Analysis of Volatile Organic Components (VOC) in Atmosphere(1)

Significance of the Topic

Monitoring volatile organic compounds in ambient air is essential for protecting public health and ensuring regulatory compliance. Prolonged exposure even at low concentrations can lead to serious effects including cancer. The introduction of air quality standards for substances such as benzene and trichloroethene highlights the need for reliable analysis methods.

Objectives and Study Overview

The primary goal of this work is to describe a solid phase adsorption and thermal desorption gas chromatography mass spectrometry approach for quantifying priority harmful air pollutants. The focus is on sampling over extended periods and achieving trace level detection to meet legal annual average limits.

Methodology and Instrumentation Used

Sampling employs glass or stainless tubes packed with multilayer adsorption media including graphitized carbon black and molecular sieves. Ambient air is drawn at controlled flow rates through a dehydration stage and onto the adsorption tube over 24 hours. Thermal desorption is performed at high temperature to release trapped compounds for GC/MS analysis.

Used Instrumentation

• Thermal desorption unit ATD 400 operating at 280 degrees Celsius with split flow control for primary tube and secondary trap desorption
• Gas chromatograph mass spectrometer GCMS QP5050A equipped with a 60 meter DB 1 capillary column and helium carrier gas

Main Results and Discussion

Example chromatograms demonstrate successful separation and detection of nine priority harmful air pollutants including chloroethene, benzene, trichloroethene and tetrachloroethene at parts per billion levels. Selected ion monitoring yields clear peaks for each target compound. Full scan analysis of laboratory air confirms the capability to identify additional volatiles such as toluene and styrene.

Benefits and Practical Applications of the Method

This combined adsorption desorption GC/MS technique offers high sensitivity, repeatability and the capacity for long duration sampling. It supports environmental monitoring programs, compliance assessment under air pollution laws and early warning of hazardous emissions.

Future Trends and Potential Applications

Advancements may include miniaturized sampling devices, real time thermal desorption integration and automated data processing with machine learning. Expansion to new target compounds and coupling with fast chromatography could further enhance air quality assessment.

Conclusion

The described solid phase adsorption and thermal desorption GC/MS method provides a robust and sensitive approach for atmospheric VOC monitoring. It meets regulatory requirements and delivers reliable data for environmental protection efforts.

References

1. Actual Measuring of Harmful Air Pollutants Editing Committee for Actual Measuring of Harmful Air Pollutants
2. Manual of Measuring of Harmful Air Pollutants Environment Agency Air Quality Bureau Air Regulation Section Edition