The Polarographic Measurement of Halothane

Abstract

The polarographic reduction of halothane on silver cathodes was studied. Silver catalyses the reduction of halothane: two electrons are exchanged in the reduction process. Experiments using a rotating disc electrode showed a linear relationship between observed current and halothane concentration. A Silastic membrane-covered polarographic electrode was constructed using a silver cathode which gave a good linear response to changes in halothane concentration over the range 0.5% v/v halothane in nitrogen. Oxygen interferes with the measurement of halothane, but can be removed from a gas sample before analysis.

Determination of oxygen concentrations by luminescence quenching of a polymer-immobilized transition-metal complex

“…However, Clark electrodes consume oxygen and are easily poisoned by H2S, proteins, and various organic compounds. In operating room use, they register spuriously large oxygen concentrations in the presence of certain anesthetics, which is a potentially fatal shortcoming (3,4). The Winkler titration is slow and cumbersome.…”

Tutorial ReviewElectrochemical analysis of clinicalblood-gases, gases and vapours

“…Most of the studies were conducted at unshielded electrodes, with just two reported with membrane-covered micro-disc electrodes. 104,105 Hence it is possible that the wide variety of results and mechanisms proposed are due solely to the particular experimental conditions encountered when the studies were conducted.…”

“…Albery and coworkers, 104 in 1981, reported on the amperometric reduction of halothane in 1 m KOH solution using a 1.35 mm diameter silver disc rotating-disc electrode and a membrane-covered 50 mm diameter silver micro-disc electrode, with 25 mm silicone film and 75 mm silastic rubber membranes. 104 Measurements were made both in the presence and absence of oxygen, but their results showed that a micro-disc silver cathode electrode covered with a suitable polymer membrane, such as silicone film, might be used to measure halothane concentration in the absence of oxygen, but not in the presence of oxygen. The difficulty was that the half-wave potentials for oxygen and halothane were too close, 20.425 and 20.565 V (versus SCE), respectively.…”

“…Fig. 17 shows the reduction wave for halothane at a silver rotating disc electrode in 1 m KOH solution, taken from the work of Albery et al 104 The halothane reduction effect commences early at approximately 20.3 V versus SCE and the current is transport limited for potentials more negative than 20.7 V. Thus, the halothane wave overlaps that of oxygen (cf., Fig. 5) in addition to that of nitrous oxide (cf., Fig.…”

“…This work suggested that the silver electrode might have a particular affinity for Br. 104 Later studies suggested that gold was a better cathode material to use, 105 since O 2 and halothane displayed clearly separate reduction waves on gold. Unlike on silver, where oxygen reduction appears as a single diffusion-controlled wave, on gold two plateaux of similar magnitude were observed, attributed to two two-electron steps:…”