Desenvolvimento de método para determinação de BTEX em ar de ambientes internos por DI-CF-SPME-GC/MS

Abstract

Benzene, toluene, ethylbenzene, and xylene isomers (collectively known as BTEX) form an important group of pollutants primarily derived from petroleum products. In indoor environments, BTEX compounds can be emitted from sources such as wood combustion, cigarette smoke, heaters, wood stoves, paints, adhesives, varnishes, and degreasing solvents. Factors like building design and ventilation can also influence their indoor concentrations. In the atmosphere, BTEX compounds contribute to the formation of tropospheric ozone, a pollutant that exacerbates respiratory problems and contributes to global warming. Benzene is classified as a carcinogen, while exposure to the other BTEX components has been linked to cardiovascular, renal, pulmonary, and hematological disorders. The exposure limits recommended by the American Conference of Governmental Industrial Hygienists (ACGIH-USA) for an 8-hour workday are 0.02 ppm for benzene and 20 ppm for toluene, ethylbenzene, and xylenes, respectively. Common methodologies for determining these compounds in air typically employ highly toxic solvents and/or activated charcoal-based adsorbents during the extraction step. In this study, a new method was developed for the determination of BTEX compounds in indoor air using cold fiber direct immersion solid-phase microextraction (CF-DI-SPME), followed by gas chromatography coupled to mass spectrometry (GC/MS). Air sampling was performed actively at a low flow rate using polyurethane foams (PUFs) as adsorbents, packed in three-section cassettes. The extraction of analytes from the foam was carried out by CF-DI-SPME using a polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber. The extraction occurred in an aqueous medium modified by the addition of 50.0 μL of a 1:1 (v/v) acetone/dichloromethane mixture at 55 °C for 15 min under 600 rpm agitation. Determination was performed by GC/MS using a 5% diphenyl–95% polysiloxane column with an initial temperature of 30 °C. Method validation for BTEX determination by DI-CF-SPME-GC/MS followed the Eurachem guidelines. The evaluated figures of merit included linearity, recovery, intermediate precision, repeatability, and limits of detection (LOD) and quantification (LOQ). The linearity study showed homoscedastic calibration curves with coefficients of determination (R²) higher than 0.9. Recoveries ranged from 93% to 106%. Repeatability and intermediate precision were between 3.9%–17.9% and 4.6%– 15.8%, respectively. The LOD and LOQ values ranged from 0.18 μg m⁻³ to 2.97 μg m⁻³ and from 0.61 μg m⁻³ to 9.91 μg m⁻³, respectively. The LOQs obtained for ethylbenzene and xylene isomers were lower than those reported in other studies using HS-SPME-GC/MS for BTEX quantification. Real samples were collected in indoor environments in the municipalities of Betim and Belo Horizonte between January and April 2022. The results complied with the legal limits established. The proposed method is low-cost, presents low detection and quantification limits, and uses minimal solvent volumes. CF-DI-SPME enables miniaturization of the extraction process and shows potential for automation. The method’s scope can be extended to other classes of compounds present in indoor air.