Definition
A total nitrogen water quality detector is an analytical instrument used to determine the total nitrogen content in water samples. Total nitrogen refers to the sum of various forms of inorganic nitrogen and organic nitrogen in water bodies, usually expressed as nitrogen concentration, which is one of the key parameters for evaluating the nutrient status and pollution degree of water bodies.
Principle
The instrument works based on the principles of oxidative digestion and photometric detection. First, the nitrogenous compounds in the water sample are converted into nitrates by means of high temperature and high pressure or ultraviolet catalysis. The absorbance properties of nitrate at specific wavelengths are then used to calculate the total nitrogen concentration according to Lambert-Beale's law. Its basic relationship can be expressed as:
A = ε·b·c
where A is the absorbance, ε is the molar absorbance coefficient, b is the path length, and c is the concentration of the DUT.
Measurement method
The mainstream measurement methods include alkaline potassium persulfate digestion-ultraviolet spectrophotometry, high-temperature catalytic oxidation method, etc. The operation process generally covers sample pretreatment, digestion and transformation, color development reaction, optical measurement and data processing. Modern instruments usually realize the integration of automatic digestion and measurement, and meet the requirements of a number of domestic and foreign water quality analysis standards.
Influencing factors
The measurement accuracy is affected by a variety of factors: the turbidity and chromaticity of the water sample may interfere with optical detection; High chloride ion concentration will cause determination bias. The control of digestion temperature and time directly affects the conversion efficiency of nitrogen compounds. Reagent purity and calibration standardization can also have an impact on the reliability of results. It needs to be controlled by blank correction, interference shielding and other measures.
Applications:
This instrument is widely used in environmental monitoring, sewage treatment, industrial production process control, agricultural irrigation water assessment, aquaculture management, laboratory analysis, and other fields. It plays an important role in river and lake water quality monitoring, sewage plant discharge control, industrial circulating water system maintenance and other scenarios.
Key points of selection
When selecting the sample, it is necessary to consider whether the measurement range and detection limit match the characteristics of the sample, whether the analysis speed can meet the requirements of the detection frequency, and whether the instrument has the anti-interference compensation function. At the same time, attention should be paid to the ease of operation, maintenance costs, data output methods and compliance with applicable standards and specifications. For continuous monitoring scenarios, the long-term operation stability and automatic cleaning function of the instrument should be examined.