Non-obvious Problems in Clark Electrode Application at Elevated Temperature and Ways of Their Elimination

Abstract

Well-known cause of frequent failures of closed oxygen sensors is the appearance of gas bubbles in the electrolyte. The problem is traditionally associated with insufficient sealing of the sensor that is not always true. Study of a typical temperature regime of measurement system based on Clark sensor showed that spontaneous release of the gas phase is a natural effect caused by periodic warming of the sensor to a temperature of the test liquid. The warming of the sensor together with the incubation medium causes oversaturation of electrolyte by dissolved gases and the allocation of gas bubbles. The lower rate of sensor heating in comparison with the medium reduces but does not eliminate the manifestation of this effect. It is experimentally established, that with each cycle of heating of measuring system up to 37°C followed by cooling the volume of gas phase in the electrolyte (KCl; 60 g/L; 400 μL) increased by 0.6 μL approximately. Thus, during just several cycles it can dramatically degrade the characteristics of the sensor. A method was developed in which the oxygen sensor is heated in contact with the liquid, (depleted of dissolved gases), allowing complete exclusion of the above-mentioned effect.

Direct Measurements of Oxygen Gradients in Spheroid Culture System Using Electron Parametric Resonance Oximetry

“…micro-electrodes) suffer from several inherent limitations leading to unreliable results (oxygen production/consumption by electrode, signal drift, media requirements etc. [ 23 ]). Electron paramagnetic resonance (EPR) oximetry is widely accepted as one of the most reliable techniques with which to measure free radicals and oxygen in tissues [ 32 ].…”

“…Alternatively, mathematical modelling of spheroid micro-environments is feasible with some basic information of the spheroid obtained destructively through histochemical staining of spheroid sections [ 22 ]. It should be noted that there is little consensus in the literature on the most appropriate method to use due to recently documented difficulties/limitations of these methods [ 23 ].…”

ROS in Platelet Biology: Functional Aspects and Methodological Insights

“…These parameters can be determined in platelets using a Clark oxygen electrode. This method has been used with isolated mitochondria and platelets but showed several problems including uniform signal drift, low sensitivity, changes in sensor response, and bubble formation on the electrode [ 197 ]. Recently, cell permeable fluorescent probes have been developed; some of them are based on probe quenching by O2 resulting in a reduction in fluorescence or in O2-dependent red shift of fluorescence [ 198 ].…”

Rapid kinetics of changes in oxygen consumption rate in thrombin-stimulated platelets measured by high-resolution respirometry

“…Pioneering experiments starting in the 1970s using Clark-type oxygen electrodes showed that platelet activation with a range of physiological stimuli triggers a rapid increase in O 2 consumption, attributed to increased mitochondrial OXPHOS (inhibited by oligomycin) and oxidation of arachidonic acid by cyclooxygenase (COX; inhibited by aspirin) [ 6 , 7 ]. However, Clark-type electrodes show a number of problems, including uniform signal drift, changes in sensor response, and bubble formation on the electrode [ 8 ]. Importantly, the resolution achievable with Clark-type electrodes is relatively low compared to high-resolution approaches currently available.…”