Microwave-assisted solid sampling system for Hg determination in polymeric samples using FF-AAS

Abstract

In this work, a new portable device based on a monomode microwave applicator was developed and applied for microwave-assisted solid sampling analysis coupled to flame furnace atomic absorption spectrometry (MW-SS-FF-AAS). As an example of application, Hg was determined in polymer samples in order to demonstrate the feasibility of the proposed system. Polymeric samples were weighed directly on a quartz boat, containing a microcrystalline cellulose pellet wetted with 6 mol L−1 NH4NO3 solution, which was introduced into the microwave system for the combustion step. Oxygen flowed continuously through the quartz tube for sample combustion, as well as to carry the combustion products to the flame furnace (FF) atomizer. Microwave irradiation was kept on up to sample ignition (generally <5 s). After that, microwave was turned off and atomic absorption signals were integrated. The instrument calibration was possible using aqueous reference solutions after optimization of some operational conditions such as mass of combustion aid, volume of igniter, oxygen flow rate, FF tube design, flame stoichiometry, and sample mass. Under optimized conditions, the LOD and LOQ were 0.2 and 0.7 μg g−1, respectively, which were suitable for Hg determination at low concentration in polymers. In addition, no statistical difference was observed between the results obtained by MW-SS-FF-AAS and the certified values of certified reference materials (ERM EC 681k and ERM EC 680k). The proposed microwave-assisted solid sampling system is portable and might be easily adapted to any conventional atomic absorption spectrometer, increasing the range of applications of this well-known technique.