Flow Injection Online Coupled With Atomic Absorption Spectrometry

Separation and preconcentration is one of the most important steps for the analysis of trace elements. The sensitivity of atomic absorption spectroscopy (AAS) can be effectively improved by various separation and preconcentration methods. But the conventional methods are time-consuming and labor-intensive, require a large volume of sample or toxic solvents, and suffer great risks of contamination and analyte loss. With on-line operation using flow injection (FI) techniques, the above drawbacks can be overcome to a great extent, while separation and preconcentration can be further enhanced in trace metals.The purpose of our work is to develop a simple, cost-effective, and sensitive method for the determination of trace metals in a variety of matrixes by FI on-line preconcentration coupled with FAAS. The knotted reactor is introduced to FI-FAAS as the preconcentration device, and sequentially developed the methods of continuous flowing, air segment insertion and novel MSP (multiplexed sorption preconcentration procedure). Seven chemical systems are tested including NH₃·H₂O and H₃PO₄ precipitation sorption-dissolution, APDC, Dithione and DDTC solid extraction and other systems for the determination trace metals in the solution.The EFs (efficient factors) are 21.0 for lead and 22.0 for copper respectively. With a sample loading flow rate of 4.4ml·min^-1 and preconcentration time of 90s, the detection limits (3s) are found to be 20.3μg·L^-1 and 6.5μg·L^-1 for copper and lead respectively. The precisions (RSD, n=11) are found to be 2.7%, at the level of 0.20mg·L^-1 of Cu (Ⅱ), and 3.6% at the level of 0.50mg·L^-1 of Pb(Ⅱ). The proposed method has been successfully applied to the determination of Cu (Ⅱ) and Pb( Ⅱ) in various samples.The process of FI-AAS, the prospect of the application and the development of this method are also discussed in the paper.