Abstract: A microsample pH meter was prepared by modifying Iridium oxide thin film on a microelectrode using an electrochemical method. In the measurement process, the potential difference between the test and reference electrode was determined by dropping only approximately 3~5 μL solution on the electrode which with small volume. Then, data was obtained using a data acquisition card. The potential difference signal is converted into a digital signal, and the pH value is output with the Matlab software fitting curve. The measurement results of microsample pH meter are consistent with those of commercial pH meters. The electrode is convenient,and high sensitivity and good reproducibility, and it has superiority in the analysis of rare and expensive samples biological samples. Therefore, it has broad development prospects.

Key words: pH meter, micro sample, iridium oxide electrode, potential difference, miniaturization