Page:NIOSH Manual of Analytical Methods - 5524.pdf/4

METALWORKING FLUIDS (MWF) ALL CATEGORIES: METHOD 5524, Issue 2, dated 29 December 2014 - Page 4 of 10

SAMPLE PREPARATION AND MEASUREMENT: 13. Solubility test of bulk MWF: a. Shake the container of bulk MWF to ensure that a homogeneous sample is obtained. b. Place 10 mL of the ternary solvent blend in a 20-mL glass vial. c. Using a large-bore gas-tight syringe, inject 50 µL of the bulk MWF into the ternary solvent blend. Cap the vial and shake as necessary to dissolve the MWF. The fluid is soluble if the resulting solution is clear and free of precipitates and phase separation. d. If the MWF is soluble in the ternary blend, the samples can be extracted with the ternary blend. 14. Wipe dust from the external surface of each filter cassette (containing either samples or blanks) with a moist paper towel to minimize contamination. Discard the paper towel. 15. Remove the top and bottom plugs from the filter cassette. Equilibrate the filters (in the cassettes) for no more than 2 hours in a desiccator that uses calcium sulfate. 16. Remove from the desiccator. Equilibrate for at least 1 hour in the balance room or chamber. 17. Remove the cassette band, pry open the cassette, and remove the filter gently to avoid loss of sample. NOTE: If the filter adheres to the underside of the cassette top, very gently lift it away by using the dull side of a scalpel blade. This must be done carefully or the filter will tear. 18. Weigh and record (steps 5b through 5d) the post-sampling weight of each filter, W2 (mg) and blank, B2 (mg). Record anything remarkable about the filter (e.g., overload, leakage, wet, or torn). Perform the extraction as soon as possible. Store in a clean dust free environment until ready to perform the extraction, etc. EXTRACTION: 19. Perform all extractions in an exhaust hood. General guidelines (see NOTE below): NOTE: Samples weighing less than 0.4 to 0.5 mg (for a 1 m3 sample) may be extracted as desired. The reason that the cutoffs of 0.4 and 0.5 mg (per 1000 L sample) have been specified is to assure compliance with the occupational exposure limit (OEL). If the gross sample weight indicates that the OEL has not been exceeded, there may be no reason to extract the sample. Otherwise, the usefulness of any extraction data obtained at levels less than 0.4 to 0.5 mg per sample is guided by the limit of quantitation (LOQ) of the extraction procedure. Extraction data obtained at levels between the limit of detection (LOD) and the LOQ of the extraction procedure should be used with appropriate caution due to the imprecision associated with such data. 20. Do not presume that a fluid that is soluble only in the binary-blend should be extracted using only the binary blend. The possibility of mixed exposures always dictates that the extraction procedure with both the binary and ternary solvent blends should be followed. If the weights of samples exceed the amount expected to be collected at the REL, e.g., 0.4 mg (thoracic fraction) or 0.5 mg (‘total’ aerosol) for a 1 m3 air sample, then extract the samples and blanks as follows: a. Place each filter (membrane side up) in the filter funnel assembly connected to the vacuum source. b. Pour one 10-mL aliquot of the ternary solvent down the inside wall of the funnel over the filter. Allow the solvent to contact the filter for no more than 5 to 10 minutes. Remove the solvent under slight vacuum. c. Pour one 10-mL aliquot of the binary solvent down the inside of the funnel over the filter. Allow the solvent to contact the filter for no more than 5 to 10 minutes. Remove the solvent under slight vacuum. d. Pour a second 10-mL aliquot of the ternary solvent down the inside of the funnel over the filter. Allow at least 30 seconds of contact time. Remove the solvent under slight vacuum. Wash the inner wall of the filter funnel with 1 to 2 mL of the ternary blend contained in a PTFE wash bottle. Remove the solvent under slight vacuum. NIOSH Manual of Analytical Methods (NMAM), Fifth Edition