Rapid Analysis of Heavy Metals in Coastal Seawater Using Preconcentration with Precipitation/Co-precipitation on Membrane and Detection with X-Ray Fluorescence

Abstract

Membrane pre-concentration methods coupled with hydroxide and sulfide precipitation/co-precipitation and X-ray fluorescence (XRF) detection have been developed for the determination of heavy metals (Fe, Ni, Mn, Cu, Zn, Pb) in coastal seawaters. The heavy metal ions in seawater samples can react with hydroxide or sulfide solution added to form hydroxide/sulfide precipitates. Then the precipitates containing target metals were filtrated on a membrane and directly detected with a portable XRF detector. Under the optimized conditions, the heavy metals in seawater samples were detected by the two type precipitation methods in the linear ranges of 12.5-400 mu g L-1 with a quantification limit of 12.5 mu g L-1. The RSDs (n=7) of the two type of precipitation methods were 3.7%-6.4% for a sample containing 100 mu g L-1 of each metal. The detection limits were 1.32-7.84 mu g L-1 for hydroxide precipitation method and 1.94-11.0 mu g L-1 for sulfide precipitation method. The proposed methods were successfully applied to determine the heavy metals in seawater samples obtained from Xiamen coastal sea area and Jiulongjiang Estuary. Based on whether or not the samples were acidified and filtered before or after acidification, the established methods were applicable to the fast and on-field analysis of dissolvable, dissolved and free heavy metals in coastal and estuary water samples.