Oxygen solubilities of media used in electrochemical respiration measurements

Solubility data are presented as equations from which the oxygen concentration of arbitrary media may be calculated with an accuracy of about 1%. These equations, covering the range 5-40 degrees C, are based on measurements with a modification of the physical method of St. Helen and Fatt (I. Fatt, Polarographic Oxygen Sensors, CRC Press, Cleveland (1976)). Solutions of the following compounds were measured: EDTA (ethylenediaminetetraacetic acid), EGTA (ethyleneglycol-bis(2-aminoethylether)tetraacetic acid), glucose, Hepes (N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid), lactobionic acid (galactosylgluconic acid), magnesium chloride, mannitol, Mes (2-(N-morpholino)ethanesulfonic acid), potassium chloride, potassium phosphate, sodium chloride, sucrose, taurine, and Tris (tris(hydroxymethyl)aminomethane). The present data are compared with solubility data obtained with the method involving oxidation of calibrated amounts of reduced nicotinamide adenine dinucleotide (e.g., R.W. Estabrook, Methods Enzymol. 10 (1967) 41-47) and with the kinetic method of Reynafarje et al. (Anal. Biochem. 145 (1985) 406-418). It is concluded that the former method produces reliable results provided that some simple precautions are taken. The kinetic method, however, appears to have produced calibration errors up to about 5%.