Page:NIOSH Manual of Analytical Methods - 7701.pdf/2

 LEAD by ULTRASONIC EXTRACTION/ASV: METHOD 7701, Issue 2, dated 15 March 2003 - Page 2 of 4 REAGENTS:

EQUIPMENT:

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1. Sam pler: Mixed cellulose ester filter, 0.8-:m pore size, 37-mm diameter, in cassette filter holder. 2. Personal sampling pump, 1 to 4 L/m in, with flexible connecting tubing. 3. Field-portable anodic stripping voltam m eter. 4. D i sp os ab l e o r r e ne wa ble v o l t a m m e t r y electrodes. 5. Ultrasonic bath, 50 watts m inimum power. 6. Power source for ultrasonic bath. 7. Pla stic centrifuge tubes, 50-mL, with screw caps. 8. Te st tube rac k (s ize to fit in ultras onic bath). 9. Plastic sam ple cell container. 10. Mechanical pipets (class A equivalent), 0.1-mL to 10-mL, as needed. 11. Pipet tips for mechanical pipets. 12. Forceps 13. Bottles, polyethylene, 100- to 1000-mL. 14. Vo lum etric flasks, 100-mL (for preparatory lab work). 15. Plastic rods.

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Nitric acid,* 10% (v/v) (Prepared from concentrated nitric acid, reagent grade; spectrosc opic grade if trace analysis). Distilled or deionized water (ASTM Type I or better [10]). Calibration stock solution, 1000 :g/m L Pb. Comm ercial standard, or dissolve 1.00 g Pb metal in minimum of 10 mL of 50% HCl and dilute to 1 L with 1% (v/v) HCl. Store in a polyethylene bottle. Stable for at least one year. Su pporting electrolyte : Aq ueous inert sa lt mixture such as 2.5 M NaCl and 0.25 M Na OH * (reagen t grad e or e quiva lent) [3,4 ]. Dissolved oxygen scavenger such as 0.25 M L-ascorbic acid (tissue culture grade or equ ivalent) [3,4]. Mercuric nitrate (reagent grade), if required (for Hg film electrodes). Certified Reference Materials (CRM s) for lead, prim ary or s econdary.


 * See SPECIAL PRECAUTIONS

NOTE: Clean all glassw are and reu sable plasticware with diluted nitric acid and rinse thoroughly with distilled or deionized water before use.

SPE CIAL PR ECAU TIO NS: Nitric acid and sodium hydroxide are irritants and m ay burn skin. Perform extractions in a well-ventilated area. W ear gloves and eye protection.

SAMPLING: 1. Calibrate each personal sampling pump with a representative sampler in the line. 2. Sample at an accurately known flow rate between 1 and 4 L/min for up to 8 h for a total sample size of 20 to 150 0 L fo r TW A m eas urem ents. Do n ot excee d a filter loa ding of ca. 2 m g total dust.

SAMPLE PREPARATION: 3. Open the cassette filter holders and, with forceps, transfer the samples and b lank s to separate 50-m L centrifuge tubes. Push the filters to the bottom of the tubes with plastic rods. 4. Add 10 mL of 10% HNO 3 and cap the centrifuge tubes. 5. Place centrifuge tubes in ultrasonic bath, and agitate at room tem perature for at least 30 min. NOT E 1: The water level in the bath should be above the level of liquid within the centrifuge tubes. NOTE 2: Proper performance of the ultrasonic bath should be demonstrated before use. This can be accomplished by checking recoveries of lead from performance evaluation materials. 6. Shake tubes for 5 to 10 sec, and allow to settle.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition