Flow Injection On-line Preconcentration Coupled With Microwave Plasma Torch-atomic Emission Spectrometry For The Determination Of Metal Elements

The analysis of metals is very important in many fields such as modern medicine, pharmacy, life science, food science, material science, geology, chemical engineering and environmental monitoring. More and more attention has been paid to the determination of metals in recent years. Microwave plasma torch-atomic emission spectrometry (MPT-AES) is a new automated spectrometric instrument. As a source of AES, MPT has high stabilities and strong excitation powers. Most metals can be determined with MPT-AES. Compared with inductively coupled plasma-atomic emission spectrometry (ICP-AES), MPT-AES has much lower capital of operational cost.Flow injection analysis (FIA) is a new continuously analytical technology with many advantages, e.g. automatic operation, high analysis speed, high precision, and various appilicabilities. FIA is an ideal method for automatic monitoring and process analysis. It is an effective method for improving selectivity and sensitivity to couple FIA with preconcentration techniques, which has been proved by many authors.In the present work, a method for the determination of metals has been established by coupling FIA and ion exchange column preconcentration with MPT-AES. The adsorption capacity of ion exchange resins, sample acidity, sample flow rate, sample loading time, eluent concentration, eluent flow rate, and effect of diverse ions have been investigated. Under the optimal experimental conditions, the method is applied to the determination of cobalt and nickel in ten kinds of tea samples from market, indicating that the explored method is an effective method for the determination of cobalt and nickel in tea samples. For the determination of rare earths, an anion exchange resin is employed in the preconcentration step. An FIA on-line MPT-AES method combined with anion exchange resin preconcentration has been explored to the analysis of four REEs, lanthanum, cerium, neodymium, yttrium, in seven high purity REE oxides samples. Results show that the method can be successfully applied to the determination of the four metals in commercial REE oxides samples.Furthurmore, FIA has been combined with di(2-ethylhexyl) phosphoric acid (D2EHPA) resin preconcentration and MPT-AES to determine lanthanum, cerium, neodymium, and yttrium in the presence of a complexing agent, EDTA. Sample pH, sample flow rate, sample loading time, eluent flow rate, eluent concentration, EDTA flow rate, and EDTA concentration have been studied and optimized. The explored method is a highly selective and sensitive one for the separation and determination of REEs.The explored FI on-line preconcentration-MPT-AES method in the present work is effective when used to the determination of metals. It can not only improve sensitivity, automatic operation, but also improve analytical performance. Moreover, simple instrumental conditions and cheap reagents are employed in the method, so it may be used extensively in future determination.