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Jonathan W. Steed - One of the best experts on this subject based on the ideXlab platform.
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Supramolecular Gelation as the First Stage in Ostwald’s Rule
Crystal Growth & Design, 2018Co-Authors: Jessica L. Andrews, Jonathan W. Steed, Emma Pearson, Dmitry S. Yufit, Katharina EdkinsAbstract:Ostwald’s rule of stages describes the observation that a metastable polymorph of a particular compound will crystallize before the thermodynamically stable form under the same conditions. While traditionally applied to crystalline systems, there have been recent examples in which noncrystalline supramolecular assemblies transform according to this rule. In this work we report the highly selective organogelation behavior of a monoiodinated 2,4,5-triphenylimidazole (lophine) derivative (I-TPI). The gel emerges as a kinetically trapped intermediate, prior to the crystallization of a series of increasingly stable methanol solvates. As such, we describe the supramolecular gel as a precrystalline phase, representing the first of Ostwald’s stages for this system. Similar behavior can be observed when the gel is used as a medium for pharmaceutical crystallization of Diatrizoic Acid (DTA). In this case, two solid forms are produced, both containing molecules of DTA, I-TPI, and methanol in different stoichiometrie...
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Supramolecular Gelation as the First Stage in Ostwald’s Rule
2018Co-Authors: Jessica L. Andrews, Jonathan W. Steed, Emma Pearson, Dmitry S. Yufit, Katharina EdkinsAbstract:Ostwald’s rule of stages describes the observation that a metastable polymorph of a particular compound will crystallize before the thermodynamically stable form under the same conditions. While traditionally applied to crystalline systems, there have been recent examples in which noncrystalline supramolecular assemblies transform according to this rule. In this work we report the highly selective organogelation behavior of a monoiodinated 2,4,5-triphenylimidazole (lophine) derivative (I-TPI). The gel emerges as a kinetically trapped intermediate, prior to the crystallization of a series of increasingly stable methanol solvates. As such, we describe the supramolecular gel as a precrystalline phase, representing the first of Ostwald’s stages for this system. Similar behavior can be observed when the gel is used as a medium for pharmaceutical crystallization of Diatrizoic Acid (DTA). In this case, two solid forms are produced, both containing molecules of DTA, I-TPI, and methanol in different stoichiometries, and once again crystallizing in sequence according to Ostwald’s rule. These results demonstrate that supramolecular gelation may be considered the first stage in the stepwise crystallization of a gelator, as governed by Ostwald’s rule, and that this behavior also applies to multicomponent systems, facilitating the production of metastable pharmaceutical solid forms
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Insights into the crystallisation process from anhydrous, hydrated and solvated crystal forms of Diatrizoic Acid
Chemistry (Weinheim an der Bergstrasse Germany), 2014Co-Authors: Katharina Fucke, Judith A. K. Howard, Garry J. Mcintyre, Marie Helene Lemee-cailleau, C. Wilkinson, Alison J. Edwards, Jonathan W. SteedAbstract:Diatrizoic Acid (DTA), a clinically used X-ray contrast agent, crystallises in two hydrated, three anhydrous and nine solvated solid forms, all of which have been characterised by X-ray crystallography. Single-crystal neutron structures of DTA dihydrate and monosodium DTA tetrahydrate have been determined. All of the solid-state structures have been analysed using partial atomic charges and hardness algorithm (PACHA) calculations. Even though in general all DTA crystal forms reveal similar intermolecular interactions, the overall crystal packing differs considerably from form to form. The water of the dihydrate is encapsulated between a pair of host molecules, which calculations reveal to be an extraordinarily stable motif. DTA presents functionalities that enable hydrogen and halogen bonding, and whilst an extended hydrogen-bonding network is realised in all crystal forms, halogen bonding is not present in the hydrated crystal forms. This is due to the formation of a hydrogen-bonding network based on individual enclosed water squares, which is not amenable to the concomitant formation of halogen bonds. The main interaction in the solvates involves the carboxylic Acid, which corroborates the hypothesis that this strong interaction is the last one to be broken during the crystal desolvation and nucleation process.
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Overcoming the solvation shell during the crystallisation of Diatrizoic Acid from dimethylsulfoxide
Chemical communications (Cambridge England), 2012Co-Authors: Katharina Fucke, Judith A. K. Howard, Jonathan W. SteedAbstract:We present three crystal structures of Diatrizoic Acid (DTA) DMSO solvates illustrating progressive desolvation of the DTA molecule and concomitant increasing degree of DTA self-association. Using these structures, plausible pathways for overcoming the solvation shell of DTA during its crystallisation from solution are discussed.
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A new water... Na+ coordination motif in an unexpected Diatrizoic Acid disodium salt crystal form
Chemical communications (Cambridge England), 2012Co-Authors: Katharina Fucke, Judith A. K. Howard, Michael J. G. Peach, Jonathan W. SteedAbstract:The disodium salt of Diatrizoic Acid crystallises as a tetragonal channel hydrate structure. One of the incorporated water molecules is coordinated to three individual sodium cations in a unique geometry.
Wolfram. Seitz - One of the best experts on this subject based on the ideXlab platform.
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Formation of oxidation by-products of the iodinated X-ray contrast medium iomeprol during ozonation.
Chemosphere, 2007Co-Authors: Wolfram. Seitz, Jia-qian Jiang, Walter H. Weber, Dietrich Maier, Wolfgang Schulz, Matthias MaierAbstract:The present work describes the investigation of the formation of oxidation by-products of the iodinated X-ray contrast medium (ICM) iomeprol during ozonation in water treatment. Bench-scale investigations revealed that ICM can be partly oxidized during ozonation processes, whereas the ionic Diatrizoic Acid showed the lowest reactivity. Iomeprol, as a representative of ICM, was not fully mineralized during ozonation. Thus, unknown oxidation by-products were formed. Aqueous solutions of iomeprol were treated by ozonation in order to assess the formation of oxidation by-products. The by-products were characterized by different liquid chromatography methods including detection of single-stage mass spectra, product ion mass spectra, and induced in-source fragmentation for analysis of iodine containing oxidation by-products. Aldehyde and carbonyl containing compounds were proposed to be among the stable by-products. A derivatization step confirms that the aldehyde and carbonyl moieties are major functional groups in oxidation by-products of iomeprol. Furthermore, oxidation by-products of iomeprol were detected at the outlet of an ozone reactor at a full-scale waterworks. However, the toxicological relevance of the by-products is a major future research tasks.
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Occurrence and behaviour of iodinated X-ray contrast media in drinking and waste water treatment
2007Co-Authors: Wolfram. SeitzAbstract:Main objective of the present work was to contribute to a detailed understanding of the occurrence and behaviour of iodinated X-ray contrast media (ICM) in waste and drinking water treatment. In particular, the behaviour of five ICM compounds during ozonation for drinking water treatment and the use of activated carbon for the removal of ICM during wastewater treatment was investigated. In addition, the occurrence of the compounds in the raw and drinking waters was studied. The availability of sensitive and accurate analytical methods for the determination of ICM was an indispensable requirement. Therefore, different methods using HPLC-MS instruments including electrospray ionisation were developed. This included a direct detection method using a triple quadrupole mass spectrometer for ICM in water. The limits of detection were below 50 ng.l-1. In addition, it was possible to pre-concentrate the compounds by solid phase extraction. Furthermore, an iodine-specific method in order to screen for unknown oxidation by-products or metabolites of the iodinated compounds was developed. A monitoring programme was carried out in order to study the occurrence of ICM in the ground water of the Danube Reed and the surface water abstracted from the river Danube. Traces of a few ng l-1 of non-ionic ICM were detected in the ground water, whereas the maximum concentration of Diatrizoic Acid was 45 ng.l-1. In contrast, over 500 ng.l-1 for Diatrizoic Acid and iopami-dol were found in the Danube. By means of a concentration profile peaks were recorded, whereas the highest concentrations were generally observed on weekdays. Furthermore, it was shown that the elimination rate for the non-ionic ICM was approximately 70% at Langenau waterworks. In particular, intermediate ozonation could remove 33% and granulated activated carbon filtration achieved 50% in average. However, Diatrizoic Acid was not removed significantly. The maximum concentrations of iomeprol, iopamidol and Diatrizoic Acid were over 100 ng-1 in the finished drinking water. In addition, it could be demonstrated that 28% to 46% of the ICM compounds were removed during conventional wastewater treatment at sewage treatment plant of Ulm and Neu-Ulm. However, the highest removal rate of 71 % in average was found for iopromide. The average concentrations of ICM in the final effluent ranged between 3.5 μg l-1 for iohexol and 24 μg l-1 for iomeprol. Moreover, the application of powdered activated carbon (PAC) to remove ICM from the effluent proved to be efficient. The removal percentages for iomeprol, iopromide and iohexol were between 77% and 86%, but that for iopamidol was 49% in average for an addition of 10 mg l-1 PAC. In contrast, Diatrizoic was only slightly removed by the PAC treatment. Furthermore, the behaviour of ICM during ozonation was investigated in bench-scale studies. Hydroxyl radicals proved to be the major oxidant. It was shown that a complete removal of ICM in pre-treated surface water by ozonation cannot be achieved at moderate ozone concentrations, contact times and realistic pH values. Diatrizoic Acid was not eliminated significantly. In general, the compounds should not be mineralised during the ozonation at Langenau waterworks. However, two oxidation by-products of iomeprol could be detected and tentatively identified at Langenau waterworks, which had no significant luminescence inhibition effect towards Vibrio fischeri. In contrast, luminescence inhibition was detected from by-products after UV treatment process of ICM containing wastewater. However, the ICM concentrations in the wastewater were significantly higher than in pre-treated surface water. Therefore, it is reasonable to initiate investigations addressing the toxicological relevance of the by-products.
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Monitoring of iodinated X-ray contrast media in surface water.
Chemosphere, 2006Co-Authors: Wolfram. Seitz, Jia-qian Jiang, Walter H. Weber, B.j. Lloyd, Matthias Maier, Dietrich Maier, Wolfgang SchulzAbstract:A monitoring programme was carried out in order to determine iodinated X-ray contrast media (ICM) in the River Danube and to investigate the raw water quality for drinking water production at Langenau waterworks. The study revealed that the maximum concentrations of ICM (over 500 ng l−1 for Diatrizoic Acid and iopamidol) were found in 2 h-composite samples taken from the downstream of the Ulm/Neu-Ulm metropolitan area. By means of a concentration profile over one month the highest ICM concentrations were observed on weekdays. The extended data evaluation with principal component analysis shows that the upstream and downstream samples had different pattern of variations in ICM concentration and also demonstrates a clear change in ICM composition by the discharge of municipal wastewater. In addition to load profiles of ICM, time-dependent plots of principal component 1 exhibited peaks, indicating a short-term discharge of ICM between the two sampling sites. In conclusion, a point source for ICM contamination between the sampling sites in Ulm upstream and Leipheim downstream seems to be the reasonable explanation for peak ICM concentrations. Due to the observed high variations of ICM concentrations in river, the evaluation of natural waters by means of a single analysis is not representative.
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Removal of Iodinated X-Ray Contrast Media During Drinking Water Treatment
Environmental Chemistry, 2006Co-Authors: Wolfram. Seitz, Jia-qian Jiang, Walter H. Weber, B.j. Lloyd, Matthias Maier, Dietrich MaierAbstract:Environmental Context.In recent years, many micro-organic pollutants, e.g. pharmaceuticals and personal care products (PPCP), have been observed to be persisting through wastewater treatment and occurring in the environment. Persistent micropollutants are of particular concern owing to the fact that some of them have been found in drinking water, and iodinated X-ray contrast media (ICM) are one group of such pollutants. Abstract.The present study investigates the removal of five iodinated X-ray contrast media (ICM) during drinking water production from surface water at a full-scale water works, which comprises coagulation/flocculation, intermediate ozonation, in-line filtration and adsorption with activated carbon. The elimination rates over all treatment units for the non-ionic ICM (iomeprol, iopromide, iohexol and iopamidol) were determined to be approximately 70%. In particular, intermediate ozonation can remove 30% on average of the non-ionic ICM, whereas it cannot remove the ionic Diatrizoic Acid, and the granulated activated carbon filters can achieve a further 50% removal of non-ionic ICM. However, over 100 ng L−1 of ionic Diatrizoic Acid and 40–100 ng L−1 of non-ionic ICM were found in the produced drinking water.
Katharina Edkins - One of the best experts on this subject based on the ideXlab platform.
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Supramolecular Gelation as the First Stage in Ostwald’s Rule
Crystal Growth & Design, 2018Co-Authors: Jessica L. Andrews, Jonathan W. Steed, Emma Pearson, Dmitry S. Yufit, Katharina EdkinsAbstract:Ostwald’s rule of stages describes the observation that a metastable polymorph of a particular compound will crystallize before the thermodynamically stable form under the same conditions. While traditionally applied to crystalline systems, there have been recent examples in which noncrystalline supramolecular assemblies transform according to this rule. In this work we report the highly selective organogelation behavior of a monoiodinated 2,4,5-triphenylimidazole (lophine) derivative (I-TPI). The gel emerges as a kinetically trapped intermediate, prior to the crystallization of a series of increasingly stable methanol solvates. As such, we describe the supramolecular gel as a precrystalline phase, representing the first of Ostwald’s stages for this system. Similar behavior can be observed when the gel is used as a medium for pharmaceutical crystallization of Diatrizoic Acid (DTA). In this case, two solid forms are produced, both containing molecules of DTA, I-TPI, and methanol in different stoichiometrie...
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Supramolecular Gelation as the First Stage in Ostwald’s Rule
2018Co-Authors: Jessica L. Andrews, Jonathan W. Steed, Emma Pearson, Dmitry S. Yufit, Katharina EdkinsAbstract:Ostwald’s rule of stages describes the observation that a metastable polymorph of a particular compound will crystallize before the thermodynamically stable form under the same conditions. While traditionally applied to crystalline systems, there have been recent examples in which noncrystalline supramolecular assemblies transform according to this rule. In this work we report the highly selective organogelation behavior of a monoiodinated 2,4,5-triphenylimidazole (lophine) derivative (I-TPI). The gel emerges as a kinetically trapped intermediate, prior to the crystallization of a series of increasingly stable methanol solvates. As such, we describe the supramolecular gel as a precrystalline phase, representing the first of Ostwald’s stages for this system. Similar behavior can be observed when the gel is used as a medium for pharmaceutical crystallization of Diatrizoic Acid (DTA). In this case, two solid forms are produced, both containing molecules of DTA, I-TPI, and methanol in different stoichiometries, and once again crystallizing in sequence according to Ostwald’s rule. These results demonstrate that supramolecular gelation may be considered the first stage in the stepwise crystallization of a gelator, as governed by Ostwald’s rule, and that this behavior also applies to multicomponent systems, facilitating the production of metastable pharmaceutical solid forms
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the complex solid state landscape of sodium diatrizoate hydrates
Chemistry: A European Journal, 2017Co-Authors: Mohd Nadzri Mohd Najib, Kevin Back, Katharina EdkinsAbstract:Pharmaceutical sodium salts are prone to incorporate water into their crystal structures. The model compound Diatrizoic Acid monosodium salt, an X-ray contrast agent, has been investigated in depth towards its interaction with water in the solid state. Five hydrates with water content ranging from 0.3 to 8 molar equivalents of water show a high degree of interconvertibility, stoichiometric and non-stoichiometric behaviour, and potential of amorphisation during release of water. A DMSO/water mixed solvate further highlights the high attraction of this salt to incorporate water. All incorporated solvent coordinates to the sodium cation and can further interact and stabilise the respective crystal forms by hydrogen bonding. DTS thus highlights the importance of an in-depth investigation of sodium salts used pharmaceutically to guarantee dose uniformity and stability of final formulation.
Dietrich Maier - One of the best experts on this subject based on the ideXlab platform.
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Formation of oxidation by-products of the iodinated X-ray contrast medium iomeprol during ozonation.
Chemosphere, 2007Co-Authors: Wolfram. Seitz, Jia-qian Jiang, Walter H. Weber, Dietrich Maier, Wolfgang Schulz, Matthias MaierAbstract:The present work describes the investigation of the formation of oxidation by-products of the iodinated X-ray contrast medium (ICM) iomeprol during ozonation in water treatment. Bench-scale investigations revealed that ICM can be partly oxidized during ozonation processes, whereas the ionic Diatrizoic Acid showed the lowest reactivity. Iomeprol, as a representative of ICM, was not fully mineralized during ozonation. Thus, unknown oxidation by-products were formed. Aqueous solutions of iomeprol were treated by ozonation in order to assess the formation of oxidation by-products. The by-products were characterized by different liquid chromatography methods including detection of single-stage mass spectra, product ion mass spectra, and induced in-source fragmentation for analysis of iodine containing oxidation by-products. Aldehyde and carbonyl containing compounds were proposed to be among the stable by-products. A derivatization step confirms that the aldehyde and carbonyl moieties are major functional groups in oxidation by-products of iomeprol. Furthermore, oxidation by-products of iomeprol were detected at the outlet of an ozone reactor at a full-scale waterworks. However, the toxicological relevance of the by-products is a major future research tasks.
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Monitoring of iodinated X-ray contrast media in surface water.
Chemosphere, 2006Co-Authors: Wolfram. Seitz, Jia-qian Jiang, Walter H. Weber, B.j. Lloyd, Matthias Maier, Dietrich Maier, Wolfgang SchulzAbstract:A monitoring programme was carried out in order to determine iodinated X-ray contrast media (ICM) in the River Danube and to investigate the raw water quality for drinking water production at Langenau waterworks. The study revealed that the maximum concentrations of ICM (over 500 ng l−1 for Diatrizoic Acid and iopamidol) were found in 2 h-composite samples taken from the downstream of the Ulm/Neu-Ulm metropolitan area. By means of a concentration profile over one month the highest ICM concentrations were observed on weekdays. The extended data evaluation with principal component analysis shows that the upstream and downstream samples had different pattern of variations in ICM concentration and also demonstrates a clear change in ICM composition by the discharge of municipal wastewater. In addition to load profiles of ICM, time-dependent plots of principal component 1 exhibited peaks, indicating a short-term discharge of ICM between the two sampling sites. In conclusion, a point source for ICM contamination between the sampling sites in Ulm upstream and Leipheim downstream seems to be the reasonable explanation for peak ICM concentrations. Due to the observed high variations of ICM concentrations in river, the evaluation of natural waters by means of a single analysis is not representative.
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Removal of Iodinated X-Ray Contrast Media During Drinking Water Treatment
Environmental Chemistry, 2006Co-Authors: Wolfram. Seitz, Jia-qian Jiang, Walter H. Weber, B.j. Lloyd, Matthias Maier, Dietrich MaierAbstract:Environmental Context.In recent years, many micro-organic pollutants, e.g. pharmaceuticals and personal care products (PPCP), have been observed to be persisting through wastewater treatment and occurring in the environment. Persistent micropollutants are of particular concern owing to the fact that some of them have been found in drinking water, and iodinated X-ray contrast media (ICM) are one group of such pollutants. Abstract.The present study investigates the removal of five iodinated X-ray contrast media (ICM) during drinking water production from surface water at a full-scale water works, which comprises coagulation/flocculation, intermediate ozonation, in-line filtration and adsorption with activated carbon. The elimination rates over all treatment units for the non-ionic ICM (iomeprol, iopromide, iohexol and iopamidol) were determined to be approximately 70%. In particular, intermediate ozonation can remove 30% on average of the non-ionic ICM, whereas it cannot remove the ionic Diatrizoic Acid, and the granulated activated carbon filters can achieve a further 50% removal of non-ionic ICM. However, over 100 ng L−1 of ionic Diatrizoic Acid and 40–100 ng L−1 of non-ionic ICM were found in the produced drinking water.
Katharina Fucke - One of the best experts on this subject based on the ideXlab platform.
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Insights into the crystallisation process from anhydrous, hydrated and solvated crystal forms of Diatrizoic Acid
Chemistry (Weinheim an der Bergstrasse Germany), 2014Co-Authors: Katharina Fucke, Judith A. K. Howard, Garry J. Mcintyre, Marie Helene Lemee-cailleau, C. Wilkinson, Alison J. Edwards, Jonathan W. SteedAbstract:Diatrizoic Acid (DTA), a clinically used X-ray contrast agent, crystallises in two hydrated, three anhydrous and nine solvated solid forms, all of which have been characterised by X-ray crystallography. Single-crystal neutron structures of DTA dihydrate and monosodium DTA tetrahydrate have been determined. All of the solid-state structures have been analysed using partial atomic charges and hardness algorithm (PACHA) calculations. Even though in general all DTA crystal forms reveal similar intermolecular interactions, the overall crystal packing differs considerably from form to form. The water of the dihydrate is encapsulated between a pair of host molecules, which calculations reveal to be an extraordinarily stable motif. DTA presents functionalities that enable hydrogen and halogen bonding, and whilst an extended hydrogen-bonding network is realised in all crystal forms, halogen bonding is not present in the hydrated crystal forms. This is due to the formation of a hydrogen-bonding network based on individual enclosed water squares, which is not amenable to the concomitant formation of halogen bonds. The main interaction in the solvates involves the carboxylic Acid, which corroborates the hypothesis that this strong interaction is the last one to be broken during the crystal desolvation and nucleation process.
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Overcoming the solvation shell during the crystallisation of Diatrizoic Acid from dimethylsulfoxide
Chemical communications (Cambridge England), 2012Co-Authors: Katharina Fucke, Judith A. K. Howard, Jonathan W. SteedAbstract:We present three crystal structures of Diatrizoic Acid (DTA) DMSO solvates illustrating progressive desolvation of the DTA molecule and concomitant increasing degree of DTA self-association. Using these structures, plausible pathways for overcoming the solvation shell of DTA during its crystallisation from solution are discussed.
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A new water... Na+ coordination motif in an unexpected Diatrizoic Acid disodium salt crystal form
Chemical communications (Cambridge England), 2012Co-Authors: Katharina Fucke, Judith A. K. Howard, Michael J. G. Peach, Jonathan W. SteedAbstract:The disodium salt of Diatrizoic Acid crystallises as a tetragonal channel hydrate structure. One of the incorporated water molecules is coordinated to three individual sodium cations in a unique geometry.
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a new water na coordination motif in an unexpected Diatrizoic Acid disodium salt crystal form
Chemical Communications, 2012Co-Authors: Katharina Fucke, Judith A. K. Howard, Michael J. G. Peach, Jonathan W. SteedAbstract:The disodium salt of Diatrizoic Acid crystallises as a tetragonal channel hydrate structure. One of the incorporated water molecules is coordinated to three individual sodium cations in a unique geometry.