I am going to choose an op-amp as a buffer for my pH sensor. How much slew rate of an op-amp is important in choosing my op-amp?
The slew rate of op-amp that I search range from 0.02 V/µs to 12 V/µs.
You only need to worry about slew rate for quickly changing signals, like audio for instance.
pH measurements change so slowly that you can ignore slew rate, and choose the amplifier on power consumption or price.