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

Abstract

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.

Organotin Release from Polyvinyl Chloride Microplastics and Concurrent Photodegradation in Water: Impacts from Salinity, Dissolved Organic Matter, and Light Exposure

“…Under these redox conditions, the surface oxidation of PVC is likely driven by the photochemical production of hydroxyl radicals. OTCs can be photodegraded via dealkylation to produce low-substituted species and finally inorganic tin . Only DMT and DBT were detected in the reaction solutions under different light conditions with an initially increasing and then decreasing trend of concentrations, while the total tin concentrations continuously increased within the experimental period (Figure ).…”

“…OTCs can be photodegraded via dealkylation to produce lowsubstituted species and finally inorganic tin. 35 Only DMT and DBT were detected in the reaction solutions under different light conditions with an initially increasing and then decreasing trend of concentrations, while the total tin concentrations continuously increased within the experimental period (Figure 4). This confirmed that OTCs were concurrently photodegraded as they released from PVC microplastics.…”

Light-Source-Dependent Effects of Main Water Constituents on Photodegradation of Phenicol Antibiotics: Mechanism and Kinetics

“…In previous studies, HA were observed to either accelerate or inhibit the photodegradation of organic chemicals (24)(25)(26)(27). In some cases, the direction of the HA effect is dependent on the irradiation characteristics.…”

Pseudoenzymatic dealkylation of alkyltins by biological dithiols

“…While several papers describe the environmental speciation of alkyltins due to physical and chemical agents [1, 3, 4, 24–32], the data on their interactions with biological targets are rather scarce. A few reports point out the interactions of alkyltin with hemoglobin, H + -ATPase, the xenobiotic efflux pump PDR5, and the ion channel of the F-ATP synthase [33–36].…”