Page:NIOSH Manual of Analytical Methods - 2550.pdf/4

 BENZOTHIAZOLE IN ASPHALT FUME: METHOD 2550, Issue 1, dated 15 January 1998 - Page 4 of 5 This method has been used to analyze field generated air samples from several NIOSH asphalt paving studies (Figure 1). It was not evaluated with laboratory generated air samples. All of the desorption efficiency, recovery and storage studies have been performed with laboratory spiked sorbent tubes. Sampling was done with ORBO-42 Large sampling tubes, because the 10-mm OD allowed for a reduced pressure drop, which enabled 8-h samples to be collected at 2 L/min. Benzothiazole in the vapor state is adsorbed on the washed XAD-2 of the ORBO-42 Large sampling tube. However, samples taken during field ® studies where high particulate matter was present have shown some benzothiazole on the Teflon prefilters. This is most likely caused by the entrapment or adsorption of the benzothiazole on the particulate matter. Spiking studies of fresh Teflon filters have shown that benzothiazole is not retained by the filter. It is, therefore, suggested that in those sampling circumstances where particulate matter will be encountered during the sampling process that a Teflon pre-filter be used and analyzed in the same manner as the sampling tube media beds. The quantity of benzothiazole determined on the filter can then be added to the quantity found on the sampling tube to give a total benzothiazole mass for the sample. Because of the larger diameter of the ORBO-42 Large sampling tube, the front sorbent bed is not always uniform in depth, thus making laboratory spiking of the sampling tubes difficult and recoveries variable. For this reason, ORBO-43 tubes, which contain the same amount of XAD-2 resin, but have a smaller tube diameter (8-mm OD) and a more uniform resin bed, were utilized to determine extraction efficiency, recovery, and storage stability of benzothiazole. Extraction efficiency of the benzothiazole from the ORBO43 sorbent tubes is typically 89 to 96% (Figure 2). A thirty day storage study at 4C for 20-µg samples showed a recovery of 89.1% based on day 1 data [1]. This falls slightly below the NIOSH stability criterion of 90% recovery.

REFERENCES: [1] [2]

Jaycox LB [1997]. Backup Data Report for Method 2550, Benzothiazole in asphalt fume, (unpublished), NIOSH, DPSE. NIOSH [1998]. Polycyclic aromatic compounds: Method 5800. In: Eller PM, Cassinelli ME. Eds. th NIOSH Manual of Analytical Methods, 4 ed., 2nd Supplement. Cincinnati, OH:National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 98-

METHOD WRITTEN BY:

Larry B. Jaycox, Ph.D. NIOSH/DPSE

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition