With the rapid development of industrialization, the problem of oil pollution in water bodies has become increasingly prominent and has become an important factor affecting the ecological environment and human health. Once petroleum substances enter water bodies, they not only damage aquatic ecosystems, but may also accumulate through the food chain, posing potential hazards to humans. Therefore, rapid and accurate detection of oil content in water is a crucial step in fields such as environmental monitoring, sewage treatment, and the petroleum industry. Among numerous oil detection technologies, infrared spectrophotometer has become the mainstream detection equipment in the industry due to its high sensitivity, high selectivity, and easy operation.

1、 Working principle: Quantitative analysis based on feature absorption

The core principle of infrared spectrophotometer is to quantitatively analyze the characteristic absorption characteristics of oil substances in the infrared spectral region. Most petroleum substances (such as alkanes, aromatic hydrocarbons, etc.) exhibit typical C-H bond stretching vibration absorption peaks in the near-infrared and mid infrared bands (typically around 3.4 μ m, or wave numbers of approximately 2930 cm ⁻¹). The intensity of the absorption peak is directly proportional to the concentration of the oil substance.

The specific detection process is as follows: Firstly, collect water samples and extract them using organic solvents such as carbon tetrachloride (CCl ₄) or n-hexane to transfer the oil substances in the water to the organic phase. Subsequently, inject the extraction solution into the sample pool of the infrared spectrophotometer. The infrared light source inside the instrument emits a continuous spectrum, which is separated into specific wavelengths of light by a spectroscopic system (such as a grating or interferometer) and irradiated onto the sample. The detector measures the absorbance of the sample at the characteristic wavelength and calculates the oil content through a built-in algorithm. Modern instruments typically use multi wavelength scanning technology to measure multiple characteristic peaks such as 2930 cm ⁻¹, 2960 cm ⁻¹, and 3030 cm ⁻¹, combined with calibration formulas, which can effectively eliminate interference from other organic compounds and improve measurement accuracy.

2、 Technical features and advantages

1. High sensitivity and wide range: The detection limit of the infrared spectrophotometer can be as low as 0.01 mg/L, which can meet the detection needs of low concentration water samples such as surface water and groundwater. Meanwhile, its measurement range can reach tens of thousands of mg/L, suitable for monitoring high concentration industrial wastewater.

2. Good selectivity and strong anti-interference ability: Compared with UV or weight methods, infrared methods have high selectivity for the characteristic absorption of C-H bonds, which can effectively distinguish oils from other organic compounds (such as surfactants) and reduce false positive results.

3. High degree of automation: It is commonly equipped with automatic sampling, automatic calibration, and data processing functions, significantly improving detection efficiency and reducing human errors. Some models also support integration with the Laboratory Information Management System (LIMS) to achieve seamless data transmission and management.

4. Compliant with standard methods: This technology has been adopted by multiple countries and international standards, such as China's "HJ 637-2018 Water Quality - Determination of Petroleum and Animal and Plant Oils - Infrared Spectrometric Method" and the United States EPA Method 413.2, ensuring the reliability and comparability of test results.

3、 Application areas:

-Environmental monitoring: used for daily monitoring and emergency response of petroleum pollutants in rivers, lakes, oceans and other water bodies.

-Petrochemical industry: Monitor the wastewater discharge of refineries, oil storage facilities, and other facilities to ensure compliance with discharge standards.

-Wastewater treatment: Evaluate the treatment efficiency of wastewater treatment plants and optimize process parameters.

-Oceans and ships: detecting the oil content in ship ballast water and bilge water to prevent marine pollution.

-Research and Education: As important tools for universities and research institutions to conduct environmental science research.

Infrared spectrophotometer, as the "gold standard" technology for oil detection in water, plays an irreplaceable role in environmental protection and industrial production due to its performance. With the continuous advancement of technology, its detection capability will become more accurate, efficient, and environmentally friendly, providing strong technical support for safeguarding water resources security and building ecological civilization.