E-mail: michael@shboqu.com   |   Expert in Water Quality Measurement and Water Treatment Project

How to choose the measurement method of the multi-parameter water quality analyzer according to the needs?

by:BOQU     2021-05-18


In order to protect the water environment, it is necessary to strengthen the monitoring of sewage discharge. The planning of testing points and the quality of testing instruments (primarily multi-parameter water quality analyzers) play a vital role in water environment monitoring. Use chemical and physical methods to determine the content of various chemical components in the water. Multi-parameter water quality analyzers are divided into three types: simple analysis, full analysis, and special analysis.

The simple analysis is carried out in the field, with few analysis items, but it requires quick and timely analysis. It is suitable for starting to understand the primary chemical composition of groundwater in various aquifers in a large area. The project is determined according to the needs of specific tasks. Another multi-parameter water quality analyzer can quickly and accurately qualitative and quantitative analysis, and can be fully active, intelligent, real-time online, multi-parameter simultaneous analysis, at the same time the results and print the report.

So how do we choose the measurement method according to our needs?

1. Fast digestion method

The classic standard method is the 2h reflow method. Various fast analysis methods are proposed to improve the speed of analysis. There are two main methods:

One is to improve the oxidant concentration, sulfuric acid acidity, reaction temperature, and other conditions in the digestion reaction system to increase the reaction speed. Our multi-parameter water quality analyzer manufacturers recommend the 'Coulometric method' and 'Quick-off catalytic digestion method (including photometric method)' as representative.

The national standard for ammonia nitrogen analyzer: the salicylic acid colorimetric method completes the determination of ammonia nitrogen in the water, and the international standard rule of sodium dichloro isocyanate is used to replace the general sodium hypochlorite so that the stability of chlorine and the effectiveness of the reagent solution are greatly improved. Enhanced (Type B) Because of the various types of microwave ovens and different powers, it is difficult to test uniform power and timing to achieve outstanding digestion.

2. Spectrophotometry

According to the classic standard method, potassium dichromate oxidizes organic matter and hexavalent chromium generates trivalent chromium. After establishing the relationship between the absorbance value of hexavalent chromium or trivalent chromium and the COD value of the water sample, confirm the COD value of the water sample. Using the above-mentioned principle (YunL_uuu), the most representative method abroad is EPA. Method 0410.4 active manual colorimetry, ASTM: D1252-2000 water chemical oxygen demand measurement method B sealed digestion spectrophotometry and international standard ISO15705-2002 water. The chemical oxygen demand (COD) was measured by the small sealed tube method.

3. Regulations for Potassium Dichromate

The COD is measured through the potassium dichromate standard method to obtain an accurate COD value, but the COD potassium dichromate standard method has many defects. The standard operation of the COD potassium dichromate standard method is complicated, and heating and refluxing take a long time, and the equipment used for heating and refluxing is large in size and difficult to measure in batches.

4. Potassium permanganate method

Same as the potassium permanganate (potassium) method, potassium permanganate (KMN) is used as an oxidant to determine COD, that is, potassium permanganate index (CODMN). According to different experimental specifications, there are two types of ammonia nitrogen analyzers: Type A and Type B. In the meantime, Type A uses Nessler’s reagent colorimetric method GB7479-87, the national standard GB7148-81, and the international standard ISO7150/1-1948 standardized salicylic acid photometric method as the basic experimental method, supplemented by the sample colorimetric reaction pretreatment. Reach the purpose of RAP. The ID of the sample and accurate colorimetric determination have the advantages of stability, sensitivity, reliability, and no mercury. (The potassium permanganate method is suitable for the detection of low COD content.

5. Rapid digestion spectrophotometry

The chemical oxygen demand (COD) evaluation method is either the reflux method, rapid method, or photometric method. Chromite (potassium) is used as oxidant, sulfur (chemical symbol: S) acid (chemical formula: H2SO4) silver is As a catalyst, mercury sulfate is a masking agent for chloride ions, and it uses a COD digestion system based on the acidic conditions of sulfuric acid.


6. COD analyzer (analyzer) UV meter measurement method

The UV measurement method of chemical oxygen demand is also an emerging measurement method. It has the advantages of accurate measurement and low capital cost (that is, the accumulation of future benefits). COD tester is a new product developed with new electromechanical technology. With the application of cold light display technology, the service life of the light source lamp can reach 100,000 hours. The optical switch for measuring parameters is automatically converted from manual to active, which eliminates the error factor of artificial rotation.

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