[Determination of dissociation exponent of CO2 used in Henderson-Hasselbalch equation by means of bicarbonate-selective microelectrode].
To measure intracellular ion activity of bicarbonate directly, a double-barreled bicarbonate-selective microelectrode was constructed with a liquid ion exchanger(LIX) containing tri-n-octylammonium, trifluoroacetyl-butyl benzene and octanol. A new dissociation exponent of CO2 (pK') was determined experimentally for a modified Henderson-Hasselbalch equation, in which HCO3 activity was used instead of HCO3 concentration. The temperature effects on pK' and solubility coefficient of CO2 were analyzed over the range of 10 to 40 degrees C. The average values of pK' at room temperature (22 degrees C) were 6.377 and 6.348 in water and frog serum, respectively, and the solubility coefficients of CO2 were 0.048 and 0.046 mM/L/mmHg. The values of pK' plotted on Arrhenius plot were shown linear with 1/T, indicating that the pK' thus obtained can be treated thermodynamically as a first-order kinetics. Under normal circumstances, the values for the intracellular pH predicted from the intracellular bicarbonate activities in the proximal tubule and sartorius muscle of bullfrogs were virtually identical with those obtained directly by the LIX-pH-microelectrodes.
D000818:Animals; D001639:Bicarbonates / Q000032:analysis; D002245:Carbon Dioxide / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D008297:Male; D008839:Microelectrodes; D011892:Rana catesbeiana
D001639:Bicarbonates; D002245:Carbon Dioxide