Sequestration of organometallic compounds by natural organic matter. binding of trimethyltin(IV) by fulvic and alginic acids

Sequestration of Alkyltin(IV) compounds in aqueous solution: formation, stability, and empirical relationships for the binding of dimethyltin(IV) cation by N- and O-donor ligands

The sequestering ability of polyamines and aminoacids of biological and environmental relevance (namely, ethylenediamine, putrescine, spermine, a polyallylamine, a branched polyethyleneimine, aspartate, glycinate, lysinate) toward dimethyltin(IV) cation was evaluated. The stability of various dimethyltin(IV) / ligand species was determined in NaCl_aq at t = 25°C and at different ionic strengths (0.1 ≤ I/mol L⁻¹ ≤ 1.0), and the dependence of stability constants on this parameter was modeled by an Extended Debye-Hückel equation and by Specific ion Interaction Theory (SIT) approach. At I = 0.1 mol L⁻¹, for the ML species we have log K = 10.8, 14.2, 12.0, 14.7, 11.9, 7.7, 13.7, and 8.0 for ethylenediamine, putrescine, polyallylamine, spermine, polyethyleneimine, glycinate, lysinate, and aspartate, respectively. The sequestering ability toward dimethyltin(IV) cation was defined by calculating the parameter pL₅₀ (the total ligand concentration, as −log C_L, able to bind 50% of metal cation), able to give an objective representation of this ability. Equations were formulated to model the dependence of pL₅₀ on different variables, such as ionic strength and pH, and other empirical predictive relationships were also found.

Ultraviolet degradation of methyltins: elucidating the mechanism by identification of a detected new intermediary product and investigating the kinetics at various environmental conditions

The photodegradation of methyltins, as environmental pollutants, has scarcely been studied so far because of the shortage of rapid and sensitive speciation methods, even though they have very simple structures. The photodegradation of monomethyltin trichloride (MMT), dimethyltin dichloride (DMT) and trimethyltin chloride (TMT) was studied with our new developed HPLC-FPD hyphenated system, which enables rapid and sensitive detection of methyltins. The half-life times and kinetic rate constants of their degradation at different pH were calculated. The results suggest that MMT, DMT and TMT can be degraded under the UV irradiation rapidly at different pH, with a degradation rate sequence of TMT<DMT<MMT. An unknown intermediary product, which is more stable and has higher concentration at pH 8 for MMT and DMT, of methyltin photodegradation was detected for the first time. This unknown intermediary product was identified as methyloltin with electrospray mass spectrometry, and the possible mechanism was proposed based on the intermediary product. The effects of some environmental parameters such as salinity and humic acid on the degradation rate of methyltins were also investigated. Results suggest that salinity and humic acid have strong effect on their degradation, especially for TMT, which was almost never degraded in the solutions containing NaCl and humic acid.

Speciation of Phytate Ion in Aqueous Solution. Trimethyltin(IV) Interactions in Self Medium

In this paper the results of a potentiometric (ISE-[H+] glass electrode) investigation at t = 25 degreesC on the complexing ability of phytate towards trimethyltin(IV) (tmt) and on the acid-base properties of tmt at high metal concentration (0.050 and 0.075 mol L(-1)) are reported. First we determined the hydrolytic constants of tmt in aqueous solution without further addition of background salt (self medium); in these experimental conditions we verified the formation of the following hydrolytic species: tmt(OH)0, tmt(OH)2(-) and the binuclear species (tmt)2(OH)(+). Successively, we studied the complex formation constants obtained from the interaction of phytate anion with tmt in the same experimental conditions of hydrolytic measurements; the speciation model obtained takes into account several polynuclear species (tmtH5Phy(6-); tmt2H5Phy(5-); tmt3H4Phy(5-); tmt3H5Phy(4-); tmt4H6Phy(2-); tmtsHPhy(6-)). A comparison with literature data is reported too.