Page:NIOSH Manual of Analytical Methods - 7702.pdf/2

 LEAD BY FIELD PORTABLE XRF: METHOD 7702, Issue 1, dated 15 January 1998 - Page 2 of 4 REAGENTS:

EQUIPMENT:

1. None

1. Sampler: Mixed cellulose ester filter, 0.8-µm pore size, 37-mm diameter, with cellulose backup pad, in a closed-faced cassette filter holder. 2. Personal sampling pump, 1 to 4 L/min, with flexible connecting tubing. 3. Field portable, L-shell X-Ray Fluorescence (XRF) instrument with a Cadmium-109 source. 4. Filter sleeve: thin cardboard with 37-mm dia. cut out, and covered with a light adhesive between two pieces of acetate (Mylar™) (NITON, Bedford, MA, or equivalent). NOTE: Material must be transparent to X-ray. 5. Filter test platform to hold the filter (specific to instrument). 6. Forceps 7. Thin film standard reference materials from 15 µg/cm2 to 150 µg/cm2 (Micromatter Co., Deer Harbor, WA), or equivalent [7,8].

SPECIAL PRECAUTIONS: None

SAMPLING: 1. 2.

Calibrate each sampling pump with a representative sampler in line. Sample at an accurately known flow rate (1 to 4 L/min) for a total sample size of approximately 1000 L. Do not exceed a filter loading of 2 mg total dust.

SAMPLE PREPARATION: 3.

4. 5.

With forceps, transfer the MCE filter without the backup pad to a filter sleeve. The sleeve material must be transparent to X-rays (see EQUIPMENT, Item 4). NOTE: Take special care when removing the filter from the backup pad to avoid loss of leadcontaining dust. Place the filter into 37-mm opening and seal with Mylar™ film to prevent losses and allow undisturbed analysis of the filter. Place the sealed filter onto the filter test platform of the instrument for analysis. NOTE: The NITON® 700 Series XRF has a filter testplatform that allows for three readings with no substrate effect.

CALIBRATION AND QUALITY CONTROL: 6.

Start XRF and allow a 30-minute warm-up period. The instrument will conduct an internal selfcalibration. 7. Using thin film standards [8], verify the internal calibration to within ± 5% of the calibration standard. 2 Use a minimum of three standards at concentrations of 15 µg/cm , 150 µg/cm2, and one standard concentration between these two values. 8. Restart the instrument as needed to assure instrument accuracy prior to sample analysis. NOTE: When the thin film standard measurements are not within the specified parameters, the instrument may need to be recalibrated at the factory. 9. Analyze one thin film standard every 2 hours to check for instrument drift. 10. Repeat step 7 when all analyses are completed as a post-calibration check. MEASUREMENT: NIOSH Manual of Analytical Methods (NMAM), Fourth Edition