Intramuscular pH needle microelectrode a preliminary report

Abstract

THE GLASS ELECTRODE has been historically the means of measuring interstitial pH. Eisenman and his associates [3] have documented it’s performance characteristics. The disadvantages of the glass electrode are its bulk, fragility, and the distance bet,meen the sensing electrode and the reference electrode. More recently, miniature pH electrodes and microelectrodes have become available 11, 2, 4-61 but most of them require special care. The distance between the sensing surface and the reference surface has been reduced in some of these models, but in most, these surfaces are still too widely separated. A new type of electrode utilizing no glass has been developed and is t,he subject of this report. The pH needle electrode (Fig. 1) is of all-metal construction and is contained within an N-gauge hypodermic ncedlc. Although the needle has been made as short as 2 cm, we have chosen 9 cm as a more convenient size. The ele&rode assembly (Fig. 2) consists of a mercury/mercuric oxide (Hg/HgO) or silver/silver chloride (Ag/AgCl) reference surface and an antimony oxide (Sb,O,) pH sensing surface. The needle electrode is a roncent’ric assembly of the pH sensitive film on a stainless steel subsurface and of the reference surface, which is a silver wire conditioned with either mercury or silver