What Is a Chlorine Analyzer?
A chlorine analyzer is a measuring instrument mainly used to measure residual chlorine.
They are also called Residual Chlorine Analyzers. Products that easily measure chlorine concentration using a color chart may also be included in these products.
Chlorine Analyzers are used in a wide range of situations, such as measuring residual chlorine in tap water and swimming pools.
Uses of Chlorine Analyzers
The range and accuracy of the chlorine concentration to be measured differs for each application. It is important to use a Chlorine Analyzer that can measure the chlorine concentration to be measured with sufficient accuracy.
The main applications of Chlorine Analyzers are as follows:
- To measure whether the residual chlorine concentration in tap water complies with the Water Supply Law
- To control the concentration of water used for washing vegetables, fruits, eggs, etc.
- To measure whether the chlorine concentration in swimming pools complies with hygiene standards
- To measure the chlorine concentration used for sterilization and disinfection in various places, such as industrial equipment and cooling towers, and to control factory water
- To manage sanitation in welfare facilities, kitchens, and food service facilities
- When measuring chlorine concentration as a measure against Legionella bacteria in public bathhouses
- To measure whether the residual chlorine concentration in septic tanks meets the requirements
- For measuring residual chlorine concentration in cooling water returned to the ocean at nuclear power plants and thermal power plants
Principle of Chlorine Analyzers
Chlorine Analyzer principles include the diethyl-paraphenylenediamine method (DPD method), absorbance spectrophotometry, and polarograph (current) method.
1. Diethyl-Paraphenylenediamine Method (Dpd Method)
The diethyl-paraphenylenediamine method (DPD method) is a method to measure chlorine by colorimetric determination using the chemical reaction of DPD. This method is also an official method stipulated by law.
When DPD (diethyl paraphenylenediamine) is oxidized by chlorine, it reacts with unreacted DPD after passing through colorless quinonediimine to produce N, N-diethyl-semiquinone intermediate, which turns pink-red. Based on this principle, it is possible to determine the concentration of residual chlorine by comparing the color concentration in the colorimeter tube with a standard residual chlorine colorimetric series.
DPD reacts immediately with free residual chlorine but reacts slowly with bound residual chlorine. To determine the concentration of total residual chlorine, which is the sum of free and bound residual chlorine, it is necessary to change the bound form to the free form by adding potassium iodide.
2. Absorbance Spectrophotometric Method
The absorbance spectrophotometric method is a mechanical reading method using absorbance spectrophotometry instead of colorimetric determination in the DPD method. It is usually displayed numerically on a digital display or other means.
3. Polarograph (Current) Method
When two electrodes are placed in a sample and voltage is applied, an electric current flows between the electrodes. The amount of current flowing varies depending on the concentration of residual chlorine. The polarograph method measures the chlorine concentration in a sample by measuring the amount of this current.
Chlorine Analyzers for power plants that measure residual chlorine in seawater use the polarograph method and are large. It is also capable of detecting extremely low concentrations in the range of 0 to 100 ppb.
Types of Chlorine Analyzers
Chlorine Analyzers can be classified into colorimetric (DPD), spectrophotometric, and polarographic (current) types, depending on the measurement principle described above, The detailed measurement principle differs depending on the product.
Generally, colorimetric instruments are small and easy to use. Some absorbance spectrophotometric analyzers are also small and portable. Products such as instruments that can measure residual chlorine in tap water and swimming pools without reagents, instruments that can also measure hypochlorite concentration, and instruments that measure high concentrations have their characteristics, and it is necessary to select the right one for the application.
Depending on the measurement range and resolution (measurement performance), there are many products available from various companies, ranging from high-performance/high-priced ones to simple performance/low-priced ones.