In general terms, you should choose your calibration solution based on the expected pH of your sample. If you expect the pH of the sample to be 6 pH. Use pH 4.01 and 7.01 calibration solutions. If you expect the pH of the sample to be 8, the use 7.01 and 10.01. Check your manual for more information on this. Some meters have one point calibration or are limited in the calibration solutions that you can use.
