Should I stir my sample when taking a pH measurement

It is not strictly necessary to stir samples for pH measurement. Although stirring the solution ensures a quicker response, if the buffer solutions are stirred, then the sample should also be stirred. It is important that the stirring is carried out at the same speed for both samples and buffers. By stirring at a uniform rate this ensures a representative sample measurement is obtained (this is particularly important for colloidal or particulate samples) and also improves electrode response time. Electrodes with ceramic diaphragms suffer from interference under stirring. The platinum diaphragm on the other hand does not suffer from this interference and is thus the diaphragm of choice for most common applications.