This International Standard specifies a method for the determination of mercury in drinking, surface, ground and rain water using atomic fluorescence spectrometry. NOTE This International Standard may be applied to industrial and municipal waste water after an additional digestion step under appropriate conditions. The potential linear dynamic range is approximately to . In practice, the working range is often from to . Samples containing mercury at concentrations higher than the working range can be analysed following appropriate dilution of the sample. The method detection limit ( ) will be dependent on the selected operating conditions and calibration range. With high purity reagents, a of less than is obtainable. The relative standard deviation is typically less than for concentrations greater than twenty times the method detection limit. The sensitivity of this method is dependent on the selected operating conditions.