Page:NIOSH Manual of Analytical Methods - 5524.pdf/5

 METALWORKING FLUIDS (MWF) ALL CATEGORIES: METHOD 5524, Issue 2, dated 29 December 2014 - Page 5 of 10

e.	 Turn off the vacuum to the filter funnel. f.	 Carefully remove the filter from the filter funnel, place it on the clean metal screen, and allow to dry on the metal screen for at least 2 hours in a fume hood. Do not remove the filter from the funnel while vacuum is applied or the filter may delaminate. NOTE:	 One metalworking fluid, Glacier (Solutia Chemical, St Louis), was insoluble in the ternary blend but was soluble in the binary blend. Tests have shown that this fluid is extracted efficiently from the filters using steps 20a through 20e [5]. 21.	Weigh each filter, including field blanks, following steps 5a through 5d. Record the post-extraction weight, W3 (mg), of the extracted sample filters and B3 (mg), for the extracted blank filters. Record anything remarkable about the extracted filter (e.g., torn, wet, delamination, etc.). CALCULATIONS: 22.	Calculate the concentration of ‘total’ aerosol or thoracic fraction, C (mg/m3), in the air volume sampled, V (L):

(W2 − W1 ) − ( B2 − B1 ) * 103 L / m3 C= ,( mg / m3 ) V where:	W1 = mean tare weight of filter before sampling (mg) (step 5) W2 = mean post-sampling weight of sample-containing filter (mg) (step 18) B1 = mean tare weight of all blank filters (mg) (step 5) B2 = mean post-sampling weight of all blank filters (mg) (step 18) 23.	Calculate the concentration of extracted MWF aerosol CMWF (mg/m3), in the air volume sampled, V (L):

C MWF =

(W2 − W3 ) − (B2 − B3 ) * 103 L / m3 ,( mg / m3 ) V

where:	W2 = mean post-sampling weight (pre-extraction weight) of sample-containing filter (mg) (step 18) W3 = mean post-extraction weight of sample-containing filter (mg) (step 21) B2 = mean post-sampling weight of all blank filters (mg) (step 18) B3 = mean post-extraction weight of all blank filters (mg) (step 21) 24.	Report the concentration C as ‘total’ aerosol or thoracic fraction weight; report the concentration CMWF as the weight of the MWF aerosol. EVALUATION OF METHOD: The ‘total’ weight procedure permits an estimate of the ‘total’ collected particulate aerosol, including nuisance dust, airborne metal particulate and metal working fluid. If the extraction procedure is used, the technique permits an estimate of the ‘total’ collected metalworking fluid to which the worker is exposed. The development of the ternary solvent used in this method is described in reference 3. This method was initially tested with representative samples of straight, soluble, semi-synthetic, and synthetic metalworking fluids (MWFs). Samples were spiked onto tared polytetrafluoroethylene (PTFE) membrane filters, stored overnight, and analyzed the following day. The samples were weighed, then the MWF was extracted from the filter with a 1:1:1 blend of dichloromethane:methanol:toluene. The fractions extracted (FE or mass recovered/mass spiked) exceeded 94% for all fluids extracted from the filters over the range from 200 µg to 815 µg for the straight fluid, from 223 µg to 878 µg for the soluble NIOSH Manual of Analytical Methods (NMAM), Fifth Edition