pH

Measure of solution acidity or alkalinity

pH is the measure of hydrogen ions in a solution. pH is a logarithmic scale ranging from 1 to 14. A solution is considered an Acid below a pH of 7 and alkaline above a pH of 7. PDA Technical Report 29, Points to Consider for Cleaning Validation, warns against using pH as an indication of residual cleaning agents due to the logarithmic nature of the measurement. Instead, conducitivity which directly meassures the ions within a solution should be used to determine residual cleaning agents.