SCIENTIFIC ANALYSIS LABORATORIES LTD.
Controlled Document pH.html Version 1.5 Last Modified 02/10/11
Method Statement pH
The performance of this method is validated in accordance with internationally recognised procedures.
The measurement of pH is a simple and rapid process yet it provides valuable information. An anomalously low or high pH value in a sample of soil or water indicates the presence of contamination. Furthermore, groundwater of low pH dissolves contaminants more effectively than that of a higher value. Hence, the measurement of pH is important in the field of contaminated land assessment.
The pH is used in conjunction with the sulphate concentration ascertain the optimal chemical composition (type and quantity of cement) for a concrete mix in building developments.
The hydrogen ion activity of a solution is determined from the measurement of the electrochemical potential of a galvanic cell. The cell contains two electrodes, an indicator electrode and the reference electrode. When the electrodes are immersed in a solution, a the potential developed is dependent on both electrodes. Ideal measuring conditions exist when only the potential of the indicator electrode changes in response to varying pH, while the potential of the reference electrode remains constant.
The equipment is calibrated using buffer solutions of known pH.
Log10(Hydrogen ion activity) pH.
Analytical quality control is maintained by a number of measures:
BS:1377: Part 3:1990.
“The Measurement of Electrical Conductivity and the Laboratory Determination of pH Value of Natural, Treated and Waste Waters, 1978”. DOE Methods For The Examination of Waters and Associated Materials, published by HMSO.
APHA & AWWA - Standard Methods of Examination of Waters and Waste Waters 1989 pH value (Electrometric Method).