title: Study of the effect of sample pressure on in situ BTEX chromatographs.
abstract: In this paper, the influence of sample pressure on benzene measurements obtained with two automated in situ gas chromatographs is studied. The analysers were calibrated using a non-linear regression at 293 ± 1 K and 101.3 ± 0.2 kPa. A gas mixture of benzene in air (5 μg/m3) was produced and measured at calibration conditions. Subsequently, the sample pressure was changed to 80 and 110 kPa. Differences in readings were observed even though the pressure compensators were on, indicating incorrect performance of this tool. Further tests with two different benzene in air mixtures (5 and 40 μg/m3) at 80, 90, 105 and 110 kPa were also carried out. Results showed that the analysers take air from one or several unidentified inlets (apart from the sampling port) when the sampling pressure is lower than the atmospheric one. This is usually the case in air monitoring stations, so this phenomenon is particularly important as systematic biases could be affecting air quality data.
authors.affiliation: Chemical Engineering Department, School of Chemistry, University of Murcia, 30071, Murcia, Spain.
authors.forename: Cristina Romero
authors.initials: CR
authors.lastname: Trigueros
authors.affiliation: Chemical and Environmental Engineering Department, Technical University of Cartagena, Paseo Alfonso XIII, no. 52, 30203, Cartagena, Murcia, Spain. marta.doval@upct.es.
authors.forename: Marta Doval
authors.identifier: http://orcid.org/0000-0001-6142-6396
authors.initials: MD
authors.lastname: Miñarro
authors.affiliation: Chemical Engineering Department, School of Chemistry, University of Murcia, 30071, Murcia, Spain.
authors.forename: Esther González
authors.initials: EG
authors.lastname: Duperón
authors.affiliation: Thermal and Fluid Engineering Department, Technical University of Cartagena, Paseo Alfonso XIII, no. 52, 30203, Cartagena, Murcia, Spain.
authors.forename: Francisco José
authors.initials: FJ
authors.lastname: Marzal
authors.affiliation: Chemical Engineering Department, School of Chemistry, University of Murcia, 30071, Murcia, Spain.
authors.forename: Enrique González
authors.initials: EG
authors.lastname: Ferradás
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D001554:Benzene / Q000032:analysis; D001555:Benzene Derivatives / Q000032:analysis*; D002138:Calibration; D002849:Chromatography, Gas / Q000295:instrumentation / Q000379:methods*; D004784:Environmental Monitoring / Q000295:instrumentation / Q000379:methods*; D008962:Models, Theoretical; D011312:Pressure; D014050:Toluene / Q000032:analysis; D014992:Xylenes / Q000032:analysis
chemical_list: D000393:Air Pollutants; D001555:Benzene Derivatives; D014992:Xylenes; D014050:Toluene; D001554:Benzene; C004912:ethylbenzene
keywords: Air monitoring; Benzene; Chromatography; Data quality; Sample pressure