1. Testing standards and methods
Dissolved oxygen, the common detection methods of dissolved oxygen are, electrochemical method, fluorescence method and chemical reagent method (iodometric method).
The electrochemical method, that is, polarographic dissolved oxygen or membrane dissolved oxygen (HJ / 506-2009), is often used to detect natural water, surface water, and some sewage industries. Features, easy operation, easy to carry, low cost of use, and can realize online real-time detection function.
Fluorescence method, a method for measuring dissolved oxygen based on the principle of fluorescence quenching, is widely used. Features, easy operation, easy to carry, but high cost.
The iodometric method, which uses redox reactions to detect dissolved oxygen in water, is the standard method for measuring dissolved oxygen in water. The characteristic is that the cost is low, but the operation is complicated and the requirements are high. The online real-time detection function cannot be realized.
2. pH value detection, the common detection methods are glass electrode method and pH colorimetric method.
The glass electrode method is characterized by high detection accuracy, small interference factors, convenient operation, easy to carry, and can realize online real-time detection function.
Colorimetry. It is mainly based on the principle that certain dyes produce specific color changes with pH changes in the solution. The characteristic is simple operation and low cost, but there are many interference factors, which can not be detected online in real time.
3. Ammonia nitrogen, the detection method used in aquaculture is usually Nessler's reagent method, salicylic acid method or electrode method. The detection accuracy of the Nessler's reagent method and the salicylic acid method is high, and the interference factor is small. If it is online, the cost is high, but the salicylic acid method is greatly affected by the temperature, and the water bath heating should be done below 15 degrees. The electrode method has low precision, high detection limit and high price.
4. Nitrite, the method used for the detection of nitrite is usually spectrophotometry. The nitrite in the water reacts with the reagent to form a red substance. The depth of the red color reflects the level of nitrite content. The higher the deep concentration.
5. Sulfide, the method used for the detection of sulfide is usually the spectrophotometric method. The sulfide in the water reacts with the reagent to form a blue substance. The depth of the blue substance reflects the level of the sulfide. The deeper the blue The higher the concentration.
6. Total hardness. The method used for total hardness testing is usually EDTA titration.
7. Total alkalinity, titration method.