Reducing blank values for trace analysis of ionic organotin compounds and their adsorption to different materials

Abstract

Organotin compounds (OTC) are highly toxic pollutants strongly affecting many ecosystems. As analytical techniques for OTC have improved in the past, problems with blank values and adsorption to container walls have been revealed. In this study, OTC adsorption to different materials was studied, and different methods such as derivatization, complexation, extraction, UV-light treatment, nitric acid baths, glowing at high temperatures, and rinsing with detergents and distilled water were tested to reduce OTC blank values from chemicals, solutions, and containers of different materials. Rinsing with detergents and distilled water was effective for decontaminating containers of different materials. Glowing at high temperatures was specifically suitable for glassware and chemicals with high melting points. UV-light treatment was suitable only for solutions. However, OTC underwent disproportionation, and tin became methylated under high temperatures and UV-light treatment. Methods combining sodium tetraethylborate and organic solvent extraction had the best decontamination effects among all methods but were not economical. Sodium borohydride provided another alternative but was less effective. However, use of sodium tetraethylborate and sodium borohydride was restricted to aqueous solution and in certain pH ranges. No material was found without adsorption of all OTC in this study. Tributyltin and dibutyltin adsorbed strongly in the Teflons, polyethylene, and silanized glass. Monomethyltin and monobutyltin had strong adsorption in most materials. Different materials should be used for different OTC in adsorption studies. The use of extraction reagents to recover OTC from container walls is suggested to avoid underestimation of OTC concentrations in waters.