Definition
Pen residual chlorine analyzer is a portable water quality detection instrument, mainly used to quickly determine the concentration of free residual chlorine or total residual chlorine in water samples. Its design is usually pen-shaped, compact and easy to operate and carry in the field. The instrument has a wide range of applications in drinking water treatment, swimming pool management, food processing water monitoring, and industrial circulating water systems.
Principle
The core working principle of the pen residual chlorine analyzer is based on electrochemical or colorimetric methods. In the electrochemical method, the instrument uses a current sensor covered with a membrane, and the residual chlorine molecules selectively penetrate the membrane to undergo redox reaction on the surface of the working electrode, generating a current signal directly proportional to the concentration of residual chlorine, which is directly displayed after circuit amplification and processing. The colorimetric method is based on the color development reaction of DPD (N,N-diethyl-p-phenylenediamine), the residual chlorine in the water sample reacts with the reagent to form a red compound, and the instrument detects the absorbance of the solution through an optical sensor and calculates the concentration according to Lambert-Beale's law. Its basic formula can be expressed as:
A = ε · b · c
where A is the absorbance, ε is the molar absorbance coefficient, b is the length of the optical path, and c is the residual chlorine concentration.
Measurement method
When measuring with a pen residual chlorine analyzer, standardized operating procedures are usually followed. For electrochemical instruments, electrode activation and calibration are carried out first, the sensor is immersed in the water sample to be tested, and the results are recorded after the reading is stable. Colorimetric instruments need to add specific chromogenic reagents to the water sample, mix evenly, put the sample cell into the measuring tank, and the instrument will automatically complete the colorimetric analysis. During the measurement, care should be taken to avoid air bubble interference and ensure that the sample temperature is close to the calibration conditions. Some instruments have temperature compensation to reduce deviations caused by environmental factors.
Influencing factors
The accuracy of the measurement results is influenced by several factors. The pH value of water samples affects the morphology and chemical activity of residual chlorine, and it is generally recommended to measure in the pH range of 6.5-7.5. Temperature changes may change the reaction rate and sensor sensitivity, and compensation and correction should be made according to the instrument instructions. Oxidizing substances present in water, such as ozone, bromide, or manganese ions, can cause cross-interference. In addition, sensor aging, reagent storage conditions, optical path contamination and operator reading errors will also affect the measurement accuracy. Regular instrument validation with standard solutions is an effective measure to ensure data reliability.
Applications
The pen residual chlorine analyzer is suitable for a variety of scenarios where rapid monitoring of residual chlorine concentration is required. In public water systems, disinfectant residues are used to monitor water at the end of the network to ensure safe drinking water. Swimming pools and water parks maintain appropriate disinfection levels through regular testing. The food and beverage industry uses it to monitor the hygiene of production water. Industrial cooling water systems prevent biofouling formation through residual chlorine control. In addition, the instrument can also be used for on-site water quality screening in emergency response and environmental investigations.
Selection considerations
When choosing a pen residual chlorine tester, it is necessary to comprehensively consider the measurement range, accuracy requirements, operating environment and functional requirements. For routine monitoring, a measuring range of 0-5 mg/L is usually sufficient for most applications. In the case where it is necessary to distinguish between free chlorine and bound chlorine, an instrument with corresponding detection mode should be selected. When using it outdoors, pay attention to the protection level and battery life of the instrument. In addition, calibration convenience, data storage capabilities, reagent consumption costs, and compliance with relevant industry standards (e.g., GB/T 5750, ISO 7393, etc.) are also important evaluation factors. It is recommended to evaluate the applicability according to the water quality conditions and operational limitations of actual application scenarios.