Improvement of a Phosphate Ion-selective Microsensor Using Bis(dibromophenylstannyl)methane as a Carrier

An ionophore-doped sensing membrane phosphate (PO₄) microsensor based on bis(dibromophenylstannyl)methane (Bis microsensor) is described. The Bis microsensor showed a Nernstian response. The response of the Bis microsensor was log-linear down to a monohydrogen phosphate ion (HPO₄^2-) concentration of 0.5 μM (corresponding to 1.0 μM of orthophosphate at pH 7.2), whereas the detection limit of PO₄-microsensors based on trialkyl/aryltin chloride was 50 μM of HPO₄^2-. The Bis microsensor showed excellent selectivity for HPO₄^2- against nitrite, nitrate, chloride, bicarbonate and sulfate, as compared with PO₄ microsensors based on trialkyl/aryltin chloride. Dissolved oxygen, which is known to interfere with the response of a previously developed cobalt-based potentiometric solid-state PO₄ microsensor, had no effect on the response of the ionophore-doped sensing membrane-type microsensors described herein. Only OH^- (i.e., pH) interfered with the ionophore-doped sensing membrane-type microsensors.