Computer simulations of sample chambers for laser ablation–inductively coupled plasma spectrometry

The performance of several sample chambers was studied by means of computational fluid dynamics. The geometry and size was found to influence the gas velocity pattern as well as the extraction efficiency. The extraction efficiency of conventional ‘drum-shaped’ cells, in the volume range 3 to 100 cm3, was between 5 and 15% (number of particles), depending on the size and operating conditions such as gas flow rate, type of carrier gas. Optimized designs permitted as high as factor of six improved extraction efficiency. The use of helium improved the transport speed and extraction reproducibility of large volume cell. However, Ar showed better extraction efficiency than He, especially for the finer particles, due to a shorter mean free path, which mitigated nano-particle slipping.