Determination of Pb in Waste Lead Mud by Laser Induced Breakdown Spectroscopy

The sample of waste lead mud was dried at 105℃ for 3 h and pulverized to pass through sieve with mesh of 0.075 mm. Portions of the pulverized sample were taken to mix thoroughly with graphite powder in the mass ratios from 1 to 4 to 1 to 29 to give total mass of 3.00 g for each portion. The mixtures were pressed and separated to give sample discs having 30 mm in diameter and 3 mm in thickness; and lead content of each disc was determined by laser induced breakdown spectroscopy (LIBS). The sensitive spectral line of 405.78 nm of lead was chosen as the analytical spectral line, and the width of sampling inlet and the delay time were chosen at 5.5, 4.0 μs respectively. Fitting linear relationship for Pb was found in the range within 10 000 μg·g^-1. Value of detection limit found was 345.2 μg·g^-1. ICP-AES was applied to determine lead in a same sample as a check for the LIBS determination. It was shown by the comparative study that obvious deviations were observed between the results of LIBS and ICP-AES, showing an increase of relative deviation from ca. 1.3% to ca. 15% as the lead content decreases from ca. 9 000 μg·g^-1 to ca. 1 500 μg·g^-1, giving an average relative deviation of 6.80%.