A Novel Desorption Technique for Improved Sensitivity in Sampling for Gases

Details

• Personal Author:
  Floyd E ; Lungu CT ; Stanishevsky A
• Description:
  Millions of workers are occupationally exposed to volatile organic compounds (VOC) annually, air sampling being the most reliable method to assess their exposure; reducing time to knowledge, while maintaining adequate sensitivity and affordability is a constant struggle. Sorbent sampling is the preferred technique for VOC exposure assessment. Chemical desorption of sorbents is the most common desorption technique, but sensitivity is limited due to small injection fraction. Thermal desorption has excellent sensitivity, but provides only one analysis per sample and is cost prohibitive. We demonstrated a desorption technique that bridges the sensitivity gap between chemical desorption and thermal desorption techniques. We demonstrated that carbonaceous sorbents irradiated with high intensity light can be used to release enough analyte to be directly analyzed by gas chromatography or other analytical methods. Granular Activated Carbon (GAC) is the gold standard for volatile organic compound (VOC) sampling, but recently other carbonaceous porous materials like Single Walled Carbon Nanotubes (SWNT) and porous materials fabricated using Hydrothermal Carbonization (HTC) process have shown comparable adsorption and desorption attributes. Recent studies showed that SWNT efficiently absorb visible light and transform it in heat hinting that irradiation of samples loaded with vapors through air sampling could be desorbed by light irradiation. This will significantly simplify the current analytical methods and will increase sensitivity of analysis. We fabricated several different matrix SWNT substrates based on Chemical Vapor Deposition (CVD), Arc Discharged (AC) and High Pressure Carbon Monoxide (HiPco) synthesis techniques. We also fabricated high surface area carbonaceous spherical particles (CSP) from glucose precursors using Hydrothermal Carbonization (HTC). We characterized their physical and adsorption properties and for some of these substrates we quantified the percentage of analyte released when the loaded substrate was irradiated by various intensities of visible light. For most of the materials we fabricated we demonstrated that they can adsorb significant amount of toluene, used as a reference VOC and when irradiated with visible light a significant percentage of the analyte gets released to be detected by a field grade photo thermal detector (PID). For some of the proposed material configurations we did not succeed yet to produce self-supporting sorbent substrates to be re-used in passive samplers, because of the particular morphology of the materials. However, we were exploring innovative ways to fabricate and test carbonaceous porous materials from inexpensive precursors such as starch, glucose and other naturally occurring materials. We propose that further research to focus in this direction as well as in the making of a prototype sampler using the photothermal desorption technique. [Description provided by NIOSH]
• Subjects:
  Environmental Monitoring Hot Temperature Laboratories Manufacturing And Industrial Facilities Occupational Health Radiation Safety Solvents Temperature Toluene
• Keywords:
  Adsorbents Air-sampling Analytical-instruments Analytical-methods Carbon-compounds Exposure-assessment Gas-chromatography Gas-detectors Gases Heat High-pressure Irradiation Laboratory-techniques Light-absorption Materials-testing Nanotechnology Organic-chemicals Organic-compounds Oxides Porous-materials Samplers Sampling Sampling-methods Sensitivity-testing Surface-properties Thermal-reactions Toluenes Vapors Volatiles

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• Series:
  Grant Final Reports
• Publisher:
  National Institute for Occupational Safety and Health
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Final Grant Report
• Place as Subject:
  Alabama ; Oklahoma ; OSHA Region 4 ; OSHA Region 6
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  OEP - Office of Extramural Programs
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  1-56
• NIOSHTIC Number:
  nn:20047300
• Citation:
  Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, R21-OH-010373, 2015 Nov; :1-56
• Contact Point Address:
  Claudiu T. Lungu, Ph.D., Associate Professor, Department of Environmental Health Sciences, School of Public Health, University of Alabama at Birmingham, 1720 2nd Ave. South, Birmingham, AL 35294
• Email:
  clungu@uab.edu
• CAS Registry Number:
  Carbon monoxide (CAS RN 630-08-0) ; Toluene (CAS RN 108-88-3)
• Federal Fiscal Year:
  2016
• Performing Organization:
  University of Alabama at Birmingham
• Peer Reviewed:
  False
• Start Date:
  20130901
• Source Full Name:
  National Institute for Occupational Safety and Health
• End Date:
  20150831
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:fd3f6a1c3e5e099d0bba3cbbb8c3e50ecb16966ce17a060abeefc85a187248a4db657a7ba7350a31f9662a4b0308f3c6dbc1a824f29d8942c46a0fbe3bc56c6c
• Download URL:
  https://stacks.cdc.gov/view/cdc/218620/cdc_218620_DS1.pdf
• File Type:
  [PDF - 1.80 MB ]