Page:NIOSH Manual of Analytical Methods - 5042.pdf/5

 BENZENE-SOLUBLE & TOTAL PARTICULATE (ASPHALT FUME): METHOD 5042, Issue 1, dated 15 January 1998 - Page 5 of 7

CALCULATIONS FOR TOTAL PARTICULATE: 3 12. Calculate the concentration of total particulate, C TP (mg/m ), in the air volume sampled, V (L).

CTP

where:

( W2

W1 )

( B2

B1 )

V

, mg/m 3

W1 = mean tare weight of filter before sampling (µg) W2 = mean post-sampling weight of sample-containing filter (µg) B1 = mean tare weight of field blank filters (µg) B2 = mean post-sampling weight of field blank filters (µg)

BENZENE-SOLUBLE FRACTION MEASUREMENT: 13. Condition clarification unit by rinsing the reservoir with 1.5 mL of benzene. Use nitrogen pressure to force the benzene through the frit. Appropriately dispose of the benzene rinse. 14. Extract benzene-soluble fraction. a. Add 3.0 mL benzene via a 3-mL volumetric pipet to the filter-containing test tube (step 11.e.) Recap the test tube. b. Place the test tube upright in beaker containing water to the same level as the liquid in the test tube. Place the beaker and test tube in ultrasonic bath and agitate for 20 minutes. c. Transfer benzene extract to conditioned clarification unit and force the extract through into a clean test tube, using nitrogen pressure as in step 13. Discard sampling filter and clarification unit. NOTE: Be sure the end of the clarification unit is well below the opening of the test tube to prevent sample loss by spattering. 15. Preweigh clean weighing cups by the weighing procedure in step 3. Record the mean tare weight, 3W or B3 (µg). NOTE: The weighing cup should already be prerinsed and dried as described in the Equipment section. a. Identify each tared weighing cup by labeling its place in the carrying rack. b. Transfer a 1.5-mL aliquot of the benzene extract via a 2-mL Mohr pipet to the tared weighing cup. NOTE: An aliquot may be taken from the remaining extract at this step if other analyses (e.g., polycyclic aromatic compounds) are to be performed on the sample. Apply the appropriate aliquot factor in calculations. 16. Place the weighing cup rack in a vacuum oven preheated to 40C. Apply vacuum until pressure in the oven is 7 to 27 kPa (50 to 200 mm Hg). Allow solvent to evaporate (about two hours). Release the vacuum by slowly opening a release valve that has an in-line filter to remove room dust. 17. Reweigh the weighing cup by the weighing procedure in step 3. Record the mean post-sampling weight, W 4 or B4 (µg). Also, record anything remarkable about the sample (e.g., overload, leakage, wet, spattering, etc.). 18. After weighing, clean the weighing cup as described in the Equipment section.

CALCULATIONS FOR BENZENE-SOLUBLE FRACTION: 3 19. Calculate the concentration of benzene-soluble fraction, C BSF (mg/m ), in the volume of air sampled, V (L):

CBSF

where:

[( W4

W3 )

( B4 V

B3 )]

2

, mg/m 3

W3 = mean tare weight of sample weighing cup (µg) W4 = mean post-sampling weight of sample weighing cup (µg) B3 = mean tare weight of field blank weighing cups (µg) B4 = mean post-sampling weight of field blank weighing cups (µg) NIOSH Manual of Analytical Methods (NMAM), Fourth Edition