# Determination of Eight Benzene Homologs in Ambient Air and Indoor Air in Residential Areas by Secondary Thermal Desorption–Gas Chromatography

## TL;DR

This study developed a new method to accurately measure benzene-related compounds in both outdoor and indoor air using an improved thermal desorption gas chromatography technique.

## Contribution

The novel contribution is an optimized solvent-free secondary thermal desorption–gas chromatography method for reliable detection of benzene homologs in complex air samples.

## Key findings

- The method achieved baseline separation of xylene isomers and showed high linearity (R² > 0.992) with detection limits between 50–120 ng/m³.
- Spiked recoveries ranged from 90.5% to 117.3%, with relative standard deviations between 0.8% and 9.2%, indicating high accuracy and precision.
- Significant correlations were found between indoor and outdoor concentrations of benzene homologs in residential areas.

## Abstract

This study developed and comprehensively validated an optimized analytical method based on secondary thermal desorption–gas chromatography (STD‐GC) for the simultaneous determination of eight key benzene homologs in ambient and indoor air of residential areas. Compared to solvent desorption and single‐stage thermal desorption, STD demonstrates superior desorption efficiency, reduced matrix interference, fully automated rapid operation, complete analyte transfer, thereby eliminating analyte losses while enhancing analytical accuracy and sensitivity, and solvent‐free ensuring friendly to human and the environment. Aiming at the characteristics of target compounds and complex environmental matrices (e.g., humidity, coexisting interferents), sampling parameters, thermal desorption conditions, and gas chromatographic separation conditions were systematically optimized, with particular emphasis on ensuring baseline separation of xylene isomers. The method demonstrated linearity over 10–1000 ng with correlation coefficients (R
2) > 0.992. The spiked recoveries of the method ranged between 90.5% and 117.3%, with relative standard deviations ranging between 0.8% and 9.2%, the detection limits ranged from 50 to 120 ng/m3, and the lower limits of quantitation ranged from 20 to 480 ng/m3. This study established a standardized and highly reliable analytical workflow, addressing the issues of parameter inconsistency and insufficient validation in existing methods when applied to paired residential‐indoor air studies. Using this method, ambient and indoor air samples were synchronously collected and analyzed in residential areas. Results demonstrated significant correlations between indoor and outdoor concentrations of benzene homologs. This study also provides a methodological foundation and practical guidance for accurate assessment of residents’ exposure to benzene homologs.