AN IMPROVED POTENTIOMETRIC PCO(2) MICROELECTRODE

The classic Severinghaus pCO(2) microelectrodes have been greatly impr oved, The drift is reduced from similar to 10 to 0.4 mV/h, and the lif etime has been ex-tended from hours or days to one month, The detectio n limit has been lowered to 200 mu atm, and the t(98) for low pCO(2) r esponse is 2 min, Therefore, the microelectrodes can be ex-tended to l ow pCO(2) measurements. In addition, the microelectrodes can be fabric ated more easily. The major problems with the classic pCO(2) microelec trodes are caused bq Pyrex and the reference electrode used for constr ucting the microelectrodes. Pyrex can release chemicals into the inter nal bicarbonate solution and cause serious drift and a short lifetime, Pyrex has been replaced by aluminosilicate glass, and appropriate, Ag /AgCl reference electrodes have been used. The enzyme carbonic anhydra se has been added to the internal bicarbonate solution to accelerate t he hydration reaction, which greatly enhances the response rate and im proves the detection limit. The internal pH glass microelectrodes have been replaced by pH liquid membrane microelectrodes, which makes fabr ication easier and further improves response rate, ?he theory of the e lectrode's response characteristics at low pCO(2) is presented as well as a discussion on the effects of glass materials, the enzyme and pH electrodes.