ESI-MS study of speciation in hydrolyzed aluminum chloride solutions

Abstract

Soluções de AlCl 3 foram analisadas em concentrações de 0,03 a 5,0 mmol dm-3 e pH de 3,5 a 6,0 por espectrometria de massas com ionização por electrospray e analizador quadrupolar (ESI-Q-MS). Esses dados espectrais foram comparados com os obtidos por ressonância magnética nuclear (NMR) de 27 Al e potenciometria. Espécies resultantes da hidrólise do cátion alumínio em solução apresentaram-se principalmente como complexos carregados positivamente (+1) com moléculas de água coordenadas (n = 1-3) ao metal. As análises revelaram que complexos poliméricos de carga +2 e +3 (em concentrações mais elevadas de Al e pH > 4) contêm íons cloretos coordenados. O aspecto geral dos espectros de massas é dependente de parâmetros instrumentais tais como taxa de fluxo de solvente, temperatura na fonte de ionização e voltagens do cone e capilar. Assim, o ajuste fino do instrumento com relação a estes parâmetros foi realizado. Uma tensão de cone de amostra não superior a 50 V levou à melhor correspondência entre dados de potenciometria, ressonância magnética nuclear de 27 Al e espectrometria de massas. Solutions of AlCl 3 were analyzed at concentrations from 0.03 to 5.0 mmol dm-3 and pH from 3.5 to 6.0 using an electrospray ionization quadrupole mass spectrometer (ESI-Q-MS). Mass spectral data were compared with those obtained by 27 Al nuclear magnetic resonance (NMR) spectroscopy and potentiometry. Hydrolytic aluminum species were present in solution mainly as +1 positively charged complexes with n coordinated water molecules (n = 1-3). Analysis revealed that polymeric complexes of +2 and +3 charges (at higher Al concentrations and pH > 4) contained coordinated chloride ions. The general appearance of the mass spectra is dependent on instrumental parameters such as solvent flow rate, ionization source temperature and cone and capillary voltages. Thus, fine tuning of the instrument with respect to these parameters was performed. Sample cone voltages not exceeding 50 V led to the best agreement between potentiometric, 27 Al NMR and mass spectral data.

Theoretical Insight into the Coordination of Cyclic β-d-Glucose to [Al(OH)(aq)]2+ and [Al(OH)2(aq)]1+ Ions

“…It is evident that [Al(OH) 2 (H 2 O) 2 ] 1+ species is the most stable among the five [Al(OH) 2 (H 2 O) n ] 1+ ( n = 0–4) species. This result is in perfect agreement with the recent ESI-Q-MS data, , in which the [Al(OH) 2 (H 2 O) 2 ] 1+ species was strikingly observed ( m / z = 97) in AlCl 3 solution over a pH range of 3.06 to 4.20. , For [Al(OH) 3 (H 2 O) n ] 0 ( m = 3) species, two distinct regions are obviously visible. When n varies from 0 to 1, the Δ G visibly decreases, whereas the Δ G evidently increases with increasing n at high n (≥1).…”

“…17 On the other hand, Tanaka's group reported that the aluminum species existed mainly as [Al(OH) 2 (H 2 O) 2 ] + , [Al(OH) 2 Cl 2 ] − , [Al(OH)Cl 3 ] − , and [AlCl 4 ] − in AlCl 3 solution with a pH of 3.7, using an electrospray ionization quadrupole mass spectrometer (ESI-Q-MS). 18 Đurđevic's group suggested that the hydrolytic aluminum species were present mainly as [Al(OH) 2 (H 2 O)] + and [Al(OH) 2 (H 2 O) 2 ] + in AlCl 3 solution with a pH of 4.20, using ESI-Q-MS. 19 It is obvious that both single-hydroxyl [Al(OH)(H 2 O) 4 ] 2+ and double-hydroxyl [Al(OH) 2 (H 2 O)] + and [Al(OH) 2 (H 2 O) 2 ] + complexes are the crucial aqueous Al III complexes at a pH of around 4.0. Experimental and theoretical studies indicate that the hydrolysis of trivalent aluminum ions is strongly dependent also on possible coordination species in aqueous solution.…”

Improved chemical treatment of Sušica surface water, Zlatibor area, and sludge application

“…Cvijović and Djurdjevic in some papers (Cvijović et al, 2012(Cvijović et al, , pp.1087(Cvijović et al, -1097, (Cvijovic et al, 2012, pp.313-322), (Djurdjevic et al, 2005(Djurdjevic et al, , pp.1615(Djurdjevic et al, -1629 presented the results of studing monomeric species, polymeric species that form during complexation and hydrolysis of Al 3+ ions and amino acids and antibiotics. By varying a degree of neutralization, metal-organic ligand ratio, temperature, pH, the aging time of the Al-solution, mixing speed, different equilibrium species of aluminum and organic molecules are formed and with different yields.…”

Preliminary investigation of aluminium fluoride complexes in aqueous solutions with capillary electrophoresis coupled with electrospray ionization mass spectrometry and with inductively coupled plasma mass spectrometry

“…In aqueous solutions, aluminium ions easily undergo hydrolysis owing to their high affinity to negatively charged hydroxyl groups. Hydrolysis products of aluminium chloride solutions have been extensively studied . Other than hydroxyl and chloride complexes of aluminium, various aluminium fluoride complexes [Al–F complexes] form spontaneously in aqueous solutions at extremely low concentrations of Al and F with high stability constants and are highly toxic .…”

“…Electrospray ionization quadrupole mass spectrometry (ESI‐Q‐MS) has been used for the identification of Al species present at low concentrations in natural water . This technique ensures that the metal ions will be maintained in their “original dissolved form” .…”