloride. Calibration curves were linear over a wide range and presented good reproducibility. It differed however according to the type of standard solution used. The limit of detection was 255 ~gdm-3 and the relative standard deviations at 10, 1 and 0.5 ugcm-3 were 0.52, 1.64 and 3.5%, respectively. As an alternative decomposition method wet decomposition within a sealed system (autoclave) was used. Due to the high blank values in this method no analysis of substances could be made in the lower ugcm-3 range.
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Chromium speciation analysis by ion chromatography coupled with ICP-OES
- Authors: Jansen van Vuuren, Samantha
- Date: 2012-09-04
- Subjects: Speciation (Chemistry) , Chromium , Ion exchange chromatography , Chromatographic analysis , Inductively coupled plasma spectrometry
- Type: Thesis
- Identifier: uj:3510 , http://hdl.handle.net/10210/6899
- Description: M.Sc. , The behaviour i.e. the distribution, bioavailability and toxicity of an element depends on the particular species in which it is present. That being said the prediction of the behaviour of species can therefore not be predicted by determination of the total concentration alone. Speciation analysis is thus an important process, which seeks to identify and quantify the species that occur in a sample. By identifying the species one is better equipped to predict the behaviour of the element if it were released into the ecosystem as well as if it were used in industrial processes. The speciation analysis of the dominant chromium species, Cr(III) and Cr(VI), has received much attention as these contradictory species are involved in many industrial processes such as plating and tanning for example. The species have opposing behaviour as Cr(III) is found to be a necessary micronutrient for mammals where as Cr(VI) is known to be toxic. Of the numerous methods developed for chromium speciation analysis, the on-line process of chromatographic preconcentration followed by simultaneous detection with a sensitive detector produces a synergistic effect for the successful speciation analysis of chromium. It was thus decided to study ion chromatography hyphenated with an ICP-OES as a means of studying chromium species. Anion chromatography coupled with ICP-OES was the basis for the development of the first method. Complexation of Cr(III) with EDTA to form a monovalent anion preceded its separation from Cr(VI) as the chromate anion. A carbonate-bicarbonate eluent was used to elute the species from a Dionex AG 9 guard column coupled with an AS 9 separation column. This method proved to be effective and fast, with each analysis taking less than two minutes. The second method was based on cation chromatography in the form of a Dionex CG12A guard column being coupled with an ICP-OES spectrometer as the detector. This method made use of a gradient elution program in which hexavalent chromium was eluted first with ammonium nitrate followed by trivalent chromium with nitric acid. This method was successfully applied to synthetic samples and was found to be effective.
- Full Text:
- Authors: Jansen van Vuuren, Samantha
- Date: 2012-09-04
- Subjects: Speciation (Chemistry) , Chromium , Ion exchange chromatography , Chromatographic analysis , Inductively coupled plasma spectrometry
- Type: Thesis
- Identifier: uj:3510 , http://hdl.handle.net/10210/6899
- Description: M.Sc. , The behaviour i.e. the distribution, bioavailability and toxicity of an element depends on the particular species in which it is present. That being said the prediction of the behaviour of species can therefore not be predicted by determination of the total concentration alone. Speciation analysis is thus an important process, which seeks to identify and quantify the species that occur in a sample. By identifying the species one is better equipped to predict the behaviour of the element if it were released into the ecosystem as well as if it were used in industrial processes. The speciation analysis of the dominant chromium species, Cr(III) and Cr(VI), has received much attention as these contradictory species are involved in many industrial processes such as plating and tanning for example. The species have opposing behaviour as Cr(III) is found to be a necessary micronutrient for mammals where as Cr(VI) is known to be toxic. Of the numerous methods developed for chromium speciation analysis, the on-line process of chromatographic preconcentration followed by simultaneous detection with a sensitive detector produces a synergistic effect for the successful speciation analysis of chromium. It was thus decided to study ion chromatography hyphenated with an ICP-OES as a means of studying chromium species. Anion chromatography coupled with ICP-OES was the basis for the development of the first method. Complexation of Cr(III) with EDTA to form a monovalent anion preceded its separation from Cr(VI) as the chromate anion. A carbonate-bicarbonate eluent was used to elute the species from a Dionex AG 9 guard column coupled with an AS 9 separation column. This method proved to be effective and fast, with each analysis taking less than two minutes. The second method was based on cation chromatography in the form of a Dionex CG12A guard column being coupled with an ICP-OES spectrometer as the detector. This method made use of a gradient elution program in which hexavalent chromium was eluted first with ammonium nitrate followed by trivalent chromium with nitric acid. This method was successfully applied to synthetic samples and was found to be effective.
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