When calibrating a pH meter with standard buffers at pH 4.00, 7.00, and 10.00, what is the primary purpose of performing a multi-point calibration that brackets the expected pH of the samples?

• To clean the electrode bulb of any biological or chemical fouling
• To neutralize any residual acidity in the sample water before measurement
• To determine the actual slope and efficiency of the electrode across the measurement range
• To permanently set the isopotential point of the meter to 0 mV