Use of an iridium electrode for direct measurement of pI of proteins after isoelectric focusing in polyacrylamide gel

Electrodeposited Iridium Oxide pH Electrode for Measurement of Extracellular Myocardial Acidosis during Acute Ischemia

“…The AEIROF electrodes showed a near-Nernstian response of -63.5 ( 2.2 mV/pH unit after 2 days of conditioning in tris buffer, pH 7.0. This slightly super-Nernstian behavior is closer to the Nernstian response reported for IrO 2 electrodes prepared by thermal treatment 11,19 or reactive sputtering 18,20,21 Nernstian (70-90 mV/pH unit at 25 °C) response reported for hydrous iridium oxide films prepared by potential cycling. 14,16 The linear response implies that a two-point calibration, as typically made with a glass electrode, would be sufficient.…”

“…[9][10][11][12][13][14][15][16][17][18] Iridium oxide electrodes, in particular, are very attractive candidates because they show (i) potential stability in aqueous solutions over a wide range of temperature and pressure, (ii) a wide pH response range, (iii) a fast response, and (iv) the lowest sensitivity to the redox interference, and (v) they are not sensitive to stirring. 11,13,18 Available literature techniques to construct the IrO 2 pH electrodes include hightemperature oxidation of iridium wetted with NaOH, 11 hightemperature treatment of iridium in molten potassium nitrate, 10 thermal decomposition of an iridium salt, 15,19 anodic activation of Ir substrates in sulfuric acid, 14,16,17 and direct IrO 2 coating by reactive sputtering. 18,20,21 The last approach is advantageous in terms of its sufficient processing flexibility to be compatible with multiple probe microelectrode fabrication, and it is not constrained to the use of expensive iridium substrates.…”

Production and isolation of pH sensing materials by carbonate melt oxidation of iridium and platinum

“…8,9 IrO x has even been used as pH sensitive surface in select ISFET systems in an effort to minimize drift. 10,11 Many methods have been used to produce IrO x electrode materials including reactive sputtering, 12,13 thermal oxidation, [14][15][16][17][18][19][20] and electrochemical methods. [21][22][23][24][25][26][27] However, IrO x produced using these methods resulted in potential drift resulting in errors during continuous pH measurements.…”

pH Determination of APF Gels by an Iridium Electrode (Short Communication)

“…On the other hand, the iridium electrode, which is unattacked by hydrofluoric acid, appears, for the specific field of pH deter mination of APF gels, a particularly con venient alternative to the quinhydrone electrode having a lot of interesting fea tures: it has excellent mechanical proper ties, it can be stored dry over a long period without a shift of its potential, it has low impedance, great compactness and no hysteresis. The advantages of the present electrode over another metal-metal oxide electrode, as the antimony one, were pre viously discussed (Papeschi et al, 1976] and can be summarized with a better accu racy, constant temperature coefficient be tween 0 and 40 °C and insensitiveness to oxygen as well as to stirring. Obviously, the described electrode, which can be obtained in a convenient shape (needle of 0.5 mm diameter or less, protruding 1-2 mm), appears to have a general poten tial usefulness, e.g.…”

“…On the other hand the use of pH-sensitive strips, as reported in a pre vious paper [Caufield and Wannemueh ler, 1984], appears a too approximated procedure. The present paper illustrates the pH measurement of APF gels with a small, reliable, durable and cheap iridium electrode, of the metal/metal oxide type, which was used for determining isoelectric points of proteins [Papeschi et al, 1976] and more recently for in vivo and in vitro proton activity determinations [Papeschi et al, 1981;Bordietal., 1984], Seven different APF gels, packaged in 950-ml plastic bottles, were used (table I). Gels 1-5 were laboratory-prepared within a pH range from 2.1 to 4.6; their composi tion was as follows: 2.72 g sodium fluoride (1.23 g F~); 0.40-4.25 ml 85% phosphoric acid; 0.1 g propyl hydroxybenzoate; 10 g xylitol; 0,14 g saccharin sodium; 1,2 g sodium carboxymethylcellulose (Blanose 7HOF, Hercules); colors (sunset, yellow FCF and Ponceau 4R), mandarin oil and water q.s.…”