Abstract
Soluble inorganic aluminium compounds like aluminium sulfate or aluminium chloride have been challenged by the European Chemical Agency to induce germ cell mutagenicity. Before conducting mutagenicity tests, the hydrolysis products in water and in physiological solutions should be determined as a function of the concentration and pH. We used different 27Al NMR spectroscopic techniques (heteronuclear Overhauser effect spectroscopy (HOESY), exchange spectroscopy (EXSY), diffusion ordered (DOSY)) in this work to gain the information to study the aluminium species in solutions with Al2(SO4)3 concentrations of 50.0, 5.0, and 0.5 g/L and their pH and time dependent transformation. At low pH, three different species were present in all physiological solutions and water: [Al(OH)n(H2O)6 − n](3 − n)+ (n = 0–2), [Al(H2O)5SO4]+, and [Al2(OH)2(H2O)8]4+. Increasing pH reduced the amounts of the two monomer species, with a complete loss at pH 5 for solutions with a concentration of 50.0 g/L and at pH 4 for solutions with a concentration of 5.0 g/L. The dimer species [Al2(OH)2(H2O)8]4+ is present in a pH range between 3 and 6. Less symmetric oligomeric and probably asymmetric aluminium species are formed at pH of 5 and 6. The pH value is the driving force for the formation of aluminium species in all media, whereas the specific medium had only minor effect. No conclusive information could be obtained at pH 7 due to signal loss related to fast quadrupole relaxation of asymmetric aluminium species. A slight reduction of the content of the symmetric aluminium species due to the formation of oligomeric species was observed over a period of 6 weeks. Reference 27Al NMR experiments conducted on saturated water solutions of AlCl3 and those with a concentration of 50 g/L show that the type of salt/counter ion at the same concentration and pH influences the hydrolysis products formed.
Highlights
The REGULATION (EC) No 1907/2006 “REACH” (Registration, Evaluation, and Authorization of Chemicals) [1] dated 18 December 2006 can be considered one of the most complex legislation issued by the European Union [2]
No conclusive information could be obtained at pH 7 due to signal loss related to fast quadrupole relaxation of asymmetric aluminium species
We identified the hydrolysis products of Al2 (SO4 )3 at three different concentrations of 50.0, 5.0, and 0.5 g/L in four physiological media and water, which are routinely used to conduct mutagenicity tests
Summary
The REGULATION (EC) No 1907/2006 “REACH” (Registration, Evaluation, and Authorization of Chemicals) [1] dated 18 December 2006 can be considered one of the most complex legislation issued by the European Union [2]. One of the major purposes of the REACH regulation is to improve and secure a high level of protection of human health and the environment, and to enhance the alternative (non-animal based) test methods to determine the hazards of chemical substances. Information on the toxicity, especially for humans, shall be generated either with methods other than vertebrate animal tests, through qualitative, quantitative structure-activity relationship models, or based on information from structurally related substances wherever possible [3]. If such investigations are performed on inorganic substances, the behavior in water or water-based solutions has to be determined. It is critical to identify the hydrolysis products as a function of the pH and confirm their stability over time in water or water-based solutions
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
