O,O,O-trialkyl phosphorothioates as simple and effective ionophores for silver ion-selective membrane electrodes

O,O,O-tris(2-ethylhexyl) phosphorothioate and O,O,O-tributyl phosphorothioate with a thiophosphoryl (P=S) group are simple and effective ionophores to make Ag+-selective membrane electrodes. The electrode based on O,O,O-tris(2-ethylhexyl) phosphorothioate with bis(1-butylpentyl) adipate (BBPA) as a solvent mediator in a poly(vinyl chloride) membrane matrix exhibited a near-Nernstian response to Ag+ in the concentration range of 5 x 10(-6) to 1 x 10(-2) M with a slope of 56 mV per decade in a solution containing 0.1 M Mg(NO3)(2). The lower limit of detection was 2 x 10(-6) M. This electrode showed high selectivity with respect to alkaline, alkaline earth, and heavy metal ions, except for Hg2+, and could be used over a pH range of 3-8.5. Analogous phosphate esters with a phosphoryl (P=O) group, along with O,O,O-tri-o-tolyl phosphorothioate with a P=S group, were less effective as Ag+ ionophores. (C) 2001 Elsevier Science B.V. All rights reserved.