Accuracy and precision in vitro of Beetrode microelectrodes used for intraoral pH measurements

The accuracy and precision of 12 different microelectrodes were assessed through a series of pH recordings of buffer solutions with known pH values. Some electrodes were quite accurate, yielding an average deviation of recordings from true values of about 0.05 pH units, while other electrodes yielded average deviations of up to 0.20 pH units. The precision of the electrodes also varied between electrodes. While all recordings were within 0.15 pH units from the true values for some electrodes, other electrodes showed a marked dispersion with less than 25% of the recordings being within 0.15 pH units from true values. For some electrodes accuracy depended on true pH values, while no such dependency was noted with respect to the precision of the electrodes tested. Both accuracy and precision may be impaired when pH recordings are made on solutions with pH values outside the pH range encompassed by the calibration buffers. Our results demonstrate that the accuracy and precision of these microelectrodes cannot be considered fixed and known parameters. Electrodes should therefore be checked prior to clinical use, and electrodes with low accuracy and precision should be excluded from further use.