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The Use of Concentrated NaN0 3 in tcP o2 Electrodes to Diminish O 2 Consumption and Dehydration Drift
Author(s) -
Thunstrom A. M.,
Severinghaus J. W.
Publication year - 1978
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/j.1399-6576.1978.tb01393.x
Subject(s) - cellophane , electrolyte , electrode , cathode , membrane , analytical chemistry (journal) , polypropylene , solubility , deposition (geology) , materials science , chromatography , composite material , chemistry , organic chemistry , paleontology , biochemistry , sediment , biology
We investigated: (1) The effects of NaN0 3 concentration, membrane material and thickness, and electrolyte layer thickness on electrode O 2 consumption, stirring effect (Ø) and response time; (2) The effect of NaNO 3 on P(H 2 0) and electrode drift; and (3) The effect of KCl on Ag deposition at the cathode. Electrolytes containing 0–8 m NaN0 3 , 0.01 m KCl, and 0.1 m pH 7 phosphate were tested in a 20 μ cathode tcP o2 electrode at 42d̀C. Increasing NaNO 3 concentration reduced O 2 solubility and sensitivity by a factor: e ‐(C/4.6). Thus, sensitivity was a linear function of solubility. Without cellophane, sensitivity with 12 μm polypropylene was 50% that of 25 μm Teflon; 7 m NaNO 3 reduced sensitivity for both membranes by about 60%. 12 μ cellophane, by increasing the thickness of the electrolyte layer, minimized the difference between the membranes and exaggerated the effects of increasing NaNO 3 concentration on sensitivity. Ø was a linear function of sensitivity. Cellophane decreased the ratio of Ø to sensitivity. Response times of electrodes were almost unaffected by addition of NaNO 3 , but were increased as expected by use of thicker membranes, and by addition of cellophane spacers. Electrolyte vapour pressure was decreased 67% by addition of 7 m NaNO 3. When electrolyte vapour pressure differed significantly from that of skin or calibration solutions, water crossed the polypropylene or Teflon membranes, changing the O 2 sensitivity, and causing drift both on skin and in calibration solutions. With KCl containing electrolytes, silver deposition occurs at the cathode, the rate of deposition increasing greatly as KCl concentration approaches saturation. Thus addition of NaNCO 3 to O 2 electrolytes lowers vapour pressure, delays dehydration, reduces O 2 sensitivity by reducing permeability of the electrolyte layer to O 2 , and thereby reduces the gas/skin correction factor Ø, without significantly delaying response time, and without increasing silver deposition.