Multi-parameter Water Analysis

The application note describes the fully automated potentiometric determination of six significant parameters of water analysis, namely conductivity, pH, total alkalinity, total hardness, chloride and floride content.

Background^:

An adequate supply of good quality water is a fundamental requirement for all industries; whether the water is used for drinking or in manufacturing or cleaning. This makes the measurement of water quality a very essential process. Various parameters affect the quality of the water; the properties that contribute can be physical, chemical or biological factors.

Chemical factors in water analysis involve various parameters such as pH, conductivity, total alkalinity, total hardness, chloride and Fluoride contents etc.

Water hardness is a measure of the amount of calcium and magnesium salts dissolved in water. In Complexometric titration, EDTA reacts with both calcium and magnesium at pH around 10 in the equimolar ratio . As the stability constant of calcium complex is higher than that of magnesium complex, magnesium reacts later. Therefore, for the end point, indicator for magnesium, Eriochrome Black T is used.

Reaction:

Ca²⁺ + EDTA^4- ---------> CaEDTA^2-

Mg²⁺ + EDTA^{4-  -------------->}  MgEDTA^2-

The total Alkalinity of water is sum of all the salts, which react with acid that is HCO₃^-, CO₃^2- and OH^-. Alkalinity is determined by titration of a water sample against standard sulphuric acid solution using colored indicator or pH sensor.

Reaction:

H₂SO₄+2NaOH   -------> Na₂SO₄ +2H₂O

H₂SO₄+2CO₃^2--   -------> 2HCO₃^-+ SO₄^2-

 H₂SO₄+2HCO₃^-   ------> 2CO₂ +2H₂O + SO₄^2-

The given automated titration method can measure multi-parameters in one go. Many water samples can be analyzed with one click of button.

Related Applications:

• Determination of total hardness of water by complexometric titration of calcium and magnesium with EDTA at pH 10 using a Phototrode and Erio T color indicator.
• Determination of the fluoride content by direct measurement with a fluoride ISE