Time-resolved particle image velocimetry and 3D simulations of single particles in the new conical ICP torch†
The prospective capabilities of the new ICP torch, with conical geometry, for ICP-MS/OES are investigated through experimental and numerical studies in comparison with a conventional torch. A combination of time-resolved particle image velocimetry and 3D computer simulations has been used to show the inherent advantages of the conical torch over conventional ones in terms of sample particle trajectory, velocity, and residence time. Based on a new technique, excited emission of mesophase spherical graphite particles was recorded using a high-speed camera for velocimetry and flow pattern characterization in any desired region of the torch. Additionally, a 3D magneto-hydrodynamic numerical model was developed to simulate the temperature, velocity, particle trajectories, and asymmetrical phenomena inside the torch. In addition to several important implications for single-particle ICP-MS/OES, the results show the conical torch to be superior to the conventional Fassel-type torch in several aspects. Due to the special geometry and higher power density of the conical torch, it is shown that the introduced particles exhibit better trajectories and the maximum ionization ratio is reached 3 times faster inside the central channel of the plasma, while using around 50% less gas and power. Based on the results, the conical torch is expected to potentially enhance particle detection accuracy and sensitivity, minimize particle loss, and break the particle throughput limitation of single-particle ICP-MS/OES.