Saturated Solution of PbSO₄ as Standard Stock Solution and Its Applications in Analytical Spectroscopy: Screening Analysis of Lead in Natural Water and Usnea longissima

Abstract

A saturated PbSO₄ aqueous solution, which was prepared by dissolving commercially available solid PbSO₄ in doubly distilled water, was employed as a standard stock solution of lead for the visual colorimetric determination of lead in water and atomic fluorescence spectrometric determination of lead in whole Usnea longissima (i.e., Methuselah's beard lichen). The concentration of lead in this saturated solution is theoretically calculated to 27.8 mg/L by using the solubility product constant of PbSO₄ at 25°C. The standard solution series is by further dilution of the saturated solution. A validation experiment proved the feasibility of using the saturated solution as the standard stock solution of lead. The experimental conditions, mainly the temperature, that affect the equilibrium of precipitation–dissolution in the saturated solution were investigated. The saturated PbSO₄ solution was proved to be accurate enough for the purpose of screening analysis of lead in these samples.

Keywords:

• Atomic fluorescence spectrometry
• hydride generation
• lead sulfate
• Usnea longissima
• visual colorimetry
• water

Acknowledgments

Xiandeng Hou is grateful to the Ministry of Education of China for financial support through grants NCET‐04‐0869. The authors thank Peng Wu and Guanglei Cheng of the Analytical & Testing Center of Sichuan University for their assistance in obtaining the ICP‐MS and GF‐AAS data, respectively.

Notes

The authors were invited to contribute this paper to a special issue of the journal entitled “Undergraduate Research and Education in Spectroscopy.” This special issue was organized by Associate Editor David J. Butcher, Professors of Chemistry at Western Carolina University, Cullowhee, North Carolina, USA.