Two test procedures for radon in drinking water: interlaboratory collaborative study

Two analytical methods for the determination of radon in water concentration were tested in a multilaboratory study with twenty-eight participating laboratories. Eighteen laboratories analyzed prepared samples by the liquid scintillation (LS) method, and twelve laboratories analyzed the same samples by the Lucas Cell (LC) method. A comparison of the grand averages for the three samples with the known values for those samples showed good accuracy for both methods. The accuracy index was not less than 94% for any of the three samples when analyzed by either method. Test results for the LS method showed better precision than test results for the LC method. The average repeatability (within-laboratory) precision for the LS method was 3.6 plus or minus 3.0% at 95% confidence and for the LC method it was 6.4 plus or minus 3.8% at 95% confidence. The average reproducibility (combined within-and between-laboratory) precision for the LS method was 10.2 plus or minus 4.2% at 95% confidence and for the LC method it was 17.6 plus or minus 4.2% at 95% confidence