Characterization of a mid-infrared hollow waveguide gas cell for the analysis of carbon monoxide and nitric oxide.
Infrared spectroscopy is commonly applied to the analysis of small gas-phase molecules. One of the limitations of using Fourier transform infrared (FT-IR) spectroscopy for these applications is the time response of long path length gas cells. Hollow waveguides (HW) that transmit in the mid-infrared spectral range have higher optical efficiencies compared to long path length cells due to smaller cell volumes. This study characterizes a silver coated, 2 mm inner diameter HW for the analysis of carbon monoxide (CO) and nitric oxide (NO) and compares the performance to a 3 m gas cell and traditional gas analyzers. The HW was found to have a CO response time less than the NDIR analyzer and approximately one-tenth of the response time on the FT-IR system equipped with a 3 m gas cell. The utility of the increased response time was demonstrated by measuring CO concentrations in sidestream cigarette smoke at the same temporal resolution as an NDIR analyzer. A 10 to 60% increase in sensitivity using various frequencies for both CO and NO was observed using the HW compared to the 3 m multipass gas cell. However, cost savings for gas-sensing applications can be achieved on a per analyte basis by using FT-IR spectroscopy, especially in combination with a HW gas-sensing module, which is significantly less expensive than a multipass gas cell.
Thompson
Bruce T
BT
Brown & Williamson Tobacco Corp., P.O. Box 1056, Macon, Georgia 31202, USA.
Inberg
A
A
Croitoru
N
N
Mizaikoff
Boris
B
D000393:Air Pollutants / Q000032:analysis*; D002248:Carbon Monoxide / Q000032:analysis*; D004784:Environmental Monitoring / Q000379:methods; D009569:Nitric Oxide / Q000032:analysis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D017550:Spectroscopy, Fourier Transform Infrared / Q000295:instrumentation* / Q000379:methods* / Q000706:statistics & numerical data; D014028:Tobacco Smoke Pollution / Q000032:analysis
D000393:Air Pollutants; D014028:Tobacco Smoke Pollution; D009569:Nitric Oxide; D002248:Carbon Monoxide