Indoor Air Monitoring of Volatile Organic Compounds by Thermal Desorption - GCMS

Importance of the Topic

Monitoring volatile organic compounds (VOCs) in indoor air is critical for assessing human exposure to pollutants emitted by paints, cleaning agents and building materials. Chronic VOC exposure can cause respiratory irritation, neurological effects and liver damage. A reliable analytical protocol combining thermal desorption and GC–MS enables both quantitative and qualitative profiling at trace levels.

Study Objectives and Overview

This work describes a method for simultaneous full‐scan (SCAN) and selected ion monitoring (SIM) analysis of 11 target VOCs in indoor air using a Shimadzu TD-30 thermal desorber coupled to a GCMS-QP2020 NX operating in FASST (Fast Automated SCAN/SIM) mode. The study aims to:

• Develop and validate calibration curves down to 2.5 ng per tube.
• Evaluate repeatability and limits of quantitation.
• Compare VOC profiles in four rooms with differing usage and renovation status.

Methodology and Instrumentation

A 66.7 mL/min sampling pump and Tenax TA tubes collected ~4 L of air in one hour. Tubes were thermally desorbed at 250 °C into the cold trap (−25 °C) then transferred to the column (SH-I-624Sil MS, 60 m × 0.32 mm, 1.8 µm). GC conditions: initial 35 °C (5 min), ramp 5 °C/min to 280 °C (5 min). MS conditions: ion source 230 °C, interface 200 °C, scan range m/z 20–600. SIM ions were optimized for each VOC (e.g. chloroform m/z 83, benzene m/z 78). Five‐point calibration (2.5–50 ng) in SCAN/SIM mode validated linearity (R² > 0.99).

Main Results and Discussion

Repeatability (n=5) at 2.5 ng showed RSD < 5% for all targets except toluene (6.1%) and 1,2-dichlorobenzene (5.0%), due to optimized transfer line design minimizing analyte loss. S/N ratios exceeded 47 at the lowest level, establishing 2.5 ng as LOQ. Calibration curves were linear across the range. Four rooms sampled: A (near laboratory), B1 (baseline), B2 (freshly painted), and C (renovated two months prior).

• Room B2 exhibited the highest VOC load, dominated by toluene, xylene isomers and paint additives, confirming post-painting emissions.
• Room A showed elevated early‐eluting solvents (acetone, acetonitrile, hexane, ethyl acetate), likely from adjacent laboratory activities.
• Room C, sampled two months after renovation, had lower VOC levels but still above baseline.
• Room B1 (control) had the lowest concentrations, validating method specificity.

Benefits and Practical Applications

The combined SCAN/SIM approach with FASST provides:

• Low‐level quantitation (ppbv) of targeted VOCs using SIM.
• Broad screening capability for unknowns via SCAN data.
• High throughput for indoor air quality surveys, occupational monitoring and building assessment.

Future Trends and Opportunities

Advances may include integration of multi‐bed sorbents for extended VOC ranges, real‐time desorption units for field deployment, and AI‐driven deconvolution of complex SCAN spectra. Coupling with compact GC–MS or ion mobility spectrometry could facilitate on-site monitoring. Standardization efforts will expand analyte lists and strengthen data comparability.

Conclusion

The TD-30/GCMS-QP2020 NX method in FASST mode achieves robust, sensitive quantitation of indoor VOCs while retaining untargeted screening capability. Repeatability, LOQ and calibration performance meet ISO 16000-6 requirements. Application to four distinct rooms demonstrates its power to distinguish emission sources and assess renovation impacts.

Reference

1. EPA. Introduction to Indoor Air Quality.
2. ISO 16000-6:2011 Determination of VOCs in Indoor Air.
3. US EPA TO-17: VOC Determination by Sorbent Tubes.
4. Kozicki et al. Emission of VOCs from Cementitious Sealants. Sustainability. 10, 2178 (2018).