Dichotomous sampling of vapor and aerosol of methylene-bis- (phenylisocyanate) (MDI) with an annular diffusional denuder.
Am Ind Hyg Assoc J 1994 Aug; 55(8):716-721
An annular diffusional denuder (ADD) was used for dichotomous sampling of vapor and aerosol of methylene-bis-(phenylisocyanate) (101688) (MDI). The ADD took advantage of the large difference in the diffusivities of gases and submicron particles to effect a quantitative separation of the two. The ADD sections and walls were coated with nitro reagent, and the glass fiber filters were dipped in it. Swinney cassettes were used for collecting MDI according to a reference NIOSH technique. ADD samplers were operated at a flow of 10 liters per minute (l/min), and the Swinney cassettes at a flow of 1l/min. Filter samples were desorbed with acetonitrile and sonication for 10min. Samples were analyzed using high performance liquid chromatography. Test atmospheres of MDI ranged from 2.3 to 34.7 parts per billion (ppb). Results showed that the amounts of MDI collected by the ADD correlated quite well with that of the reference sampler over the entire range of MDI concentrations. The ratio of MDI collected by the ADD to that of the reference sampler was 1.4+/-0.09. There was no significant difference between the two samplers according to the paired t-test. The partitioning of MDI into vapor and aerosol was evident in the performance of the ADD sampler. Up to a level of about 75 micrograms/cubic meter (microg/m3), all MDI was found in the denuder section, and beyond this point, breakthrough onto the backup filter was evident, and correlated with aerosol production. While MDI levels in denuders remained fairly constant at 103 to 144.4microg/m3, that on the backup filter continued to rise. The pattern of breakthrough onto the backup filter corresponded to the pattern of aerosol buildup as a function of concentration. The performance of the ADD closely matched theoretical predictions. The authors conclude that the device is efficient and accurate, and that although the MDI aerosol used in testing the apparatus is submicron in size, the ADD can be modified for sampling larger aerosols.
NIOSH-Publication; NIOSH-Grant; Grants-other; Aerosol-sampling; Air-contamination; Air-sampling-equipment; Bronchial-asthma; Environmental-pollution; Occupational-exposure; Pollutants; Respiratory-hypersensitivity
Medicine Tulane University 1700 Perdido St New Orleans, LA 70112
Other Occupational Concerns; Grants-other
American Industrial Hygiene Association Journal
Tulane University of Louisiana, New Orleans, Louisiana