US Patent 4,900,404
United States Patent and Trademark Office
University of Iowa Research Foundation (Iowa City, IA, US)
An improved phosphate selective membrane electrode using bis(p-chlorobenzyl)tin dichloride as the membrane active component. In addition to this tin compound, the membrane contains N,N-dimethylformamide (DMF), a strong complexing agent for tin compounds.
Arnold, Mark A. and Glazier, Scott A. Phosphate selective membrane electrode. US Patent 4,900,404 filed August 15, 1988 and issued February 13, 1990. https://ir.uiowa.edu/patents/73