title: Photothermal desorption of single-walled carbon nanotubes and coconut shell-activated carbons using a continuous light source for application in air sampling.
abstract: Many techniques exist to measure airborne volatile organic compounds (VOCs), each with differing advantages; sorbent sampling is compact, versatile, has good sample stability, and is the preferred technique for collecting VOCs for hygienists. Development of a desorption technique that allows multiple analyses per sample (similar to chemical desorption) with enhanced sensitivity (similar to thermal desorption) would be helpful to field hygienists. In this study, activated carbon (AC) and single-walled carbon nanotubes (SWNT) were preloaded with toluene vapor and partially desorbed with light using a common 12-V DC, 50-W incandescent/halogen lamp. A series of experimental chamber configurations were explored starting with a 500-ml chamber under static conditions, then with low ventilation and high ventilation, finally a 75-ml high ventilation chamber was evaluated. When preloaded with toluene and irradiated at the highest lamp setting for 4min, AC desorbed 13.9, 18.5, 23.8, and 45.9% of the loaded VOC mass, in each chamber configuration, respectively; SWNT desorbed 25.2, 24.3, 37.4, and 70.5% of the loaded VOC mass, respectively. SWNT desorption was significantly greater than AC in all test conditions (P = 0.02-<0.0001) demonstrating a substantial difference in sorbent performance. When loaded with 0.435mg toluene and desorbed at the highest lamp setting for 4min in the final chamber design, the mean desorption for AC was 45.8% (39.7, 52.0) and SWNT was 72.6% (68.8, 76.4) (mean represented in terms of 95% confidence interval). All desorption measurements were obtained using a field grade photoionization detector; this demonstrates the potential of using this technique to perform infield prescreening of VOC samples for immediate exposure feedback and in the analytical lab to introduce sample to a gas chromatograph for detailed analysis of the sample.
authors.affiliation: 1.Department of Occupational and Environmental Health, University of Oklahoma Health Sciences Center, 801 N.E. 13th Street, Oklahoma City, OK 73126, USA.
authors.forename: Evan L
authors.initials: EL
authors.lastname: Floyd
authors.affiliation: 2.Departamento de Física, Instituto de Física Aplicada-CONICET, Universidad Nacional de San Luis, Chacabuco 917, CP: 5700, San Luis Capital, San Luis, Argentina.
authors.forename: Karim
authors.initials: K
authors.lastname: Sapag
authors.affiliation: 3.Deep South Center for Occupational Health and Safety, Department of Environmental Health Sciences, University of Alabama at Birmingham, 1665 University Boulevard, Birmingham, AL 35216, USA.
authors.forename: Jonghwa
authors.initials: J
authors.lastname: Oh
authors.affiliation: 3.Deep South Center for Occupational Health and Safety, Department of Environmental Health Sciences, University of Alabama at Birmingham, 1665 University Boulevard, Birmingham, AL 35216, USA clungu@uab.edu.
authors.forename: Claudiu T
authors.initials: CT
authors.lastname: Lungu
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D002244:Carbon; D002606:Charcoal; D002623:Chemistry Techniques, Analytical; D003059:Cocos; D004784:Environmental Monitoring / Q000379:methods*; D006801:Humans; D008027:Light; D037742:Nanotubes, Carbon; D014050:Toluene / Q000032:analysis; D055549:Volatile Organic Compounds / Q000032:analysis*
chemical_list: D000393:Air Pollutants; D037742:Nanotubes, Carbon; D055549:Volatile Organic Compounds; D002606:Charcoal; D014050:Toluene; D002244:Carbon
keywords: VOC; air sampling; bucky paper; exposure assessment; industrial hygiene; photothermal desorption; single-walled carbon nanotubes; toluene