Validation of a methodology to determine Benzene, Toluene, Ethylbenzene, and Xylenes concentration present in the air and adsorbed in activated charcoal passive samplers by GC/ FID chromatography

Abstract

This article shows the validation of the analytical procedure which allows determining concentrations of Benzene (B), Toluene (T), Ethylbenzene (E), and Xylenes (X) -compounds known as BTEX- present in the air and adsorbed by over activated charcoal by GC-FID using the (Fluorobenzene) internal standard addition as quantification method. In the process, reference activated charcoal was employed for validation and coconut -base granular charcoal (CGC) for the construction of passive captors used in sample taken in external places or in environmental air. CGC material was selected from its recovering capacity of BTEX, with an average of 89.1% for all analytes. In this research, BTEX presence in air samples, taken in a road of six lines and characterized for having heavy traffic, in Medellín city (Antioquia, Colombia), was analyzed. Samplers employed were located in pairs per point (in 7 transversal strips of the east, central, and west sidewalk), at heights ranging from 2.50 and 3.00 meters, at the floor level, inside a special housing for their protection. The number of total stations was twenty-one (21) in 3 kilometers, with exposition times of 28 days. Analytes desorption procedure was carried out with carbon disulfide as an extraction solvent, and in the chromatograhic analysis of gases this was performed (by triplicate) using a flame ionization detector (FID). An HP-INNOWAX chromatographic column was also used. Ultra-pure Helium, 99.99% purity, was used as carrier gas and in quantification was performed (by triplicate) in the liquid extract in terms of concentration (μg/mL). The research allowed validating the methodology, obtaining recovery percentages ranging between 75.0 % and 98.2 % for all analytes, and quantification limits in μg/mL were 0.279; 0.337; 0.349; 0.391; 0.355; and 0.356 for benzene, toluene, ethylbenzene, p-xylene, m-xylene, and o-xylene, respectively, and it was proven that the validated method was a selective, specific, linear, accurate, and exact method.

Keywords

• validation
• activated charcoal
• volatile organic compounds (VOC’s)
• BTEX
• GC/FID
• BTEX in air