Why should control standards be used when measuring pH?

For confidence in pH measurement control standards should be run regularly as a check on the functioning of the measurement system. If a control sample is run after calibration and the expected result obtained this will give the user a 99% confidence level in the calibration of the meter, and any results obtained for subsequent sample measurements. In a situation where multiple users are performing pH measurements the use of a control sample will provide confidence in the results being obtained from the different operators. The control buffer selected for use should be within the calibration range of the meter.