A simplified methodology: pH sensing using an in situ fabricated Ir electrode under neutral conditions

Abstract

Herein, a simplified fabrication method for the producing of a pH-sensitive iridium electrode is developed. The in situ electrochemical fabrication of an iridium oxide film is optimized and shown to be achievable under neutral conditions rather than the acidic conditions hitherto employed. The formation of a pH sensitive Ir(III/IV) hydrous film is confirmed via XPS. The amperometric pH-sensing properties of this electrochemically generated material were investigated using square wave voltammetry. In the pH range 2–13, the iridium oxide redox signal has a pH dependency of 86.1 ± 1.1 mV per pH unit for midpoint potentials with uncertainties being ± 0.01–0.05 pH. Finally, the newly developed pH sensor was used to measure the pH of a natural water sample with excellent results as compared to a conventional glass pH probe.

Automatic Microtitrator for Small Volume Samples

“…Sample pH can be accurately measured in small volumes by integrating metal oxide electrodes in microfluidic channels. For example, Steinsberger et al demonstrated a RuO 2 electrode for pH measurements, while Chen et al reported an IrO x electrode . However, while we have used a similar approach in the past with ion selective electrodes, adopting this approach herein would necessitate the use of custom microfluidic cells and would make the instrument setup more complex.…”

“…For example, Steinsberger et al demonstrated a RuO 2 electrode for pH measurements, 23 while Chen et al reported an IrO x electrode. 24 However, while we have used a similar approach in the past with ion selective electrodes, 27 adopting this approach herein would necessitate the use of custom microfluidic cells and would make the instrument setup more complex. The titration process end point determination can be also done spectrometrically using a combination of an LED and a photodiode.…”

“…The pH can easily be measured in situ with potentiometric microelectrodes. For example, Steinsberger et al demonstrated a RuO 2 electrode for pH measurements, while Chen et al reported an IrO x electrode. Nevertheless, many point-of-care systems work with miniscule sample volumes, such as drops of blood.…”

“…The pH can easily be measured in situ with potentiometric microelectrodes. For example, Steinsberger et al 23 demonstrated a RuO 2 electrode for pH measurements, while Chen et al 24 care systems work with miniscule sample volumes, such as drops of blood. While measurement of pH is such small volumes can be done with the aforementioned probes, adjustment of pH in these microvolume samples remains challenging.…”

Advances in sensor developments for cell culture monitoring

“…Several traditional methods have been employed to monitor cell culture, such as the optical microscope, spectrophotometer, chromatograph, electrical sensor, and a mass spectrometer. Recent advancements in analytical methods have supplemented traditional monitoring techniques, relying on an understanding and application of microfabrication, [17][18][19] optical [12,20] and conductive [21,22] materials, sensitive signaling probes, [5] and microfluidic chip packaging. [23,24] This review summarizes the parameters used for monitoring cell culture into four main categories: cellular physiology, cellular environment, cellular metabolite, and contaminant monitoring (Figure 1).…”