Analysis of Copper in an Aqueous Solution by Ion-exchange Concentrator and Laser-induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy in composition analysis of materials has many advantages over other analytical methods. Its simple-or-no sampling procedure is a key advantage. The LIBS has been applied to liquid samples, although direct analysis of liquids is difficult because of weak plasma generation. An ion exchange membrane is used in this work to develop a real time monitoring method of metal ions in water. The chelating-resin based filter membrane was used to capture and concentrate copper ions from water. The samples were filtered under reduced pressure for faster filtration. The captured copper ions on the membrane were analyzed by LIBS. A series of copper solutions and mixtures were examined to establish the proper analytical conditions. The plasma emission intensity of copper generated from the thin layer of the membrane was investigated to determine the spectroscopic parameters for a practical real-time water monitoring. The copper ion collected on the membrane can be free of matrix effect from other ions in the original samples, and has provided the consistent analytical results in the mg/L concentration range. The laser power of each ablating pulse is very critical to obtain a proper analytical dynamic range, especially when the copper captured layer is thicker than the depth of one pulse laser can ablate. Tap water was used to analyze and evaluate the feasibility of this method. The amount of copper in the tap water was shown to depend on the retention time of water in copper pipes of the building pluming system.