Optimization of the geometry of a double-path spray chamber for inductively coupled plasma-atomic emission spectrometry by computer simulation and an evolutionary strategy

Abstract

Computational fluid dynamics (CFD) is used to investigate the analytical performance of variously sized inductively coupled plasma (ICP)-double-path spray chambers (Scott-type) and for the optimization of the geometry of the spray chamber using an evolutionary strategy. It can be seen from the simulation of the aerosol transport in chambers of various lengths that shorter chambers have better characteristics. This result was confirmed experimentally. A higher mass flow rate at the outlet of the chamber (aerosol yield) is obtained by reducing the diameter of the inner tube and keeping the other dimensions constant. An evolutionary strategy in combination with CFD was applied in order to find the optimum geometry for this type of chamber. For the evaluation of the virtual chambers the development of a quantitative objective function was necessary. The search for the best chamber geometry was then performed by searching for the global maximum of this function. As result, a modified ICP-double-path chamber with a much better analytical performance than that of the initial one was obtained. Replacing the original chamber by the optimized one, in the same inductively coupled plasma-atomic emission spectrometry instrument, resulted in the detection limits being lowered by a factor of 2–6 depending on the element. The combination of CFD and evolutionary algorithms can be used as a new and powerful tool for the optimization of various analytical flow systems.