Sensitive Determination of Trace Lead In Lake and Drinking Waters With Etaas Using Ni-NH₄H₂PO₄-NaOH Modifier

Abstract

A method has been developed for the direct determination of trace lead in Lake Michigan and two sources of drinking water. This method uses electrothermal atomic absorption spectrometry with platform atomization and a combined modifier of nickel, ammonium dihydrogenphosphate and sodium hydroxide (NI-NH₄H₂PO₄-NaOH). The optimal temperature program and modifier mass allowed quantitative stabilization of lead in water solution up to 1400°C. The characteristic mass and detection limit of the proposed method are 3.4 pg and 0.038 μg/1 for a 20 μ sample. The detection limit is 20 times lower than the USEPA standard method and 17.6 times lower than the manufacturer's recommended method (without modifier). The detection method can also tolerate interference of 0.6 mg/ml CI^–, 0.8 mg/ml SO₄ ^2– and 0.7 mg/ml CO₃ ^2–. The recoveries of lead spiked in the samples from Lake Michigan, a commercial spring water and a fountain were between 85% and 97%. The lead concetration in these samples were found to be in the range of 0.12–0.25 μg/l and 0.11–0.30 μ/l when sample volumes of 10 and 20 μl were used, respectively. Because of the low detection limit and the tolerance to interference, the proposed method offers a low-cost solution to the determination of trace lead in drinking and natural waters.

Key Words:

• Lead
• drinking water
• detection
• ETAAS