Page:NIOSH Manual of Analytical Methods - 5524.pdf/3

 METALWORKING FLUIDS (MWF) ALL CATEGORIES: METHOD 5524, Issue 2, dated 29 December 2014 - Page 3 of 10

CALIBRATION AND QUALITY CONTROL: 1.	Zero the microbalance before all weighings. Use the same microbalance for weighing filters before and after sample collection. Maintain and calibrate the balance with National Institute of Standards and Technology Class S-1.1 or ASTM Class 1 weights. 2.	Process at least three tared media blanks through the measurement process for ‘total’ aerosol and the extractable materials. PREPARATION OF FILTERS BEFORE SAMPLING: 3.	Number the backup pads with indelible ink and place them, numbered side down, in the filter cassette bottom sections. 4.	Pre-weigh the filters by the weighing procedure given in step 5. Record the mean tare weight of sample filters, W1 and field blanks, B1 (mg). 5.	Weighing procedure: a.	 Equilibrate the filters in an environmentally controlled weighing area or chamber for 1 hour (minimum.) b.	 Zero the balance before each weighing. Using forceps, pass each filter over a static neutralizer. Repeat this step if the filter does not release easily from the forceps or attracts the balance pan. (Static electricity can cause erroneous weight readings.) c.	 Weigh each filter until a constant weight is obtained (i.e., two successive weighings within 10 µg.) d.	 Record the mean of the last two weights to the nearest microgram. 6.	Assemble the filter in the 2- or 3-piece filter cassettes and close firmly so that leakage around the filter will not occur. Place a plug in each opening of the filter cassette. Place a cellulose shrink band around the filter cassette and allow to dry. Alternatively, use heavy duty elastic tape instead of the shrink band. Mark with the same number as the backup pad. SAMPLING: Bulks:	For solubility testing, obtain liquid samples of pure uncut bulk metal-working fluids (MWF) that are expected to be sampled in worker breathing zone. Place these samples in small (e.g., 10 mL) leak-proof glass container(s) that are sealed with a leak-proof PTFE-lined screwcap. Then place them inside of a resealable plastic bag and ship these samples to the laboratory along with the sample filter cassettes. Air: For collection of a thoracic sample, insert the cyclone into the inlet of a 3-piece cassette. For collection of a “total” sample, do not use the cyclone. 7.	Calibrate each personal sampling pump with a representative sampler in line. 8.	For thoracic measurements, sample at 1.6 L/min for 8 hours. For ‘total’ aerosol measurements, sample at 2 L/min for 8 hours. Do not exceed a total filter loading of approximately 2 mg. 9.	Submit at least 5 blank filter samples as field blanks and 3 filters for media blanks for each set of samples collected per day. Handle the field blanks in the same way as the field samples; i.e., open each in a non-contaminated environment, then close the sampler and ship it to the lab along with the remaining samples. Media blanks are not opened. 10.	Refrigerate all samples that are to be stored overnight (or longer) prior to shipment to the laboratory. Ship all samples in refrigerated containers to the laboratory via overnight express delivery service. 11.	Refrigerate the samples immediately upon receipt at the lab until ready for analysis. 12.	Analyze the samples within two weeks of receipt at the laboratory.

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition