Needle-like IrO/Ag combined pH microelectrode

In this study, a combined pH microelectrode has been developed consisting of an indicator electrode made of IrO₂ prepared using the polymeric precursor method and deposited in a platinum microwire. This electrode was mounted inside a stainless steel needle, the external surface of which was painted with conductive silver ink which is used as reference electrode. This device was compared with a conventional glass electrode, and the results presented linear behavior in the pH range from 2.0 to 12.5, in Na⁺ and K⁺ solutions, exceeding glass electrodes in the alkaline range. The sensitivity was 56.9 ± 0.2 mV pH^? 1 and using ANOVA test we conclude that the electrode is not sensitive to the presence of alkaline cations such as Li⁺, Na⁺ or K⁺. Finally, the response time (t₉₅) was 4.9 to 9.0 s depending on the solution pH. The combined pH microelectrode can be used several times and, after three years, continues to have a response similar to that of a freshly produced one.