Page:NIOSH Manual of Analytical Methods - 7501.pdf/3

 SILICA, AMORPHOUS: METHOD 7501, Issue 3, dated 15 March 2003 - Page 3 of 8 EQ UIP M EN T - c on t.: 17. 18. 19. 20. 21. 22. 23. 24.

Volumetric flasks, 1-L. Desicca tor. Bottle, 1-L, with ground glass s topper. Drying oven. W ash bottle, polyethylene. Mortar and pestle, agate. Rubber policeman. Beakers, 100-mL, with watchglass covers.

SPECIAL PRECAUTIONS: 2-Propanol is flamm able. Hydrochloric acid is corrosive and should be handled in a fume hood.

SAMPLING: 1. 2.

Calibrate each personal sampling pump with a representative sampler in line. Sam ple at 1 to 3 L/min (total and area), 1.7 L/min (nylon cyclone) or 2.2 L/min (HD) for a total sam ple size of 50 to 400 L. NOT E 1: Do not allow the cyclone to be inverted at any time. Turning the cyclone to anything other than a horizontal orientation may deposit over-sized material from the cyclone body onto the filter. NOT E 2: A single sa m pler/flow rate s hou ld be u sed for a g iven applica tion. Sa m pling fo r both crystalline silica and coal mine dust should be done in accordance with the ISO /CE N/A CG IH/A ST M resp irable a eros ol sam pling convention. Flow rates of 1.7 L/min for the Dorr-Oliver nylon cyclone and 2.2 L/min for the Higgins-Dewell cyclone have been found to be optimal for this purpose. Outside of coal mine dust sampling, the reg ulatory agencies currently use these flow rates with the Do rr-Oliver cyclone in the United States and the Higgins-Dewell sampler in the United Kingdom. Though the sampling recomm endations presented in a NIOSH Criteria Document have been form ally acce pted by MS HA for coal m ine du st sa m pling, the Dorr-O liver cyclone a t 2.0 L/min with 1.38 conversion factor is currently used in the United States for the purpose of m atch ing an earlier s am pling convention [6]. In any case, a single sam pler/flow rate should be used in any given application so as to eliminate bias introduced by differenc es b etwe en s am pler types an d sa m pler convention s [3].

SAMPLE PREPARATION: 3. 4.

5.

Ash the sam ple filter in a 100 -m L be aker in the LT A ac cording to m anu facturer's instru ctions. After ashing, carefully (so as to avoid loss of sam ple) add 50 m L 2% HC l to each beake r. Cover the beaker with a watchglass. Agitate in an ultrasonic bath for at least 3 min (until the agglom erated particles are broken up). W ash the und erside of the watchglass with distilled water, collecting the was hings in the sam e beak er. Place a 25-m m PVC filter in the filtration apparatus. Attach the funnel secu rely over the entire filter circumference. W ith no vacuum, pour 2 to 3 mL deionized water onto the filter. Pour the sample suspension from the beaker into the funnel, and apply vacuum. After the transfer, rinse the beaker several times with deionized water and add rinsings to funnel for a total volume of 20 mL. Allow the suspension to settle for a few minutes prior to filtration. Do not wash the chimney walls or add deionized water to the chimney after filtration has begun. Rinsing the chimney can disturb the thin layer depo sition. W hen filtration is com plete, k eep vacuum on until filter is dry. Rem ove the filter with forceps and attach it to the sample holder for XRD analysis.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition