Important calibration values to monitor include slope and offset. These numbers provide information on the probe’s overall condition. The offset is the mV reading of the electrode when submerged in pH 7 buffer. Theoretically, the offset is 0 mV; however, the offset shouldn’t exceed ±30 mV. With edge®, the mV reading of the measured pH can be displayed on the LCD. The slope of the electrode is calculated by determining the mV change between two different pH buffers.
Hanna Tip: We recommend that you don't let the offset exceed ±30 mV and the slope percentage stays between 85-105%.
If you have a bad offset, this could mean that you either have a clogged junction or that the probe requires cleaning. If this occurs, try soaking the probe in a cleaning solution and repeat the process of checking offset. If your slope is bad, this could mean you have used expired or contaminated buffers. If this is the case, ensure that fresh buffers are used. edge's Calibration Check probe diagnostics feature will prompt you if there is a problem with your probe.
To learn more about how to calculate your slope and offset, Watch This Video.