Chlorine disinfectant is a commonly used disinfectant and is widely used in the disinfection process of tap water, swimming pools, tableware, etc. However, chlorine-containing disinfectants will produce a variety of by-products during disinfection, so the safety of water quality after chlorination disinfection has attracted increasing attention. Residual chlorine content is an important indicator for evaluating the effectiveness of water disinfection.
In order to inhibit the repopulation of residual bacteria, viruses and other microorganisms in the water, after the water has been disinfected with chlorine-containing disinfectants for a period of time, there should be an appropriate amount of residual chlorine in the water to ensure continued sterilization ability. However, when the residual chlorine content is too high, it can easily cause secondary pollution of water quality, often lead to the production of carcinogens, cause hemolytic anemia, etc., which has certain harmful effects on human health. Therefore, effectively controlling and detecting residual chlorine content is crucial in water supply treatment.
Several forms of chlorine exist in water:
Residual chlorine (free chlorine): Chlorine in the form of hypochlorous acid, hypochlorite, or dissolved elemental chlorine.
Combined chlorine: Chlorine in the form of chloramines and organochloramines.
Total chlorine: Chlorine present in the form of free residual chlorine or combined chlorine or both.
For the determination of residual chlorine and total chlorine in water, the o-toluidine method and the iodine method were widely used in the past. These methods are cumbersome to operate and have long analysis cycles (requiring professional technicians), and cannot meet the requirements for rapid and on-demand testing of water quality. requirements and are not suitable for on-site analysis; moreover, because the o-toluidine reagent is carcinogenic, the residual chlorine detection method in the “Hygienic Standards for Drinking Water” promulgated by the Ministry of Health of the People’s Republic of China in June 2001 has removed the o-toluidine reagent. The benzidine method was replaced by DPD spectrophotometry.
The DPD method is currently one of the most accurate methods for instant detection of residual chlorine. Compared with the OTO method for detecting residual chlorine, its accuracy is higher.
DPD differential photometric detection Photometry is an analytical chemistry method usually used to measure the concentration of low-concentration chlorine residual or total chlorine in water samples. This method determines chlorine concentration by measuring the color produced by a certain chemical reaction.
The basic principles of DPD photometry are as follows:
1. Reaction: In water samples, residual chlorine or total chlorine reacts with specific chemical reagents (DPD reagents). This reaction causes the color of the solution to change.
2. Color change: The compound formed by DPD reagent and chlorine will change the color of the water sample solution from colorless or light yellow to red or purple. This color change is within the visible spectrum range.
3. Photometric measurement: Use a spectrophotometer or photometer to measure the absorbance or transmittance of a solution. This measurement is usually performed at a specific wavelength (usually 520nm or other specific wavelength).
4. Analysis and calculation: Based on the measured absorbance or transmittance value, use the standard curve or concentration formula to determine the concentration of chlorine in the water sample.
DPD photometry is usually widely used in the field of water treatment, especially in testing drinking water, swimming pool water quality and industrial water treatment processes. It is a relatively simple and accurate method that can quickly measure the concentration of chlorine to ensure that the chlorine concentration in the water is within the appropriate range to eliminate bacteria and other harmful microorganisms.
Please note that specific analytical methods and instruments may vary between manufacturers and laboratories, so when using DPD photometry, please refer to the specific analytical method and instrument operating manual to ensure accuracy and repeatability.
The LH-P3CLO currently provided by Lianhua is a portable residual chlorine meter that complies with the DPD photometric method.
Compliant with industry standard: HJ586-2010 Water Quality – Determination of Free Chlorine and Total Chlorine – N, N-diethyl-1,4-phenylenediamine spectrophotometric method.
Standard testing methods for drinking water – Disinfectant indicators (GB/T5750,11-2006)
Features
1, Simple and practical, efficient in meeting needs, quick detection of various indicator and simple operation.
2, 3.5-inch color screen, clear and beautiful interface, dial style user interface, concentration is direct-reading.
3, Three measurable indicators, supporting residual chlorine, total residual chlorine, and chlorine dioxide indicator detection.
4, 15 pcs of built-in curves, supporting curve calibration, meeting the requirement of scientific research institutions, and adapting to various testing environment.
5, Supporting optical calibration, ensuring luminous intensity, improving instrument accuracy and stability, and extending service life.
6, Built in measurement upper limit, intuitive display of exceeding limit, dial displaying detection upper limit value, red prompt for exceeding limit.
Post time: May-24-2024
