Changes to USP 38 General Chapter 791 pH

Changes to USP 38 <791> pH in USP 39 1S

1.0 The word “Standardization”has been replaced with the word “Calibration”

2.0 The word“read” has been changed with the word “Record”

3.0 The instrument requirements with respect to capability of the system of performing 2-point or more pH calibrations.

4.0 Calibration:

4.1 The value of verification buffer should be between the two buffers used in calibration.

4.2 The acceptance criteria for the calibration revised:

3.2.1. Changed the slope to 90.0% - 105.0% and offset to 0.0 ± 30 mv (0.5 pH units at 25ºC).

3.2.2. Inclusion of instruction to follow supplier instructions for calculating pH sensor slope and offset if using manual method.