Spectroscopy is based on the interaction between matter and electromagnetic waves, and detection is achieved by measuring absorption, emission, or scattering spectra. For example, UV visible spectroscopy uses the absorption peaks of organic compounds in specific bands for quantitative analysis, while fluorescence spectroscopy calculates pollutant concentrations based on the fluorescence intensity emitted by excited state molecules. Its advantages include no need for chemical reagents, no secondary pollution, real-time monitoring of multiple parameters, and low equipment maintenance costs. However, a single spectral method is susceptible to matrix effects, such as nitrate and organic matter in water that may mask the target signal, resulting in insufficient model generalization ability. Therefore, it is necessary to combine chemometric algorithms to improve accuracy.

Electrochemical methods rely on the oxidation-reduction reactions occurring on the electrode surface to reflect the concentration of pollutants through changes in current or voltage. Taking COD detection as an example, the current generated when organic matter is oxidized on the electrode is proportional to its content, and it has the characteristics of high sensitivity, fast response speed (in seconds), and supports online continuous monitoring. However, electrodes are easily affected by water quality, such as pH value and metal ions that may interfere with the reaction, and require regular calibration; After long-term use, the electrode surface is prone to contamination, maintenance costs are high, and it is difficult to simultaneously detect multiple parameters.

Chromatography achieves substance separation through the distribution difference between the stationary phase and the mobile phase, and combines with a detector to complete quantitative analysis. Gas chromatography is good at detecting volatile organic compounds, while liquid chromatography is suitable for pollutants with high molecular weight and poor thermal stability, such as pesticides and phenols. Its separation efficiency is high and the detection sensitivity can reach the Danak level, but the equipment is complex, the cost is high, and it requires professional personnel to operate. It usually needs to be combined with mass spectrometry to enhance qualitative ability.

Comprehensive comparison: Spectral method is suitable for rapid screening and real-time monitoring, but its accuracy is limited by the model; Electrochemical method has advantages in sensitivity and response speed, but lacks stability and multi parameter detection capability; The accuracy and separation ability of chromatography are outstanding, but the cost and operational threshold are relatively high. In practical applications, it is often combined according to the needs of the scenario, such as using spectroscopy for online warning and chromatography for laboratory confirmation, in order to balance efficiency and accuracy.