FLUORIDE in urine: METHOD 8308, Issue 2, dated 15 August 1994 - Page 3 of 4 8.
Run a spiked urine control specimen with every 10 specimens to maintain quality assurance. NOTE: Urine used for spiked controls must be analyzed before use to determine background fluoride concentration.
MEASUREMENT: 9. 10. 11. 12.
Add 10 mL well-mixed urine and 10 mL TISAB to a 50-mL plastic beaker. Place a small stirring bar into beaker and mix continuously on a magnetic stirrer at room temperature. Immerse electrodes. Allow sample to mix for 2 to 3 min and then record millivolt reading. Rinse electrodes and stirring bar thoroughly with distilled water and wipe dry with tissue before next sample analysis.
CALCULATIONS: 13. 14.
Convert the millivolt readings to fluoride concentration using the calibration graph. Express fluoride concentration as mg F /g urinary creatinine.
GUIDES TO INTERPRETATION: Urine concentrations of fluorides in normal non-occupationally exposed workers have been reported to range from 0.2 to 3.2 mg/L depending on dietary intake [6]. Preshift levels of less than 4 mg/g creatinine and post-shift levels of less than 7 mg/g creatinine appears to protect workers against bony fluorosis [7]. NIOSH has recommended that post-shift urine specimens should not exceed 7 mg/L (corrected to a specific gravity of 1.024) and pre-shift specimens should not exceed 4 mg/L (1.024) [1,2]. The Biological Exposure Indices for fluoride are 3 mg/g creatinine prior to shift and 10 mg/g creatinine at end of shift [8].
EVALUATION OF METHOD: No formal method evaluation has been reported; however, Tusl [3] reported recoveries of added fluoride from 94 to 100%. Precision based on analysis of 25 specimens in triplicate is estimated to be better than Sr = 0.04.
REFERENCES: [1] [2] [3] [4] [5] [6]
[7]
Criteria for a Recommended Standard...Occupational Exposure to Inorganic Fluorides, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 76-103 (1976). Criteria for a Recommended Standard...Occupational Exposure to Hydrogen Fluoride, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 76-143 (1976). Tusl, J. Direct determination of fluoride in human urine using fluoride electrode, Clin. Chim. Acta, 27, 216-218 (1970). NIOSH Manual of Analytical Methods, 2nd. ed., V. 1, P&CAM 114, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-157-A (1977). Tietz, N. W. Fundamentals of Clinical Chemistry , 2nd ed., W. B. Saunders Co., Philadelphia, PA, 994-999 (1976). Baselt, R. C. Biological Monitoring Methods for Industrial Chemicals , Biomedical Publications, Davis, CA, 140-143 (1980). Lauwreys, R. R. Industrial Chemical Exposure: Guidelines for Biological Monitoring , Biomedical NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
