Against the backdrop of rapid industrialization and urbanization, the pollution structure of environmental media such as water bodies, the atmosphere, soil, and sediments continues to evolve. Traditional pollutants and emerging trace pollutants coexist, significantly raising the difficulty and precision requirements of environmental monitoring. Liquid chromatography technology, with its advantages of high separation efficiency, strong anti-interference capability, broad applicability, and the ability to achieve precise quantification of trace substances, can effectively detect thermally unstable, highly polar, and high-molecular-weight organic pollutants, compensating for the shortcomings of traditional detection methods. With the continuous maturation of high-performance liquid chromatography (HPLC), ultra-high-performance liquid chromatography (UHPLC), and chromatographic hyphenated techniques, liquid chromatography has become a core analytical tool in environmental monitoring systems.
I.Working Principles
Liquid chromatography uses a liquid solvent as the mobile phase. Relying on differences in adsorption, partition, ion exchange, and size exclusion of sample components between the stationary phase of the chromatographic column and the mobile phase, it achieves effective separation of complex mixtures. Pretreated environmental samples are driven by a high-pressure pump into the chromatographic column. Different pollutants, due to differences in retention behavior, produce different elution times, achieving orderly separation. The eluted components undergo signal conversion through detectors such as ultraviolet (UV), fluorescence, or mass spectrometry (MS), forming characteristic chromatographic peaks. Combined with the standard curve method, qualitative identification and precise quantification of target pollutants can be accomplished. In view of the complex matrices and low pollutant concentrations in environmental samples, UHPLC and chromatography-mass spectrometry hyphenated techniques have greatly enhanced the analytical capability for trace pollutants.
II.Application Scenarios
1.Water Environment Monitoring
Water environment monitoring is the most mature field for liquid chromatography technology. It can detect organic pollutants in surface water, groundwater, domestic sewage, and industrial wastewater. Pollutants in water bodies such as pesticide residues, phenols, polycyclic aromatic hydrocarbons (PAHs), endocrine-disrupting chemicals (EDCs), and antibiotics are highly toxic and present at low concentrations. Traditional methods lack sufficient quantification precision, whereas liquid chromatography technology can achieve stable and accurate detection. In the control of agricultural non-point source pollution, it can precisely screen pesticide residues and their transformation products. In industrial water environment regulation, it can quantitatively detect characteristic pollutants such as phenols and aromatic hydrocarbons. In addition, liquid chromatography hyphenated techniques can precisely distinguish different toxic forms of heavy metals such as arsenic, mercury, and chromium in water, providing a basis for risk assessment. They can also adapt to the detection of emerging pollutants such as per- and polyfluoroalkyl substances (PFAS) and novel flame retardants.
2.Atmospheric Environment Monitoring
Atmospheric organic pollutants are mostly enriched in PM2.5 fine particulate matter, characterized by low concentrations and complex compositions. UHPLC, with its low detection limits and high separation efficiency, can precisely detect toxic organic compounds such as PAHs and nitrophenols in atmospheric particulate matter, simultaneously completing quantitative analysis of multiple isomers, meeting the needs of regional routine atmospheric monitoring and pollution source tracing. At the same time, this technology can detect aldehydes, ketones, and other organic compounds in industrial exhaust gas under normal temperature conditions, avoiding the decomposition of substances caused by high-temperature detection in gas chromatography, effectively improving detection accuracy.
3.Soil and Sediment Monitoring
Soil and river/lake sediments are important accumulation carriers for pollutants. Persistent organic pollutants such as pesticide residues, PAHs, and PFAS accumulate over the long term, easily causing soil ecological degradation and secondary pollution of groundwater. Using pretreatment methods such as solid-phase extraction (SPE) and accelerated solvent extraction (ASE) combined with liquid chromatography detection technology, efficient extraction and precise quantification of trace organic pollutants in soil and sediments can be achieved. In the safe utilization of agricultural land, contaminated site investigation, and ecological restoration projects, this technology can dynamically monitor changes in pollutant content, providing data support for hierarchical management and control of soil environments.
III.Existing Problems and Optimization Strategies
1.Existing Problems
First, environmental sample matrices are complex, and conventional pretreatment procedures are cumbersome, affecting batch detection efficiency. Second, some emerging pollutants still lack unified national standard detection methods, resulting in poor data comparability. Third, chromatography-mass spectrometry hyphenated equipment has high purchase and maintenance costs, making it difficult to popularize at the grassroots level. Fourth, complex matrix samples are prone to baseline drift, interference from impurity peaks, and other issues, placing high demands on the technical proficiency of operators.
2.Optimization Strategies
First, promote green and efficient pretreatment technologies such as microextraction and online solid-phase extraction to simplify procedures and shorten cycles. Second, accelerate the construction of a standard system for the detection of emerging pollutants, unifying methods and judgment criteria. Third, strengthen training for grassroots technical personnel to reduce human errors. Finally, continuously optimize chromatographic conditions, such as adjusting mobile phase ratios and gradient elution programs, to improve resolution and detection accuracy.
IV.Frequently Asked Questions
Q1：What types of samples are suitable for liquid chromatography analysis?
A1：It is suitable for analyzing organic pollutants with a certain degree of polarity, thermal instability, or large molecular size, including pesticide residues, antibiotics, and endocrine disruptors in water; organophosphorus pesticide residues and persistent organic pollutants in soil; and PAHs and nitrobenzene compounds in atmospheric particulate matter. Highly volatile pollutants are usually analyzed by gas chromatography, and the two techniques complement each other.
Q2：What are the operating environment requirements for a liquid chromatograph?
A2：The temperature should be controlled between 18–28°C, and the humidity should be maintained at 40%–70%. A stabilized power supply and an uninterruptible power supply (UPS) are required. The laboratory should maintain good ventilation and control dust.
Q3：What should be done about peak tailing and baseline drift?
A3：Peak tailing is mostly caused by sample matrix contamination or column aging. Check the mobile phase pH, replace the guard column, or regenerate the analytical column. Common causes of baseline drift include insufficient degassing of the mobile phase, detector lamp energy decay, or temperature fluctuations. These can be investigated and resolved one by one.
V.Conclusion and Outlook
With its excellent separation performance, broad sample applicability, and ultra-high detection sensitivity, liquid chromatography technology comprehensively covers multi-media environmental monitoring scenarios such as water bodies, the atmosphere, soil, and sediments. It is an indispensable core technology in modern ecological environment monitoring systems. In tasks such as quantitative detection of conventional pollutants, screening of emerging pollutants, speciation analysis of heavy metals, pollution source tracing, and ecological risk assessment, liquid chromatography and its hyphenated techniques demonstrate irreplaceable application value.
In the future, as instruments and equipment develop toward intelligence, miniaturization, and high throughput, technologies such as automated pretreatment, intelligent data analysis, and portable on-site detection will gradually become widespread. This will effectively break through the temporal and spatial limitations of traditional laboratory testing and greatly enhance environmental emergency monitoring and routine monitoring capabilities. With the continuous improvement of detection standards and the ongoing optimization of technical systems, liquid chromatography technology will further empower work in fine chemical pollution control, safe utilization of agricultural land, and regional ecological environment governance. It will continuously improve the refinement and scientific level of China's ecological environment monitoring, providing solid technical support for ecological environmental protection and green development.
