RECESSING REDUCES OXYGEN SENSITIVITY OF THE ANTIMONY PH MICROELECTRODE

EMF of antimony pH electrodes is oxygen dependent which degrades its perfo rmance. Oxygen sensitivity of electropl ated antimony pH microelect rodes was experimentally determined for a factorial combination of a) recessing the electrode tip, b)saturating the medium with antimony oxide and c) buffering the medium with phosphate. After establishing the baseline pH sensitivity in phosphate buffers, EMF was measured while the equilibrating gas was varied selectively from 5% to 21% oxygen. Oxygen sensitivi ty of unrecessed microelectrodes was found to be different from that of recessed electrodes. The effects of saturating the medium with antimony oxide and buffering on oxygen sensitivity were found to be not significant. Loss of electroplated antimony from the tip of the electrode was associated with a positive shift in EO'