Page:NIOSH Manual of Analytical Methods - 8003.pdf/3

LEAD IN BLOOD AND URINE: METHOD 8003, Issue 2, dated 15 August 1994 - Page 3 of 4 NOTE: If the patient is receiving EDTA therapy or if blood specimens are collected in tubes containing Na 2 EDTA as anticoagulant, add 50 µL 1.5 M CaCl 2 immediately before adding the MIBK [7].

CALIBRATION AND QUALITY CONTROL: 7. Prepare 6 working standards in deionized water in the range 10 to 150 µg/100 mL Pb by dilution of calibration stock solution with 2% (w/v) HNO 3. Prepare fresh daily. Example : 0.4 mL calibration stock stolution diluted to 1 L = 40 µg per 100 mL. 8. Analyze the working standards (steps 4, 5, 6, 12, and 13). 9. Prepare a calibration graph. Plot concentration (µg/100 mL) vs. absorbance of working standard, corrected for reagent blank. 10. Maintain standardization by analyzing a standard after every 5 samples. 11. Run a spiked control or pooled sample from exposed workers or commercial control every 10 samples or at least 3 per study. NOTE: Blood or urine lead background levels must be determined before spiked controls are prepared.

MEASUREMENT: 12. Set the atomic absorption spectrophotometer and lamp conditions as recommended by the manufacturer and as given on page 8003-1. Aspirate water-saturated MIBK and reduce acetylene flow until a stoichiometric flame with minimum background is obtained (< 0.01 absorbance). Record this reading. 13. Aspirate each sample and blank. Record maximum absorbances. NOTE: Samples with absorbance values greater than 0.35 must be diluted with MIBK and reanalyzed. Apply the appropriate dilution factor in calculations.

CALCULATIONS: 14. Calculate net absorbance (difference between the maximum absorbance of MIBK and the absorbance of the sample or blank). 15. Using metals, determine blood and urine lead levels in the samples (W s) and average reagent blanks (B) from the calibration graph. 16. For urine samples, report µg Pb/g creatinine. For blood samples, report µg Pb/g whole blood.

GUIDES TO INTERPRETATION: Blood lead concentrations for healthy adult suburbanites is 7 to 22 µg/100 g whole blood [2]. Urine has a wider range, 4 to 270 µg/g creatinine, for the same population; however, most normal values should be near 16 to 60 µg/g creatinine [4]. Blood lead values are commonly used for biological monitoring. A blood lead value above 40 µg/100 g is indicative of excess exposure and one above 60 µg/100 g requires removal from exposure [8]. EVALUATION OF METHOD: Forty-two blood specimens were spiked at levels of 25 to 200 µg/100 mL. Recoveries were 94 to 106%, averaging 100% [7]. For urine, 25 specimens were spiked at concentrations from 10 to 100 µg/mL. Recoveries averaged 100% (range 95 to 106%) [7]. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94