Page:NIOSH Manual of Analytical Methods - 7603.pdf/4

 QUARTZ in coal mine dust: METHOD 7603, Issue 3, dated 15 March 2003 - Page 4 of 7

6.

over the glass fiber filter. Clamp down the filter funnel. Add 5 mL 2-propanol and check for leakage. Rem ove the sample filter from the cassette. Fold it in half with the collection surface inside, then in quarters. Place the folded filter into the funnel. If necessary, push the filter to the bottom half of the funnel with a glass rod. Add 10 mL HC l solution, then 5 m L 2-propanol. Apply suction and continue until all of the liquid has been removed. Press the folded sa m ple filter on to the surface of the co llecting filter if neces sary to remove all the liquid. R em ove both filters and place in a porcelain crucible. Allow filters to air-dry. (2) If acid wash was not required, transfer filter samples and blanks to porcelain crucibles. (3) Loosely cover the crucibles and p lace in a muffle furnace. Hold for 2 h at 600 °C. After ashing, add several mL 2-propanol to the ash, scrape the crucible to loosen all particles and transfer to a 50-m L beaker. W ash the crucible several times and add wash to beaker. Add 2-propanol to the beaker to bring the volume to ca. 15 mL. Redeposit the sample residue as follows using the filtration apparatus with the 1.0-cm fun nel. W ith a slight vacuum applied, place a 25-mm glass fiber filter on the fritted base. Cut a 47-mm DM-450 filter in half. Superimpose one half over the other, glossy sides down, and place on the glass fiber filter. (The lower half of the DM-450 filter serves as a blank and is used in the reference beam of the infrared spectrometer). Position filter funnel, apply clamp and turn off vacuum. Add several mL 2propanol to the funn el. Check that the fun nel is securely and uniform ly clam ped. P lace sam ple beak ers into ultrasonic bath for at least 30 sec to ensure homogeneous dispersion. Remove a beak er, wipe exc ess wate r from the outside, trans fer slurry to the filtration funnel and reapply vacuum. During filtration, rinse the beaker twice with 2-propanol to remove all dust and add rins ings to fun nel. Co ntrol the filtration rate to ke ep the liquid near th e fun nel top during rinsing to avoid disturbing the dep osit. W hen the depth of liqu id in the funnel reaches ca. 4 cm above the filter, gently rinse the inside of funnel with 2-propanol and com plete filtration. Rem ove the clam p and lift off the fu nnel, taking care not to d istu rb and deposit. Release the vacuum. Define the deposit area by marking around the circumference using a pencil or scriber. This is especially important for standards or lightcolored sam ples. P lace the D M-450 filter ha lves in petri dishes and allow to air-dry.

CALIBRATION AND QUALITY CONTRO L: 7.

Prepare and analyze NIST SRM 1878a standard quartz filters. NOT E 1: Ca libration s tand ards are lim ited to NIST and U SG S c ertified stan dards of known purity, particle size, and sam ple-to -sample homogeneity. At least 12 materials, including 5 µm Min-U-Sil, previously used by laboratories throughout the United States and Canada, have been evaluated, and none has been fo und to be an accepta ble alternative to the certified standards cited within this method [3]. Standard reference materials should be corrected for ph ase purity. NOT E 2: Establishing traceability of secondary calibration standards to the specified NIST and USGS primary standards requires the use of measurement methods with better precision and accuracy than the XRD, IR and visible absorption spectrophotometry methods com m only used in the industrial hygiene field can provide. In addition, pa rticle size distribution measurem ents have considerable error. Therefore, the use of second ary calibration standards that are traceable to NIST and USGS certified standards is not appropriate. NOTE 3: NIST SRM 2950 calibration set ("-quartz) may be useful for preparing working standards at known concentrations. a. Place the flask containing the calibration stock solution in an ultrasonic bath for 30 to 45 min. b. Move the flask to a magnetic stirrer and stir slowly while the flask cools to room tem perature. Continue to stir slowly while preparing standards. c. Mount a DM-450 filter in the filtration apparatus in the same m anner used to redeposit the samples. Add 5 m L 2-propanol to th e fu nnel. W ithdraw an aliquot of the quartz suspension from the cente r of the flask . Draw liquid to the mark but do not attempt to adjust volume by draining pipet. Carefully wipe the outside of the pipet, then drain the suspension into th e filter fun nel. Rins e do wn th e inside wa ll of the pipet with a few m L of 2 -propan ol, draining the was hings into the filter funnel. Apply vacuum to complete the filtration. Prepare quartz standards to cover the range 10 to 25 0 µg per filter. d. Carry an additional set of these standards and media blanks through steps 5 and 6 to monitor for contamination and losses. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition